Pediatr Radiol DOI 10.1007/s00247-014-2979-z
CASE REPORT
Shrinking lung syndrome complicating pediatric systemic lupus erythematosus Natalie S. Burns & Anne M. Stevens & Ramesh S. Iyer
Received: 6 December 2013 / Revised: 23 February 2014 / Accepted: 17 March 2014 # Springer-Verlag Berlin Heidelberg 2014
Abstract Systemic lupus erythematosis (SLE) can affect the lungs and pleura, usually manifesting with pleural effusions or diffuse parenchymal disease. A rare manifestation of SLE is shrinking lung syndrome, a severe restrictive respiratory disorder. While pleuropulmonary complications of pediatric SLE are common, shrinking lung syndrome is exceedingly rare in children. We present a case of a 13-year-old girl previously diagnosed with lupus, who developed severe dyspnea on exertion and restrictive pulmonary physiology. Her chest radiographs on presentation demonstrated low lung volumes, and CT showed neither pleural nor parenchymal disease. Fluoroscopy demonstrated poor diaphragmatic excursion. While shrinking lung syndrome is described and studied in adults, there is only sparse reference to shrinking lung syndrome in children.
Keywords Systemic lupus erythematosis . Shrinking lung syndrome . Child . Radiography . Computed tomography
N. S. Burns Department of Radiology, University of Washington Medical Center, Seattle, WA, USA A. M. Stevens Division of Rheumatology, Department of Pediatrics, Seattle Children’s Hospital, Seattle, WA, USA R. S. Iyer (*) Department of Radiology, University of Washington School of Medicine, Seattle Children’s Hospital, 4800 Sand Point Way NE, Seattle, WA 98105, USA e-mail: [email protected]
Introduction Of all connective tissue disorders, systemic lupus erythematosus (SLE) has the highest rate of pleuropulmonary involvement. Shrinking lung syndrome is a rare manifestation of SLE, leading to severe restrictive physiology, significant morbidity and, rarely, death. Although the etiology remains unknown, dysfunctional muscles of respiration, particularly the diaphragm, are thought to be responsible. In sharp contrast to the severe clinical manifestations, the radiographic findings of shrinking lung disease are notably few, distinguishing it from SLE-related interstitial lung disease, which is the main alternative consideration. Chest radiographs characteristically show small lung volumes with or without pleural effusion but no parenchymal disease. High-resolution CT is frequently performed to detect underlying interstitial lung disease, which is absent in these patients. Finally, fluoroscopy and US may be performed to demonstrate diaphragmatic hypomotility and support the diagnosis of shrinking lung syndrome. We present an index case to illustrate how radiologists can assist our rheumatology and pulmonology colleagues in distinguishing shrinking lung syndrome from pulmonary fibrosis in cases of restrictive pulmonary symptomatology in children.
Case report An 11-year-old girl was diagnosed with systemic lupus erythematosus when she presented with 2 months of generalized malaise, migratory arthralgias, swelling of bilateral ankles, knees and wrists, morning stiffness, daily fevers and alopecia. Further work-up with laboratory panels revealed lymphopenia, C-reactive protein (CRP) elevation, a positive anti-nuclear antibody (ANA) test (titer of 1:5,120), and several other autoantibodies including anti-dsDNA, anti-Smith, anti-SSA
Pediatr Radiol
was treated with rituximab, to which she responded very well clinically. Her most recent PFTs at 17 years of age demonstrated substantial increases in her FVC and TLC at 82% and 80%, respectively (Fig. 4).
