Pediatric Dermatology Vol. 31 No. 4 e96–e99, 2014
Extensive Nevus Comedonicus Involving the Palm: Questionable Role of the Pilosebaceous Unit in Pathogenesis Shikhar Ganjoo, M.D., Saritha Mohanan, M.D., S.M.V.M.C.H., Rashmi Kumari, M.D., Devinder M. Thappa, M.D., and Nachiappa G. Rajesh, M.D. Department of Skin and Sexually Transmitted Diseases, Jawaharlal Institute of Postgraduate Medical Education and Research, Puducherry, India
Abstract: A 10-year-old boy had multiple grouped pits with black plugs arranged along the lines of Blaschko on his left chest, arm, and palm. Involvement of the palms is rarely reported in the literature. Recent reports have described mosaic acneiform conditions that could share pathogenetic mechanisms with nevus comedonicus. We briefly review the literature on mosaic conditions with acneiform lesions including nevus comedonicus.
Nevus comedonicus is an uncommon skin abnormality ﬁrst described in 1895 by Kofmann, who used the term “comedo-nevus” to describe it (1). It comprises groups of pits ﬁlled with black keratinous plugs resembling blackheads that later can develop into inﬂammatory acne lesions (2). Nevus comedonicus may develop at any age, but is usually present at birth or develops before the age of 10 years. Men and women are equally aﬀected (2). A recent review discussed a few rare conditions with mosaic acneiform lesions, some of which may be related pathogenetically to tyrosine kinase receptor signalling pathways (3). We report a case of nevus comedonicus distributed over the left half of the body, including the palm, without any associated systemic abnormalities and brieﬂy review the recent literature on mosaic conditions with acneiform lesions and their pathogenesis.
CASE REPORT A 10-year-old boy, born of a third-degree consanguineous marriage, presented with congenital onset of multiple grouped pits ﬁlled with black plugs over the left side of the trunk, arm, and palm. Developmental milestones were normal. The parents reported that some of the aﬀected areas developed painful nodules that broke open with purulent discharge and resolved with atrophic scars after short courses of antibiotics. There was no history of any other treatments or procedures. There was no family history of similar disorders. Cutaneous examination revealed groups of dilated follicular openings ﬁlled with hard, black plugs distributed over the left arm and forearm, left side of the chest, and upper abdomen, all following the lines of Blaschko, with depressed atrophic scars in between
Address correspondence to Rashmi Kumari, M.D., Department of Skin and Sexually Transmitted Diseases, Jawaharlal Institute of Postgraduate Medical Education & Research, Puducherry 605009, India, or e-mail: [email protected]
© 2014 Wiley Periodicals, Inc.
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the lesions (Fig. 1A–C). The interfollicular skin was normal. The left palm showed pit-like lesions arranged in a linear pattern, with no keratin plugs or comedones. Examination did not reveal any abnormalities of the central nervous, skeletal, or ocular system. Routine hematologic investigations, including complete hemogram, biochemical parameters, liver function tests, and renal function tests, were within normal limits. Histopathologic examination of a papule with a keratotic plug taken from the chest showed a deep, wide invagination of acanthotic epidermis ﬁlled with concentric lamellae of keratin, consistent with the diagnosis of nevus comedonicus (Fig. 2). Histopathologic examination of the atrophic areas revealed only scar tissue. The patient was started on oral isotretinoin 0.5 mg/kg/day and oral doxycycline 100 mg twice a day (in view of nodulocystic and purulent lesions) for 2 months. At his next visit he reported fewer episodes of suppuration. He was asked to continue the same treatment until his next appointment 2 months later, but he was subsequently lost to follow-up. DISCUSSION Nevus comedonicus is rare. It can present as single or multiple lesions, unilaterally or bilaterally, and arranged in a linear, interrupted, dermatomal, Blaschkoid, or segmental pattern. The most common sites of distribution are the face, neck, trunk, and upper
arm. The palms, soles, and glans penis are occasionally involved (4,5). Clinically there are two types of nevus comedonicus (2). In the ﬁrst type, comedones are predominantly seen. In the second type, comedones undergo inﬂammatory changes, with late sequelae such as scars, keloids, ﬁstulas, and formation of follicular cysts. There have been reports of secondary infections in nevus comedonicus, as seen in our patient (6). Involvement of the palms is rarely reported in nevus comedonicus (5). Sebaceous glands are not normally found on the palms and soles (7). Therefore it is curious that our patient showed involvement of the palms, although clinical variability could explain this. Improper keratinization of the pilosebaceous unit is said to cause nevus comedonicus through various proposed mechanisms (2). Cytokeratin expression in nevus comedonicus is similar to that in normal skin (8), although a role for ﬁlaggrin in the disordered keratinization of nevus comedonicus has been postulated (8). Overstimulation of ﬁbroblast growth factor receptor 2 (FGFR-2) signalling with high expression of interleukin-1a may also be involved in the pathogenesis of nevus comedonicus (9). A role for csecretase found in hair follicle epithelium has also been postulated (9). The proposed pathogenetic mechanisms involving the pilosebaceous unit, including tyrosine kinase receptors or c-secretase, do not explain the palmar lesions, making ﬁlaggrin a likely candidate in the disordered keratinization of nevus comedonicus.
