CASES OF THE MONTH
DNAJB6 MYOPATHY: A VACUOLAR MYOPATHY WITH CHILDHOOD ONSET GERSON SUAREZ-CEDENO, MD,1,2 THOMAS WINDER, PhD,3 and MARGHERITA MILONE, MD, PhD1 1 Medical School, Department of Neurology, Mayo Clinic Foundation, 200 First Street SW, Rochester, Minnesota 55905, USA 2 Universidad de Antioquia, Medellin, Colombia 3 Prevention Genetics, Marshfield, Wisconsin, USA Accepted 24 October 2013 ABSTRACT: Introduction: DNAJB6 mutations cause an autosomal dominant myopathy that can manifest as limb-girdle muscular dystrophy (LGMD1D/1E) or distal-predominant myopathy. In the majority of patients this myopathy manifests in adulthood and shows vacuolar changes on muscle biopsy. Methods: Clinical, electrophysiological, pathological, and molecular findings are reported. Results: We report a 56-year-old woman, who, like 3 other family members, became symptomatic in childhood with slowly progressive limb-girdle muscle weakness, normal serum creatine kinase (CK) values, and myopathic electromyographic findings. Muscle biopsy showed vacuolar changes and congophilic inclusions, and molecular analysis revealed a pathogenic mutation in the DNAJB6 gene. Differences and similarities with previously described cases are assessed. Conclusions: Childhood-onset of DNAJB6 myopathy is more frequent than previously believed; congophilic inclusions may be present in the muscle of these patients. Muscle Nerve 49:607–610, 2014
Limb-girdle muscular dystrophies (LGMD) are genetically heterogeneous progressive myopathies characterized by predominant weakness of hipand shoulder-girdle muscles. At present, 5 proteins are known to cause autosomal dominantly inherited LGMD (LGMD1)1: myotilin (LGMD1A); lamin A/C (LGMD1B); caveolin 3 (LGMD1C); desmin (LGMD1D); and, more recently, DNAJ subfamily B member 6 (DNAJB6; LGMD1E; OMIM 603511).2,3 DNAJB6 mutations were identified very recently in families with the LGMD phenotype and muscle biopsy findings of rimmed vacuoles and cytoplasmic inclusions. They were linked previously to 7q36.4–6 LGMD linked to 7q36 has also been classified as LGMD1D (Human Gene Nomenclature Committee, HGNC 6576). The Online Mendelian Inheritance in Man (OMIM) database had previously used the symbol LGMD1D for LGMD mapping to 7q36, but, after the 105th ENMC Workshop,7 it was redesignated as LGMD1E, leaving the symbol LGMD1D to a form of LGMD due Abbreviations: CK, creatine kinase; DNAJB6, DNAJ subfamily B member 6; EMG, electromyography; Hsp, heat shock protein; LGMD, limb-girdle muscular dystrophy; VCP, valosin-containing protein Key words: congophilic inclusions; DNAJB6; LGMD1D; LGMD1E; limbgirdle muscular dystrophy; vacuolar myopathy Correspondence to: M. Milone; e-mail: [email protected] C 2013 Wiley Periodicals, Inc. V
Published online 29 October 2013 in Wiley Online Library (wileyonlinelibrary. com). DOI 10.1002/mus.24106
Limb-Girdle Muscular Dystrophy 1E
to desmin mutations (http://omim.org/entry/ 603511).8 To avoid the confusing nomenclature, we refer to this myopathy as DNAJB6 myopathy. DNAJB6 mutations also cause a predominantly distal vacuolar myopathy.3 Due to the pathological combination of rimmed vacuoles, cytoplasmic inclusions, and disorganized myofibrils, it has been indicated that DNAJB6 myopathy is a form of myofibrillar myopathy.9 The majority of patients reported so far have become symptomatic between the ages of 142 and 68 years,10 with the exception of a subject who was a slower runner in childhood.9 None of them had extraocular or bulbar muscle weakness or cardiac involvement. DNAJB6 is a highly conserved member of the Jproteins, also known as the heat shock protein (Hsp) 40 family, and consists of an N-terminal J domain and a C-terminal domain linked by the G/F D domain enriched in glycine and phenylalanine.2,3,5 Four pathogenic mutations have been identified so far in DNAJB6, p.Phe89Ile, p.Phe93Leu, p.Phe96Leu, and p.Phe96Ile, all occurring in the G/F domain.2,3,9 Here, we describe the clinical, electromyographic, pathological, and molecular findings in a patient with DNAJB6 myopathy due to p.Phe89Ile, affecting 4 generations of a family. CASE REPORT
A 56-year-old woman had difficulty running and keeping up with her peers when she was about 8 years of age. She was a slow runner, and could not participate in gym class due to weakness and “lack of coordination.” Around age 20 she noted slowly progressive proximal lower extremity weakness, which 15 years later extended to the proximal upper extremity muscles. She developed muscle atrophy in her legs, which had previously been described as “very muscular.” Additional symptoms included muscle stiffness that improved with activity, muscle cramps independent from activity, and dysphagia, for which she had undergone esophageal stretching multiple times. She had past history of unilateral lattice retinal degeneration. Several family members in 4 generations were affected by proximal muscle weakness MUSCLE & NERVE
April 2014
607
fibers, small globular congophilic deposits in most vacuoles, 2 or 3 cytochrome c oxidase–negative fibers per fascicle, and mild type 1 fiber predominance (Fig. 2). No necrotic or regenerating muscle fibers or inflammatory cells were present. Sequencing of DNAJB6 detected a known pathogenic heterozygous mutation c.265T>A (p.Phe89Ile). Sequencing of valosin-containing protein (VCP) and myosin heavy chain type 2 (MYH2) genes, which are known causes for autosomal dominant vacuolar myopathy, revealed no mutations. FIGURE 1. Pedigree of the DNAJB6 myopathy family. Affected subjects are marked in black. Arrow: proband; filled circle: early death; ?: lack of medical information.