Discussion
and anti-phospholipid antibodies. She was initially treated with prednisone, azathoprine and hydroxychloroquine. At the age of 13, she began experiencing dyspnea on exertion and chest pain, with clear lungs on auscultation. Pulmonary function tests (PFTs) demonstrated a restrictive pattern. By the age of 14, her symptoms had progressed and she was ultimately hospitalized. Her pulmonary function tests demonstrated a forced vital capacity (FVC) of 31% predicted, total lung capacity (TLC) of 32% and DLCO (diffusing capacity of the lung for carbon monoxide) corrected for lung volumes of 96%. Chest radiography was remarkable only for low lung volumes and a left pleural effusion (Fig. 1). CT demonstrated low lung volumes with mild bibasilar atelectasis, small bilateral pleural effusions and a small pericardial effusion (Fig. 2). There was no evidence of interstitial lung disease or other parenchymal process. Monthly cyclophosphamide was started, which led to a fluctuating clinical course, despite improved PFTs, with a subsequent hospital admission nearly 1 year later. A fluoroscopic study of the diaphragm demonstrated symmetrical poor excursion bilaterally (Fig. 3). She
SLE is a multisystem autoimmune disorder, which can occur at any age, from early childhood to late adult years [1]. Approximately 20–25% of SLE cases are diagnosed in children, with the yearly incidence of pediatric SLE ranging from 0.36 to 0.9 per 100,000, in contrast to an incidence of 3.0 per 100,000 in adults. The peak incidence of pediatric SLE onset is 11.06 years, similar to that of our patient. There is a strong female predominance; however, the male to female ratio is greater in the younger pediatric SLE population, compared with adolescents and adults. The symptoms can vary, but among the most common are fever, rash and arthritis [1]. Pleuropulmonary complications are common in both pediatric and adult populations, occurring in 57% of pediatric patients and 60–80% of adult patients, higher than any other collagen vascular disease [2, 3]. The pleurae are the most common site of thoracic involvement, with clinical pleurisy in 40% of pediatric patients, and evident pleural effusions in up to half of those patients. The most common pulmonary complication in pediatric SLE is infection, and other less common manifestations include lupus pneumonitis, pulmonary hemorrhage and interstitial lung disease (14%, 10% and 4%, respectively) and pulmonary hypertension in 4–8% [3]. Shrinking lung syndrome is a rare pulmonary complication of SLE, with an incidence of less than 1% in SLE patients, and is thought to be even more rare in pediatric SLE [2, 4]. When shrinking lung syndrome was first described, the pathophysiology was postulated to be secondary to surfactant deficiency, leading to increased alveolar surface tension and microatelectasis [2, 4]. The focus shifted when differences in transdiaphragmatic pressures were found, suggestive of
Fig. 2 High-resolution CT. a Absence of parenchymal or interstitial lung disease is noted on a representative image at the level of the pulmonary arterial bifurcation. b The patient did have small bilateral pleural effusions
(arrows) and a small pericardial effusion (arrowhead), which are common in SLE and were not attributed to her severe restrictive pulmonary physiology
Fig. 1 Posteroanterior chest radiograph of a 14-year-old girl with shrinking lung syndrome complicating her systemic lupus erythematosus shows low lung volumes and a small left pleural effusion
Pediatr Radiol
Fig. 3 Diaphragmatic fluoroscopy during forceful expiration (a) and inspiration (b) demonstrates 0.5-cm orthograde excursion of the diaphragm during the respiratory cycle, corresponding to approximately ¼ of a rib interspace in this patient. The arrows indicate the dome of the
right diaphragm; however, bilateral hypomotility was observed. Findings are consistent with symmetrical diaphragmatic weakness. The cassette grid used for the examination has line markers spaced at 1-cm intervals
diaphragmatic pathology [4, 5]. Decreased diaphragmatic excursion and decreased maximal inspiratory pressures (MIP) found in these patients are supportive of a diaphragmatic etiology [4, 5]. Various possible mechanisms, including pleural adhesions from recurrent inflammation, phrenic nerve dysfunction and diaphragmatic fibrosis, have all been studied but have thus far yielded conflicting results. The exact cause remains unclear and may be multifactorial [2, 4, 5].