Figure 1. (A) Multiple comedones distributed in a linear fashion on the front of the chest and left arm in a 12-year-old boy. (B) Multiple comedones and atrophic scars present on the left arm. (C) Left palm showing pits arranged in a linear fashion.
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Figure 2. Histopathology showing dilated follicular ostia filled with keratin plugs (inset, top) and cystic invaginations lined by keratinizing squamous epithelium (inset, bottom) (hematoxylin and eosin, 409).
In view of the palmar involvement, we considered other rare conditions with similar morphology, such nevus trichilemmocysticus, Happle Tinschert syndrome (basaloid follicular hamartomas with comedo-like plugs), segmental acne, and mosaic Apert’s syndrome, as possible diﬀerential diagnoses (3). Characteristic histopathology discounted the ﬁrst two possibilities in our patient and onset at birth ruled out the third. We could not test for FGFR-2 mutations in our patient, but we considered mosaic Apert’s syndrome to be unlikely because of the absence of hypopigmentation and hypotrichosis. Nevus comedonicus syndrome is the association of nevus comedonicus with abnormalities of the central nervous system, skeletal system, skin, and eyes (9,10). Central nervous system involvement includes epilepsy, electroencephalogram abnormalities, and transverse myelitis. Skeletal system abnormalities include scoliosis, hemivertebrae, spina biﬁda occulta, foot deformities, absence of ﬁngers, syndactyly, and supernumerary digits. Cutaneous associations include ichthyosis, trichilemmal cysts, leukoderma, white hairs, Sturge–Weber syndrome, and hemangiomas. Ocular abnormalities include congenital cataracts, either unilateral or bilateral (10). Our patient did not have any systemic abnormalities, despite having extensive cutaneous involvement involving almost half of his trunk and one arm, similar to a systematized epidermal nevus.
Palmar involvement indicates that there is more to the pathogenesis of nevus comedonicus than disordered keratinization of the pilosebaceous unit. Further research on mosaic conditions with acneiform lesions is required to understand the multiple factors involved in comedogenesis; in turn this could help in the development of newer treatments for acne and related disorders. CONFLICT OF INTEREST None. REFERENCES 1. Kofmann S. Ein fall von seltener localisation und verbreitung von comedonen. Arch Dermatol Syph 1895;32:177–178. 2. Bhagwat PV, Tophakhane RS, Rathod RM et al. Nevus comedonicus along Blaschko’s lines. Indian J Dermatol Venereol Leprol 2009;75:330. 3. Torchia D, Schachner LA, Izakovic J. Segmental acne versus mosaic conditions with acne lesions. Dermatology 2012;224:10–14. 4. Moss C, Shahidullah H. Nevi and other developmental defects. In: Burns T, Breathnach SM, Cox N et al, eds. Rook’s textbook of dermatology, 8th ed. Oxford: Blackwell Science, 2010:18.11–18.13. 5. Harper KE, Spielvogel RL. Nevus comedonicus of the palm and wrist. Case report with review of ﬁve previously reported cases. J Am Acad Dermatol 1985; 12(1 Pt 2):185–188.
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6. Beck MH, Dave VK. Extensive nevus comedonicus. Arch Dermatol 1980;116:1048–1050. 7. Simpson NB, Cunliﬀe WJ. Disorders of sebaceous glands. In: Burns T, Breathnach S, Cox N et al, eds. Rook’s textbook of dermatology, 8th ed. Oxford: Blackwell, 2010:42.1–42.88. 8. Kurokawa I, Nakai Y, Nishimura K et al. Cytokeratin and ﬁlaggrin expression in nevus comedonicus. J Cutan Pathol 2007;34:338–341.
9. Tchernev G, Ananiev J, Semkova K et al. Nevus comedonicus: an updated review. Dermatol Ther (Heidelb) 2013;3:33–40. 10. Happle R. The group of epidermal nevus syndromes. Part I. Well deﬁned phenotypes. J Am Acad Dermatol 2010;63:1–22.