(Fig. 1). In addition to the proband, a sister (III:6) and 2 other individuals (V:1 and V:3) became symptomatic in childhood with leg weakness and difficulty climbing stairs. All other affected family members had disease onset in adulthood. Subject III:3 was the most severely affected and became wheelchair-bound at age 50 and died at age 70. The proband’s father and his brother (II:1) remained ambulatory until death at age 62 of malignancy and approximately age 50 of unknown cause, respectively. The oldest living family member (III:4) is ambulatory at age 65. The paternal side of the family is of Native American and Scottish descent. The patient’s neurological examination revealed symmetric proximal muscle weakness, which was mild in the supraspinatus, infraspinatus, pectoral muscles, and hamstrings (MRC 4) and moderate in the iliopsoas, gluteus medius, and gluteus maximus (MRC 3.5), resulting in a waddling gait. She was unable to arise from supine to sitting unless she first rolled on her side. Strength in other muscles was preserved, including quadriceps and thigh adductors. The calf muscles were mildly atrophic, despite her ability to walk on toes. She had no action or percussion myotonia; the rest of the examination was normal. Serum creatine kinase (CK) values were normal, as were calcium and alkaline phosphatase. Electromyographic (EMG) study demonstrated small and polyphasic motor unit potentials, early recruitment, and few fibrillation potentials in proximal muscles; motor and sensory nerve conduction studies were normal. Video-fluoroscopic swallowing study, spirometry, electrocardiogram, and dobutamine stress echocardiogram findings were normal. Biopsy of the left gluteus medius showed muscle fiber size variability, numerous muscle fibers harboring vacuoles, most of which were lined by membranous material and were overreactive for acid phosphatase, focal irregular loss of oxidative enzyme reactivity in some vacuolated 608
Limb-Girdle Muscular Dystrophy 1E
DISCUSSION
We describe a patient from a 4-generation family affected by DNAJB6 myopathy, which became symptomatic in childhood with a limb-girdle phenotype and harboring a known pathogenic mutation, p.Phe89Ile. The patient described and the family member phenotypes share similarities but also differences from the cases reported so far. There was variability in age of disease onset, and 4 family members became symptomatic in childhood, suggesting that childhood onset of the myopathy, described previously in a single patient,9 is not rare. The 56-year-old proband, who also manifested in childhood, had very selective proximal muscle weakness that spared quadriceps and thigh adductors, muscles that have been described to be weak and radiologically involved early in previous reports of DNAJB6 myopathy.5,6,10 Our patient did not have a muscle MRI study, and therefore we cannot exclude subclinical involvement of thigh adductors and quadriceps, but the normal strength and size of these muscles 5 decades after onset of weakness would point away from significant fatty replacement. The patient had also abdominal wall muscle weakness, as suggested by her inability to arise from supine to sitting, an observation not reported previously in other DNAJB6 myopathy individuals. She had normal CK values, as observed previously in DNAJB6 myopathy, although more commonly there is a 2–5-fold increase in CK levels.3,5,6 The numerous rimmed vacuoles and associated congophilic inclusions were the dominant pathological features of her muscle biopsy. Rimmed vacuoles are a pathological feature of DNAJB6 myopathy, and intravacuolar filamentous inclusions have been detected by electron microscopy in some patients.5 However, the patient’s muscle biopsy displayed numerous intracellular congophilic inclusions that were easily detectable in Congo red–stained sections viewed under rhodamine optics (Fig. 2) and this, to our knowledge, is a novel finding. Trichrome-stained sections did not reveal dark cytoplasmic inclusions (Fig. 2B), which have been observed in other individuals with the MUSCLE & NERVE
April 2014
FIGURE 2. Muscle biopsy of the gluteus medius. (A, hematoxylin-eosin, and B, trichrome) Numerous rimmed vacuoles were present, as shown by arrows. No eosinophilic inclusions were present in trichrome-stained sections (B). (C) Over-reactivity for acid phosphatase. (D) Few muscle fibers showed focal loss of NADH reactivity. (E and F) Congophilic deposits were present within several vacuoles in Congo red-stained sections viewed under rhodamine optics. Bar 5 50.0 lm.