Patients with shrinking lung syndrome typically present with pleuritic chest pain and dyspnea on exertion, as was the case with the presented patient [2, 4]. Dry cough and fever are rare and may assist in distinguishing this entity from pulmonary infection, a more common complication in SLE [4]. While our patient was diagnosed with shrinking lung syndrome approximately 2.3 years following her diagnosis of SLE, shrinking lung syndrome can occur at any time in the disease course, with the reported mean time of onset of approximately 4.3 years in the general shrinking lung syndrome population [4]. Pulmonary function tests demonstrate a marked restrictive physiology, with decreased forced expiratory volume (FEV) and TLC. The DLCO may concurrently be reduced, but when corrected for low lung volumes, is often normal, which is a major differentiating factor between shrinking lung syndrome and interstitial lung disease. The normal corrected DLCO in shrinking lung syndrome suggests that the alveolar membrane is spared, and therefore the pathophysiology is more likely related to the low lung volumes. In contrast, interstitial lung disease leads to reduction in all three PFT measures - FEV1, TLC and DLCO [2, 4]. Radiographic findings in SLE most commonly include pleural or pericardial effusions as well as diffuse parenchymal abnormalities in the context of alveolar hemorrhage, SLE pneumonitis or interstitial lung disease [2, 5]. Unlike the above pulmonary manifestations, there are relatively minimal radiographic findings in shrinking lung syndrome. Chest radiographs most frequently are normal or demonstrate low lung volumes with elevation of the hemidiaphragms, in spite of maximal inspirational efforts [2, 4]. There may occasionally be small pleural effusions or mild pleural thickening [2]. High-resolution CT may be obtained to evaluate for early or subtle evidence of diffuse parenchymal involvement. But in patients with shrinking lung syndrome who undergo these studies the lungs will be clear save for atelectasis [2, 5]. Specifically, there is no evidence of interstitial lung disease
Fig. 4 Pulmonary function tests (PFTs) over time in this patient with systemic lupus erythematosis (SLE). The diagnosis of shrinking lung syndrome (SLS) was made following a year-long decline in PFTs. The patient’s PFTs improved substantially following the initiation of immunomodulatory therapy, particularly rituximab
Pediatr Radiol
as a cause of restrictive lung process. While small pleural effusions and mild pleural thickening may be identified, as on radiography, extensive pleural disease is not present [2, 5]. Fluoroscopy can provide value in these cases to evaluate diaphragmatic excursion. Typically patients are asked to perform provocative maneuvers such as a sniff test. A spectrum of reduced diaphragmatic excursion (less than one interspace inferiorly with inspiration) to paradoxical movement may be noted in shrinking lung syndrome. To distinguish between weakness and paralysis, the diaphragm is observed in quiet and deep respiration. The presence of some orthotopic motion indicates weakness, while complete absence of orthotopic motion indicates paralysis, and is a rare finding [2, 5, 6]. Another modality that is useful in the evaluation of diaphragmatic function is US, given its lack of ionizing radiation, portability and ease of performance. M-mode sonography can quantitate diaphragmatic excursion. This measurement is not only helpful for diagnosis but can also be used for follow-up. There should normally be less than 50% difference in excursion between both hemidiaphragms. [7]. The primary diagnostic consideration in pediatric patients with SLE and restrictive pulmonary function is interstitial lung disease. HRCT is substantially more sensitive than chest radiographs for this diagnosis, rendering a normal chest radiograph in the setting of dyspnea on exertion insufficient for excluding either interstitial lung disease or shrinking lung syndrome, or differentiating between these conditions. In patients with interstitial lung disease secondary to SLE, HRCT may demonstrate interlobular septal thickening, reticular linear hyperattenuation, ground-glass opacities and parenchymal architectural distortion. Honeycombing is rarely found [8]. The exclusion of these findings by CT strongly suggests shrinking lung syndrome as cause for restrictive lung physiology. The treatment for shrinking lung syndrome includes anti-inflammatory and immunosuppressive agents. Theophylline and albuterol have also been used with success to improve diaphragmatic function [4]. The overall prognosis for some patients with SLE-related shrinking lung syndrome is favorable, with many patients reporting subjective improvement in symptoms [4]. Symptoms usually improve in weeks to months of therapy initiation, but symptom resolution has been reported to take up to 4 years in adults [2, 4]. If the patient fails to clinically improve, their pulmonary function typically remains stable. Progression occurs in the minority (2%), with rare cases of death [4]. In most cases, the clinical history, combined with pulmonary function tests, is sufficient for the diagnosis of shrinking lung syndrome. Our patient demonstrated many typical features for this condition, including female gender, early adolescence, and the onset of chest pain and dyspnea a few years
after her diagnosis of SLE. Her PFTs showed a characteristic restrictive physiology yet normal DLCO, reducing the likelihood of interstitial lung disease, which was the main diagnostic consideration. Her imaging was relatively normal, demonstrating only low lung volumes and a pleural effusion, and, importantly, no evidence of interstitial lung disease. A fluoroscopy study confirmed the diagnosis by demonstrating reduced diaphragmatic excursion, and she improved remarkably on immunomodulatory therapy. Her restrictive physiology, in combination with normal DLCO and relatively normal imaging, strongly suggested the diagnosis. This process underscores the importance of interdisciplinary collaboration between the radiologist and the clinicians. In summary, when presented with a pediatric patient with SLE and restrictive pulmonary physiology, shrinking lung syndrome is an important entity of which to be aware. Although rare, knowledge of shrinking lung syndrome has important implications in the treatment and prognosis of the patient, and thus distinguishing this entity from interstitial lung disease is crucial. An important clue to this distinction and the correct diagnosis of shrinking lung syndrome is the presence of a normal DLCO in a patient with restrictive physiology. The radiologist can provide further value by alerting the referring rheumatologist or pulmonologist of this diagnostic consideration in the context of relatively normal imaging studies; namely, a chest radiograph that demonstrates only low lung volumes, possibly with a pleural effusion, and a normal or near-normal CT chest, in a patient with severe restrictive pulmonary function. The absence of diffuse parenchymal abnormalities on CT will exclude interstitial lung disease. Fluoroscopy and US may be performed to support a diagnosis of shrinking lung syndrome and may show poor diaphragmatic excursion. Ultrasound can also be considered as a way to monitor patient response to therapy. The clinician may then employ the proper immunomodulatory therapy and offer the patient a favorable outcome.
Conflicts of interest None.
References 1. Zhu J, Wu F, Huang X (2013) Age-related differences in the clinical characteristics of systemic lupus erythematosus in children. Rheumatol Int 33:111–115 2. Karim MY, Miranda LC, Tench CM et al (2002) Presentation and prognosis of the shrinking lung syndrome in systemic lupus erythematosus. Semin Arthritis Rheum 31:289–298 3. Papadimitraki ED, Isenberg DA (2009) Childhood- and adult-onset lupus: an update of similarities and differences. Expert Rev Clin Immunol 5:391–403 4. Toya SP, Tzelepis GE (2009) Association of the shrinking lung syndrome in systemic lupus erythematosus with pleurisy: a systematic review. Semin Arthritis Rheum 39:30–37
Pediatr Radiol 5. Warrington KJ, Moder KG, Brutinel WM (2000) The shrinking lungs syndrome in systemic lupus erythematosus. Mayo Clin Proc 75:467– 472 6. Nason LK, Walker CM, McNeeley MF et al (2012) Imaging of the diaphragm: anatomy and function. Radiographics 32:E51– E70
7. Chavhan GB, Babyn PS, Cohen RA et al (2010) Multimodality imaging of the pediatric diaphragm: anatomy and pathologic conditions. Radiographics 30:1797–1817 8. Kim EA, Lee KS, Johkoh T et al (2002) Interstitial lung diseases associated with collagen vascular diseases: radiologic and histopathologic findings. Radiographics 22:S151–S165
CASE REPORT
Shrinking lung syndrome complicating pediatric systemic lupus erythematosus Natalie S. Burns & Anne M. Stevens & Ramesh S. Iyer
Received: 6 December 2013 / Revised: 23 February 2014 / Accepted: 17 March 2014 # Springer-Verlag Berlin Heidelberg 2014
Abstract Systemic lupus erythematosis (SLE) can affect the lungs and pleura, usually manifesting with pleural effusions or diffuse parenchymal disease. A rare manifestation of SLE is shrinking lung syndrome, a severe restrictive respiratory disorder. While pleuropulmonary complications of pediatric SLE are common, shrinking lung syndrome is exceedingly rare in children. We present a case of a 13-year-old girl previously diagnosed with lupus, who developed severe dyspnea on exertion and restrictive pulmonary physiology. Her chest radiographs on presentation demonstrated low lung volumes, and CT showed neither pleural nor parenchymal disease. Fluoroscopy demonstrated poor diaphragmatic excursion. While shrinking lung syndrome is described and studied in adults, there is only sparse reference to shrinking lung syndrome in children.