same myopathy.5,6,9 Her clinical, serological, and pathological features overlapped with other myopathies, such as VCP myopathy, which may also present with isolated limb-girdle weakness, rimmed vacuoles, and congophilic inclusions.11,12 Therefore, molecular analysis is the only tool that can provide a definite diagnosis. The observation of congophilic inclusions in this patient is of particular interest in light of the recently reported ability of the DNAJB6 protein to suppress the tendency of the polyglutamine peptides to form amyloid fibrils.13 DNAJB6, similar to other DNAJ family members, is a molecular chaperone of heat shock protein 70 (Hsp70); chaperones and co-chaperones protect proteins from irreversible aggregation during synthesis or at the time of cellular stress.14 On the basis of these observations, it could be speculated that the congophilic inclusions may be the result of protein aggregation secLimb-Girdle Muscular Dystrophy 1E
ondary to DNAJB6 protein loss of function, but further functional studies are needed to fully understand the pathogenesis of the disease. REFERENCES 1. Mitsuhashi S, Kang PB. Update on the genetics of limb girdle muscular dystrophy. Semin Pediatr Neurol 2012;19:211–218. 2. Sarparanta J, Jonson PH, Golzio C, Sandell S, Luque H, Screen M, et al. Mutations affecting the cytoplasmic functions of the cochaperone DNAJB6 cause limb-girdle muscular dystrophy. Nature Genet 2012;44:450–455, s451–452. 3. Harms MB, Sommerville RB, Allred P, Bell S, Ma D, Cooper P, et al. Exome sequencing reveals DNAJB6 mutations in dominantlyinherited myopathy. Ann Neurol 2012;71:407–416. 4. Speer MC, Vance JM, Grubber JM, Lennon Graham F, Stajich JM, Viles KD, et al. Identification of a new autosomal dominant limbgirdle muscular dystrophy locus on chromosome 7. Am J Hum Genet 1999;64:556–562. 5. Sandell S, Huovinen S, Sarparanta J, Luque H, Raheem O, Haapasalo H, et al. The enigma of 7q36 linked autosomal dominant limb girdle muscular dystrophy. J Neurol Neurosurg Psychiatry 2010; 81:834–839. 6. Hackman P, Sandell S, Sarparanta J, Luque H, Huovinen S, Palmio J, et al. Four new Finnish families with LGMD1D; refinement of the clinical phenotype and the linked 7q36 locus. Neuromuscul Disord 2011;21:338–344.
MUSCLE & NERVE
April 2014
609
7. Bushby KM, Beckmann JS. The 105th ENMC sponsored workshop: pathogenesis in the non-sarcoglycan limb-girdle muscular dystrophies, Naarden, April 12–14, 2002. Neuromuscul Disord 2003;13:80–90. 8. Greenberg SA, Salajegheh M, Judge DP, Feldman MW, Kuncl RW, Waldon Z, et al. Etiology of limb girdle muscular dystrophy 1D/1E determined by laser capture microdissection proteomics. Ann Neurol 2012;71:141–145. 9. Sato T, Hayashi YK, Oya Y, Kondo T, Sugie K, Kaneda D, et al. DNAJB6 myopathy in an Asian cohort and cytoplasmic/nuclear inclusions. Neuromuscul Disord 2013;23:269–276. 10. Sandell SM, Mahjneh I, Palmio J, Tasca G, Ricci E, Udd BA. ’Pathognomonic’ muscle imaging findings in DNAJB6 mutated LGMD1D. Eur J Neurol 2013 Jul 19. [Epub ahead of print] 11. Stojkovic T, el Hammouda H, Richard P, Lopez de Munain A, Ruiz-Martinez J, Camano P, et al. Clinical outcome in 19 French and
Spanish patients with valosin-containing protein myopathy associated with Paget’s disease of bone and frontotemporal dementia. Neuromuscul Dis 2009;19:316–323. 12. Kimonis V, Donkervoort S, Watts G. Inclusion body myopathy with Paget disease of bone and/or frontotemporal dementia. In: Pagon RA, Adam MP, Bird TD, editors. GeneReviews. Seattle, WA: University of Washington; 1993. 13. Ma˚nsson C, Kakkar V, Monsellier E, Sourigues Y, Harmark J, Kampinga HH, et al. DNAJB6 is a peptide-binding chaperone which can suppress amyloid fibrillation of polyglutamine peptides at substoichiometric molar ratios. Cell Stress Chaperones 2013 Aug 1. [Epub ahead of print] 14. Kampinga HH, Craig EA. The HSP70 chaperone machinery: J proteins as drivers of functional specificity. Nature Rev Mol Cell Biol 2010;11:579–592.
ENTECAVIR-ASSOCIATED MYOPATHY: A CASE REPORT AND LITERATURE REVIEW KAI YUAN, MD,1 GUOCHUN WANG, MD, PhD,1 ZHENGUO HUANG, MD,2 BING LIN, MD,1 HUIQIONG ZHOU, MD, PhD,1 and XIN LU, MD1 1 2
Department of Rheumatology, China–Japan Friendship Hospital, Yinghua East Road, Chaoyang District, Beijing 100029, China Department of Radiology, China–Japan Friendship Hospital, Beijing, China
Accepted 6 November 2013 ABSTRACT: Introduction: Entecavir, a nucleoside analog (NA), is effective for treatment of chronic hepatitis B virus (HBV) infection. Methods: We report the case of a patient we encountered with entecavir-associated myopathy. We also performed a literature review of myopathies associated with nucleoside analogs. Results: A 44-year-old man presented with a 3-month history of myalgia and progressive weakness. He had HBV infection and had received entecavir antiviral treatment for 5 years. Laboratory tests showed that serum creatine kinase levels were significantly elevated. Muscle histopathology showed abundant T-lymphocyte infiltration of muscle fibers, and HBV surface antigen and HBV core antigen were not present in muscle fibers. Entecavir-associated myopathy was subsequently diagnosed. The patient’s symptoms eventually resolved, and serum CK levels decreased rapidly after he stopped receiving entecavir treatments. Conclusions: Patients who receive NA therapy should be closely monitored for myopathic side effects. Muscle Nerve 49:610–614, 2014
Chronic infection by hepatitis B virus (HBV) affects more than 350 million people worldwide and can have serious consequences, including cirrhosis, hepatic failure, and hepatocellular carcinoma.1 Nucleoside analogs (NAs) and interferons are the first-line treatments for HBV. NAs include entecavir, Additional Supporting Information may be found in the online version of this article. This work was supported by the Beijing Science and Technology Committee (Z111107058811084). Abbreviations: ALT, alanine aminotransferase; AST, aspartate aminotransferase; ATP, adenosine triphosphate; CK, creatine kinase; HBV, hepatitis B virus; MANA, myopathies associated with nucleoside analogs; MHC, major histocompatibility complex; MMT, manual muscle testing; MRC, Medical Research Council; MRI, magnetic resonance imaging; NA, nucleoside analog; PM, polymyositis; STIR, short time inversion recovery Key words: creatine kinase; entecavir; hepatitis B; myopathy; nucleoside analog Correspondence to: X. Lu; e-mail: [email protected] C 2013 Wiley Periodicals, Inc. V
Published online 12 November 2013 in Wiley Online Library (wileyonlinelibrary. com). DOI 10.1002/mus.24118
610
Entecavir-Associated Myopathy
lamivudine, telbivudine, clevudine, and adefovir. The primary mechanism by which NAs act is to inhibit viral polymerase activity. Entecavir has proven to be effective and safe for HBV treatment, but the treatment has some side effects. Common adverse effects related to entecavir include headache, upper respiratory tract infection, upper abdominal pain, and flu-like symptoms. Most of these adverse effects are of mild-to-moderate severity.2 To our knowledge, entecavir-associated myopathy has not been reported. We describe a patient with entecavirassociated myopathy. We also review the literature regarding myopathies associated with nucleoside analogs (MANA) to find new information about their clinical and pathologic features, management, and prognosis. CASE REPORT
A 44-year-old man who had received entacavir therapy previously for chronic hepatitis B presented with a 3-month history of muscle pain and weakness in his lower extremities. He had a 20-year history of chronic hepatitis B infection and had been treated with entecavir for the HBV infection for the past 5 years on a stable dose of 0.5 mg/ day. He did not supplement the entecavir therapy with any other medication, and his blood HBV DNA levels had remained within the normal range (
DNAJB6 MYOPATHY: A VACUOLAR MYOPATHY WITH CHILDHOOD ONSET GERSON SUAREZ-CEDENO, MD,1,2 THOMAS WINDER, PhD,3 and MARGHERITA MILONE, MD, PhD1 1 Medical School, Department of Neurology, Mayo Clinic Foundation, 200 First Street SW, Rochester, Minnesota 55905, USA 2 Universidad de Antioquia, Medellin, Colombia 3 Prevention Genetics, Marshfield, Wisconsin, USA Accepted 24 October 2013 ABSTRACT: Introduction: DNAJB6 mutations cause an autosomal dominant myopathy that can manifest as limb-girdle muscular dystrophy (LGMD1D/1E) or distal-predominant myopathy. In the majority of patients this myopathy manifests in adulthood and shows vacuolar changes on muscle biopsy. Methods: Clinical, electrophysiological, pathological, and molecular findings are reported. Results: We report a 56-year-old woman, who, like 3 other family members, became symptomatic in childhood with slowly progressive limb-girdle muscle weakness, normal serum creatine kinase (CK) values, and myopathic electromyographic findings. Muscle biopsy showed vacuolar changes and congophilic inclusions, and molecular analysis revealed a pathogenic mutation in the DNAJB6 gene. Differences and similarities with previously described cases are assessed. Conclusions: Childhood-onset of DNAJB6 myopathy is more frequent than previously believed; congophilic inclusions may be present in the muscle of these patients. Muscle Nerve 49:607–610, 2014