Keywords Systemic lupus erythematosis . Shrinking lung syndrome . Child . Radiography . Computed tomography
N. S. Burns Department of Radiology, University of Washington Medical Center, Seattle, WA, USA A. M. Stevens Division of Rheumatology, Department of Pediatrics, Seattle Children’s Hospital, Seattle, WA, USA R. S. Iyer (*) Department of Radiology, University of Washington School of Medicine, Seattle Children’s Hospital, 4800 Sand Point Way NE, Seattle, WA 98105, USA e-mail: [email protected]
Introduction Of all connective tissue disorders, systemic lupus erythematosus (SLE) has the highest rate of pleuropulmonary involvement. Shrinking lung syndrome is a rare manifestation of SLE, leading to severe restrictive physiology, significant morbidity and, rarely, death. Although the etiology remains unknown, dysfunctional muscles of respiration, particularly the diaphragm, are thought to be responsible. In sharp contrast to the severe clinical manifestations, the radiographic findings of shrinking lung disease are notably few, distinguishing it from SLE-related interstitial lung disease, which is the main alternative consideration. Chest radiographs characteristically show small lung volumes with or without pleural effusion but no parenchymal disease. High-resolution CT is frequently performed to detect underlying interstitial lung disease, which is absent in these patients. Finally, fluoroscopy and US may be performed to demonstrate diaphragmatic hypomotility and support the diagnosis of shrinking lung syndrome. We present an index case to illustrate how radiologists can assist our rheumatology and pulmonology colleagues in distinguishing shrinking lung syndrome from pulmonary fibrosis in cases of restrictive pulmonary symptomatology in children.
Case report An 11-year-old girl was diagnosed with systemic lupus erythematosus when she presented with 2 months of generalized malaise, migratory arthralgias, swelling of bilateral ankles, knees and wrists, morning stiffness, daily fevers and alopecia. Further work-up with laboratory panels revealed lymphopenia, C-reactive protein (CRP) elevation, a positive anti-nuclear antibody (ANA) test (titer of 1:5,120), and several other autoantibodies including anti-dsDNA, anti-Smith, anti-SSA
Pediatr Radiol
was treated with rituximab, to which she responded very well clinically. Her most recent PFTs at 17 years of age demonstrated substantial increases in her FVC and TLC at 82% and 80%, respectively (Fig. 4).