Limb-girdle muscular dystrophies (LGMD) are genetically heterogeneous progressive myopathies characterized by predominant weakness of hipand shoulder-girdle muscles. At present, 5 proteins are known to cause autosomal dominantly inherited LGMD (LGMD1)1: myotilin (LGMD1A); lamin A/C (LGMD1B); caveolin 3 (LGMD1C); desmin (LGMD1D); and, more recently, DNAJ subfamily B member 6 (DNAJB6; LGMD1E; OMIM 603511).2,3 DNAJB6 mutations were identified very recently in families with the LGMD phenotype and muscle biopsy findings of rimmed vacuoles and cytoplasmic inclusions. They were linked previously to 7q36.4–6 LGMD linked to 7q36 has also been classified as LGMD1D (Human Gene Nomenclature Committee, HGNC 6576). The Online Mendelian Inheritance in Man (OMIM) database had previously used the symbol LGMD1D for LGMD mapping to 7q36, but, after the 105th ENMC Workshop,7 it was redesignated as LGMD1E, leaving the symbol LGMD1D to a form of LGMD due Abbreviations: CK, creatine kinase; DNAJB6, DNAJ subfamily B member 6; EMG, electromyography; Hsp, heat shock protein; LGMD, limb-girdle muscular dystrophy; VCP, valosin-containing protein Key words: congophilic inclusions; DNAJB6; LGMD1D; LGMD1E; limbgirdle muscular dystrophy; vacuolar myopathy Correspondence to: M. Milone; e-mail: [email protected] C 2013 Wiley Periodicals, Inc. V
Published online 29 October 2013 in Wiley Online Library (wileyonlinelibrary. com). DOI 10.1002/mus.24106
Limb-Girdle Muscular Dystrophy 1E
to desmin mutations (http://omim.org/entry/ 603511).8 To avoid the confusing nomenclature, we refer to this myopathy as DNAJB6 myopathy. DNAJB6 mutations also cause a predominantly distal vacuolar myopathy.3 Due to the pathological combination of rimmed vacuoles, cytoplasmic inclusions, and disorganized myofibrils, it has been indicated that DNAJB6 myopathy is a form of myofibrillar myopathy.9 The majority of patients reported so far have become symptomatic between the ages of 142 and 68 years,10 with the exception of a subject who was a slower runner in childhood.9 None of them had extraocular or bulbar muscle weakness or cardiac involvement. DNAJB6 is a highly conserved member of the Jproteins, also known as the heat shock protein (Hsp) 40 family, and consists of an N-terminal J domain and a C-terminal domain linked by the G/F D domain enriched in glycine and phenylalanine.2,3,5 Four pathogenic mutations have been identified so far in DNAJB6, p.Phe89Ile, p.Phe93Leu, p.Phe96Leu, and p.Phe96Ile, all occurring in the G/F domain.2,3,9 Here, we describe the clinical, electromyographic, pathological, and molecular findings in a patient with DNAJB6 myopathy due to p.Phe89Ile, affecting 4 generations of a family. CASE REPORT
A 56-year-old woman had difficulty running and keeping up with her peers when she was about 8 years of age. She was a slow runner, and could not participate in gym class due to weakness and “lack of coordination.” Around age 20 she noted slowly progressive proximal lower extremity weakness, which 15 years later extended to the proximal upper extremity muscles. She developed muscle atrophy in her legs, which had previously been described as “very muscular.” Additional symptoms included muscle stiffness that improved with activity, muscle cramps independent from activity, and dysphagia, for which she had undergone esophageal stretching multiple times. She had past history of unilateral lattice retinal degeneration. Several family members in 4 generations were affected by proximal muscle weakness MUSCLE & NERVE
April 2014
607
fibers, small globular congophilic deposits in most vacuoles, 2 or 3 cytochrome c oxidase–negative fibers per fascicle, and mild type 1 fiber predominance (Fig. 2). No necrotic or regenerating muscle fibers or inflammatory cells were present. Sequencing of DNAJB6 detected a known pathogenic heterozygous mutation c.265T>A (p.Phe89Ile). Sequencing of valosin-containing protein (VCP) and myosin heavy chain type 2 (MYH2) genes, which are known causes for autosomal dominant vacuolar myopathy, revealed no mutations. FIGURE 1. Pedigree of the DNAJB6 myopathy family. Affected subjects are marked in black. Arrow: proband; filled circle: early death; ?: lack of medical information.
(Fig. 1). In addition to the proband, a sister (III:6) and 2 other individuals (V:1 and V:3) became symptomatic in childhood with leg weakness and difficulty climbing stairs. All other affected family members had disease onset in adulthood. Subject III:3 was the most severely affected and became wheelchair-bound at age 50 and died at age 70. The proband’s father and his brother (II:1) remained ambulatory until death at age 62 of malignancy and approximately age 50 of unknown cause, respectively. The oldest living family member (III:4) is ambulatory at age 65. The paternal side of the family is of Native American and Scottish descent. The patient’s neurological examination revealed symmetric proximal muscle weakness, which was mild in the supraspinatus, infraspinatus, pectoral muscles, and hamstrings (MRC 4) and moderate in the iliopsoas, gluteus medius, and gluteus maximus (MRC 3.5), resulting in a waddling gait. She was unable to arise from supine to sitting unless she first rolled on her side. Strength in other muscles was preserved, including quadriceps and thigh adductors. The calf muscles were mildly atrophic, despite her ability to walk on toes. She had no action or percussion myotonia; the rest of the examination was normal. Serum creatine kinase (CK) values were normal, as were calcium and alkaline phosphatase. Electromyographic (EMG) study demonstrated small and polyphasic motor unit potentials, early recruitment, and few fibrillation potentials in proximal muscles; motor and sensory nerve conduction studies were normal. Video-fluoroscopic swallowing study, spirometry, electrocardiogram, and dobutamine stress echocardiogram findings were normal. Biopsy of the left gluteus medius showed muscle fiber size variability, numerous muscle fibers harboring vacuoles, most of which were lined by membranous material and were overreactive for acid phosphatase, focal irregular loss of oxidative enzyme reactivity in some vacuolated 608
Limb-Girdle Muscular Dystrophy 1E
DISCUSSION
We describe a patient from a 4-generation family affected by DNAJB6 myopathy, which became symptomatic in childhood with a limb-girdle phenotype and harboring a known pathogenic mutation, p.Phe89Ile. The patient described and the family member phenotypes share similarities but also differences from the cases reported so far. There was variability in age of disease onset, and 4 family members became symptomatic in childhood, suggesting that childhood onset of the myopathy, described previously in a single patient,9 is not rare. The 56-year-old proband, who also manifested in childhood, had very selective proximal muscle weakness that spared quadriceps and thigh adductors, muscles that have been described to be weak and radiologically involved early in previous reports of DNAJB6 myopathy.5,6,10 Our patient did not have a muscle MRI study, and therefore we cannot exclude subclinical involvement of thigh adductors and quadriceps, but the normal strength and size of these muscles 5 decades after onset of weakness would point away from significant fatty replacement. The patient had also abdominal wall muscle weakness, as suggested by her inability to arise from supine to sitting, an observation not reported previously in other DNAJB6 myopathy individuals. She had normal CK values, as observed previously in DNAJB6 myopathy, although more commonly there is a 2–5-fold increase in CK levels.3,5,6 The numerous rimmed vacuoles and associated congophilic inclusions were the dominant pathological features of her muscle biopsy. Rimmed vacuoles are a pathological feature of DNAJB6 myopathy, and intravacuolar filamentous inclusions have been detected by electron microscopy in some patients.5 However, the patient’s muscle biopsy displayed numerous intracellular congophilic inclusions that were easily detectable in Congo red–stained sections viewed under rhodamine optics (Fig. 2) and this, to our knowledge, is a novel finding. Trichrome-stained sections did not reveal dark cytoplasmic inclusions (Fig. 2B), which have been observed in other individuals with the MUSCLE & NERVE
April 2014
FIGURE 2. Muscle biopsy of the gluteus medius. (A, hematoxylin-eosin, and B, trichrome) Numerous rimmed vacuoles were present, as shown by arrows. No eosinophilic inclusions were present in trichrome-stained sections (B). (C) Over-reactivity for acid phosphatase. (D) Few muscle fibers showed focal loss of NADH reactivity. (E and F) Congophilic deposits were present within several vacuoles in Congo red-stained sections viewed under rhodamine optics. Bar 5 50.0 lm.