Discussion
and anti-phospholipid antibodies. She was initially treated with prednisone, azathoprine and hydroxychloroquine. At the age of 13, she began experiencing dyspnea on exertion and chest pain, with clear lungs on auscultation. Pulmonary function tests (PFTs) demonstrated a restrictive pattern. By the age of 14, her symptoms had progressed and she was ultimately hospitalized. Her pulmonary function tests demonstrated a forced vital capacity (FVC) of 31% predicted, total lung capacity (TLC) of 32% and DLCO (diffusing capacity of the lung for carbon monoxide) corrected for lung volumes of 96%. Chest radiography was remarkable only for low lung volumes and a left pleural effusion (Fig. 1). CT demonstrated low lung volumes with mild bibasilar atelectasis, small bilateral pleural effusions and a small pericardial effusion (Fig. 2). There was no evidence of interstitial lung disease or other parenchymal process. Monthly cyclophosphamide was started, which led to a fluctuating clinical course, despite improved PFTs, with a subsequent hospital admission nearly 1 year later. A fluoroscopic study of the diaphragm demonstrated symmetrical poor excursion bilaterally (Fig. 3). She
SLE is a multisystem autoimmune disorder, which can occur at any age, from early childhood to late adult years [1]. Approximately 20–25% of SLE cases are diagnosed in children, with the yearly incidence of pediatric SLE ranging from 0.36 to 0.9 per 100,000, in contrast to an incidence of 3.0 per 100,000 in adults. The peak incidence of pediatric SLE onset is 11.06 years, similar to that of our patient. There is a strong female predominance; however, the male to female ratio is greater in the younger pediatric SLE population, compared with adolescents and adults. The symptoms can vary, but among the most common are fever, rash and arthritis [1]. Pleuropulmonary complications are common in both pediatric and adult populations, occurring in 57% of pediatric patients and 60–80% of adult patients, higher than any other collagen vascular disease [2, 3]. The pleurae are the most common site of thoracic involvement, with clinical pleurisy in 40% of pediatric patients, and evident pleural effusions in up to half of those patients. The most common pulmonary complication in pediatric SLE is infection, and other less common manifestations include lupus pneumonitis, pulmonary hemorrhage and interstitial lung disease (14%, 10% and 4%, respectively) and pulmonary hypertension in 4–8% [3]. Shrinking lung syndrome is a rare pulmonary complication of SLE, with an incidence of less than 1% in SLE patients, and is thought to be even more rare in pediatric SLE [2, 4]. When shrinking lung syndrome was first described, the pathophysiology was postulated to be secondary to surfactant deficiency, leading to increased alveolar surface tension and microatelectasis [2, 4]. The focus shifted when differences in transdiaphragmatic pressures were found, suggestive of
Fig. 2 High-resolution CT. a Absence of parenchymal or interstitial lung disease is noted on a representative image at the level of the pulmonary arterial bifurcation. b The patient did have small bilateral pleural effusions
(arrows) and a small pericardial effusion (arrowhead), which are common in SLE and were not attributed to her severe restrictive pulmonary physiology
Fig. 1 Posteroanterior chest radiograph of a 14-year-old girl with shrinking lung syndrome complicating her systemic lupus erythematosus shows low lung volumes and a small left pleural effusion
Pediatr Radiol
Fig. 3 Diaphragmatic fluoroscopy during forceful expiration (a) and inspiration (b) demonstrates 0.5-cm orthograde excursion of the diaphragm during the respiratory cycle, corresponding to approximately ¼ of a rib interspace in this patient. The arrows indicate the dome of the
right diaphragm; however, bilateral hypomotility was observed. Findings are consistent with symmetrical diaphragmatic weakness. The cassette grid used for the examination has line markers spaced at 1-cm intervals
diaphragmatic pathology [4, 5]. Decreased diaphragmatic excursion and decreased maximal inspiratory pressures (MIP) found in these patients are supportive of a diaphragmatic etiology [4, 5]. Various possible mechanisms, including pleural adhesions from recurrent inflammation, phrenic nerve dysfunction and diaphragmatic fibrosis, have all been studied but have thus far yielded conflicting results. The exact cause remains unclear and may be multifactorial [2, 4, 5].