same myopathy.5,6,9 Her clinical, serological, and pathological features overlapped with other myopathies, such as VCP myopathy, which may also present with isolated limb-girdle weakness, rimmed vacuoles, and congophilic inclusions.11,12 Therefore, molecular analysis is the only tool that can provide a definite diagnosis. The observation of congophilic inclusions in this patient is of particular interest in light of the recently reported ability of the DNAJB6 protein to suppress the tendency of the polyglutamine peptides to form amyloid fibrils.13 DNAJB6, similar to other DNAJ family members, is a molecular chaperone of heat shock protein 70 (Hsp70); chaperones and co-chaperones protect proteins from irreversible aggregation during synthesis or at the time of cellular stress.14 On the basis of these observations, it could be speculated that the congophilic inclusions may be the result of protein aggregation secLimb-Girdle Muscular Dystrophy 1E
ondary to DNAJB6 protein loss of function, but further functional studies are needed to fully understand the pathogenesis of the disease. REFERENCES 1. Mitsuhashi S, Kang PB. Update on the genetics of limb girdle muscular dystrophy. Semin Pediatr Neurol 2012;19:211–218. 2. Sarparanta J, Jonson PH, Golzio C, Sandell S, Luque H, Screen M, et al. Mutations affecting the cytoplasmic functions of the cochaperone DNAJB6 cause limb-girdle muscular dystrophy. Nature Genet 2012;44:450–455, s451–452. 3. Harms MB, Sommerville RB, Allred P, Bell S, Ma D, Cooper P, et al. Exome sequencing reveals DNAJB6 mutations in dominantlyinherited myopathy. Ann Neurol 2012;71:407–416. 4. Speer MC, Vance JM, Grubber JM, Lennon Graham F, Stajich JM, Viles KD, et al. Identification of a new autosomal dominant limbgirdle muscular dystrophy locus on chromosome 7. Am J Hum Genet 1999;64:556–562. 5. Sandell S, Huovinen S, Sarparanta J, Luque H, Raheem O, Haapasalo H, et al. The enigma of 7q36 linked autosomal dominant limb girdle muscular dystrophy. J Neurol Neurosurg Psychiatry 2010; 81:834–839. 6. Hackman P, Sandell S, Sarparanta J, Luque H, Huovinen S, Palmio J, et al. Four new Finnish families with LGMD1D; refinement of the clinical phenotype and the linked 7q36 locus. Neuromuscul Disord 2011;21:338–344.
MUSCLE & NERVE
April 2014
609
7. Bushby KM, Beckmann JS. The 105th ENMC sponsored workshop: pathogenesis in the non-sarcoglycan limb-girdle muscular dystrophies, Naarden, April 12–14, 2002. Neuromuscul Disord 2003;13:80–90. 8. Greenberg SA, Salajegheh M, Judge DP, Feldman MW, Kuncl RW, Waldon Z, et al. Etiology of limb girdle muscular dystrophy 1D/1E determined by laser capture microdissection proteomics. Ann Neurol 2012;71:141–145. 9. Sato T, Hayashi YK, Oya Y, Kondo T, Sugie K, Kaneda D, et al. DNAJB6 myopathy in an Asian cohort and cytoplasmic/nuclear inclusions. Neuromuscul Disord 2013;23:269–276. 10. Sandell SM, Mahjneh I, Palmio J, Tasca G, Ricci E, Udd BA. ’Pathognomonic’ muscle imaging findings in DNAJB6 mutated LGMD1D. Eur J Neurol 2013 Jul 19. [Epub ahead of print] 11. Stojkovic T, el Hammouda H, Richard P, Lopez de Munain A, Ruiz-Martinez J, Camano P, et al. Clinical outcome in 19 French and
Spanish patients with valosin-containing protein myopathy associated with Paget’s disease of bone and frontotemporal dementia. Neuromuscul Dis 2009;19:316–323. 12. Kimonis V, Donkervoort S, Watts G. Inclusion body myopathy with Paget disease of bone and/or frontotemporal dementia. In: Pagon RA, Adam MP, Bird TD, editors. GeneReviews. Seattle, WA: University of Washington; 1993. 13. Ma˚nsson C, Kakkar V, Monsellier E, Sourigues Y, Harmark J, Kampinga HH, et al. DNAJB6 is a peptide-binding chaperone which can suppress amyloid fibrillation of polyglutamine peptides at substoichiometric molar ratios. Cell Stress Chaperones 2013 Aug 1. [Epub ahead of print] 14. Kampinga HH, Craig EA. The HSP70 chaperone machinery: J proteins as drivers of functional specificity. Nature Rev Mol Cell Biol 2010;11:579–592.
ENTECAVIR-ASSOCIATED MYOPATHY: A CASE REPORT AND LITERATURE REVIEW KAI YUAN, MD,1 GUOCHUN WANG, MD, PhD,1 ZHENGUO HUANG, MD,2 BING LIN, MD,1 HUIQIONG ZHOU, MD, PhD,1 and XIN LU, MD1 1 2
Department of Rheumatology, China–Japan Friendship Hospital, Yinghua East Road, Chaoyang District, Beijing 100029, China Department of Radiology, China–Japan Friendship Hospital, Beijing, China
Accepted 6 November 2013 ABSTRACT: Introduction: Entecavir, a nucleoside analog (NA), is effective for treatment of chronic hepatitis B virus (HBV) infection. Methods: We report the case of a patient we encountered with entecavir-associated myopathy. We also performed a literature review of myopathies associated with nucleoside analogs. Results: A 44-year-old man presented with a 3-month history of myalgia and progressive weakness. He had HBV infection and had received entecavir antiviral treatment for 5 years. Laboratory tests showed that serum creatine kinase levels were significantly elevated. Muscle histopathology showed abundant T-lymphocyte infiltration of muscle fibers, and HBV surface antigen and HBV core antigen were not present in muscle fibers. Entecavir-associated myopathy was subsequently diagnosed. The patient’s symptoms eventually resolved, and serum CK levels decreased rapidly after he stopped receiving entecavir treatments. Conclusions: Patients who receive NA therapy should be closely monitored for myopathic side effects. Muscle Nerve 49:610–614, 2014
Chronic infection by hepatitis B virus (HBV) affects more than 350 million people worldwide and can have serious consequences, including cirrhosis, hepatic failure, and hepatocellular carcinoma.1 Nucleoside analogs (NAs) and interferons are the first-line treatments for HBV. NAs include entecavir, Additional Supporting Information may be found in the online version of this article. This work was supported by the Beijing Science and Technology Committee (Z111107058811084). Abbreviations: ALT, alanine aminotransferase; AST, aspartate aminotransferase; ATP, adenosine triphosphate; CK, creatine kinase; HBV, hepatitis B virus; MANA, myopathies associated with nucleoside analogs; MHC, major histocompatibility complex; MMT, manual muscle testing; MRC, Medical Research Council; MRI, magnetic resonance imaging; NA, nucleoside analog; PM, polymyositis; STIR, short time inversion recovery Key words: creatine kinase; entecavir; hepatitis B; myopathy; nucleoside analog Correspondence to: X. Lu; e-mail: [email protected] C 2013 Wiley Periodicals, Inc. V
Published online 12 November 2013 in Wiley Online Library (wileyonlinelibrary. com). DOI 10.1002/mus.24118
610
Entecavir-Associated Myopathy
lamivudine, telbivudine, clevudine, and adefovir. The primary mechanism by which NAs act is to inhibit viral polymerase activity. Entecavir has proven to be effective and safe for HBV treatment, but the treatment has some side effects. Common adverse effects related to entecavir include headache, upper respiratory tract infection, upper abdominal pain, and flu-like symptoms. Most of these adverse effects are of mild-to-moderate severity.2 To our knowledge, entecavir-associated myopathy has not been reported. We describe a patient with entecavirassociated myopathy. We also review the literature regarding myopathies associated with nucleoside analogs (MANA) to find new information about their clinical and pathologic features, management, and prognosis. CASE REPORT
A 44-year-old man who had received entacavir therapy previously for chronic hepatitis B presented with a 3-month history of muscle pain and weakness in his lower extremities. He had a 20-year history of chronic hepatitis B infection and had been treated with entecavir for the HBV infection for the past 5 years on a stable dose of 0.5 mg/ day. He did not supplement the entecavir therapy with any other medication, and his blood HBV DNA levels had remained within the normal range (