Patients with shrinking lung syndrome typically present with pleuritic chest pain and dyspnea on exertion, as was the case with the presented patient [2, 4]. Dry cough and fever are rare and may assist in distinguishing this entity from pulmonary infection, a more common complication in SLE [4]. While our patient was diagnosed with shrinking lung syndrome approximately 2.3 years following her diagnosis of SLE, shrinking lung syndrome can occur at any time in the disease course, with the reported mean time of onset of approximately 4.3 years in the general shrinking lung syndrome population [4]. Pulmonary function tests demonstrate a marked restrictive physiology, with decreased forced expiratory volume (FEV) and TLC. The DLCO may concurrently be reduced, but when corrected for low lung volumes, is often normal, which is a major differentiating factor between shrinking lung syndrome and interstitial lung disease. The normal corrected DLCO in shrinking lung syndrome suggests that the alveolar membrane is spared, and therefore the pathophysiology is more likely related to the low lung volumes. In contrast, interstitial lung disease leads to reduction in all three PFT measures - FEV1, TLC and DLCO [2, 4]. Radiographic findings in SLE most commonly include pleural or pericardial effusions as well as diffuse parenchymal abnormalities in the context of alveolar hemorrhage, SLE pneumonitis or interstitial lung disease [2, 5]. Unlike the above pulmonary manifestations, there are relatively minimal radiographic findings in shrinking lung syndrome. Chest radiographs most frequently are normal or demonstrate low lung volumes with elevation of the hemidiaphragms, in spite of maximal inspirational efforts [2, 4]. There may occasionally be small pleural effusions or mild pleural thickening [2]. High-resolution CT may be obtained to evaluate for early or subtle evidence of diffuse parenchymal involvement. But in patients with shrinking lung syndrome who undergo these studies the lungs will be clear save for atelectasis [2, 5]. Specifically, there is no evidence of interstitial lung disease
Fig. 4 Pulmonary function tests (PFTs) over time in this patient with systemic lupus erythematosis (SLE). The diagnosis of shrinking lung syndrome (SLS) was made following a year-long decline in PFTs. The patient’s PFTs improved substantially following the initiation of immunomodulatory therapy, particularly rituximab
Pediatr Radiol
as a cause of restrictive lung process. While small pleural effusions and mild pleural thickening may be identified, as on radiography, extensive pleural disease is not present [2, 5]. Fluoroscopy can provide value in these cases to evaluate diaphragmatic excursion. Typically patients are asked to perform provocative maneuvers such as a sniff test. A spectrum of reduced diaphragmatic excursion (less than one interspace inferiorly with inspiration) to paradoxical movement may be noted in shrinking lung syndrome. To distinguish between weakness and paralysis, the diaphragm is observed in quiet and deep respiration. The presence of some orthotopic motion indicates weakness, while complete absence of orthotopic motion indicates paralysis, and is a rare finding [2, 5, 6]. Another modality that is useful in the evaluation of diaphragmatic function is US, given its lack of ionizing radiation, portability and ease of performance. M-mode sonography can quantitate diaphragmatic excursion. This measurement is not only helpful for diagnosis but can also be used for follow-up. There should normally be less than 50% difference in excursion between both hemidiaphragms. [7]. The primary diagnostic consideration in pediatric patients with SLE and restrictive pulmonary function is interstitial lung disease. HRCT is substantially more sensitive than chest radiographs for this diagnosis, rendering a normal chest radiograph in the setting of dyspnea on exertion insufficient for excluding either interstitial lung disease or shrinking lung syndrome, or differentiating between these conditions. In patients with interstitial lung disease secondary to SLE, HRCT may demonstrate interlobular septal thickening, reticular linear hyperattenuation, ground-glass opacities and parenchymal architectural distortion. Honeycombing is rarely found [8]. The exclusion of these findings by CT strongly suggests shrinking lung syndrome as cause for restrictive lung physiology. The treatment for shrinking lung syndrome includes anti-inflammatory and immunosuppressive agents. Theophylline and albuterol have also been used with success to improve diaphragmatic function [4]. The overall prognosis for some patients with SLE-related shrinking lung syndrome is favorable, with many patients reporting subjective improvement in symptoms [4]. Symptoms usually improve in weeks to months of therapy initiation, but symptom resolution has been reported to take up to 4 years in adults [2, 4]. If the patient fails to clinically improve, their pulmonary function typically remains stable. Progression occurs in the minority (2%), with rare cases of death [4]. In most cases, the clinical history, combined with pulmonary function tests, is sufficient for the diagnosis of shrinking lung syndrome. Our patient demonstrated many typical features for this condition, including female gender, early adolescence, and the onset of chest pain and dyspnea a few years
after her diagnosis of SLE. Her PFTs showed a characteristic restrictive physiology yet normal DLCO, reducing the likelihood of interstitial lung disease, which was the main diagnostic consideration. Her imaging was relatively normal, demonstrating only low lung volumes and a pleural effusion, and, importantly, no evidence of interstitial lung disease. A fluoroscopy study confirmed the diagnosis by demonstrating reduced diaphragmatic excursion, and she improved remarkably on immunomodulatory therapy. Her restrictive physiology, in combination with normal DLCO and relatively normal imaging, strongly suggested the diagnosis. This process underscores the importance of interdisciplinary collaboration between the radiologist and the clinicians. In summary, when presented with a pediatric patient with SLE and restrictive pulmonary physiology, shrinking lung syndrome is an important entity of which to be aware. Although rare, knowledge of shrinking lung syndrome has important implications in the treatment and prognosis of the patient, and thus distinguishing this entity from interstitial lung disease is crucial. An important clue to this distinction and the correct diagnosis of shrinking lung syndrome is the presence of a normal DLCO in a patient with restrictive physiology. The radiologist can provide further value by alerting the referring rheumatologist or pulmonologist of this diagnostic consideration in the context of relatively normal imaging studies; namely, a chest radiograph that demonstrates only low lung volumes, possibly with a pleural effusion, and a normal or near-normal CT chest, in a patient with severe restrictive pulmonary function. The absence of diffuse parenchymal abnormalities on CT will exclude interstitial lung disease. Fluoroscopy and US may be performed to support a diagnosis of shrinking lung syndrome and may show poor diaphragmatic excursion. Ultrasound can also be considered as a way to monitor patient response to therapy. The clinician may then employ the proper immunomodulatory therapy and offer the patient a favorable outcome.
Conflicts of interest None.
References 1. Zhu J, Wu F, Huang X (2013) Age-related differences in the clinical characteristics of systemic lupus erythematosus in children. Rheumatol Int 33:111–115 2. Karim MY, Miranda LC, Tench CM et al (2002) Presentation and prognosis of the shrinking lung syndrome in systemic lupus erythematosus. Semin Arthritis Rheum 31:289–298 3. Papadimitraki ED, Isenberg DA (2009) Childhood- and adult-onset lupus: an update of similarities and differences. Expert Rev Clin Immunol 5:391–403 4. Toya SP, Tzelepis GE (2009) Association of the shrinking lung syndrome in systemic lupus erythematosus with pleurisy: a systematic review. Semin Arthritis Rheum 39:30–37
Pediatr Radiol 5. Warrington KJ, Moder KG, Brutinel WM (2000) The shrinking lungs syndrome in systemic lupus erythematosus. Mayo Clin Proc 75:467– 472 6. Nason LK, Walker CM, McNeeley MF et al (2012) Imaging of the diaphragm: anatomy and function. Radiographics 32:E51– E70
7. Chavhan GB, Babyn PS, Cohen RA et al (2010) Multimodality imaging of the pediatric diaphragm: anatomy and pathologic conditions. Radiographics 30:1797–1817 8. Kim EA, Lee KS, Johkoh T et al (2002) Interstitial lung diseases associated with collagen vascular diseases: radiologic and histopathologic findings. Radiographics 22:S151–S165
