Are You Confident of the Diagnosis?
What you should be alert for in the history
About half of the cases are apparent at birth, with the remainder arising before puberty, especially in the first ten years of life. A very few sporadic cases have been reported in later years, usually following irritation or trauma at the affected site, thus representing Koebner’s isometric response in patients with prior nevus comedonicus elsewhere, or Wolf’s isotopic response in patients without prior history of nevus comedonicus. Prior lesions have included herpes zoster, lichen planus, vaccination, furunculosis, and physical trauma.
Characteristic findings on physical examination
Lesions usually appear on the face, neck, upper arms, chest, or abdomen as one or more groups of closely situated markedly dilated follicular ostia, each filled with a dark keratin plug. Lesions are characteristically arranged in bands or groups, and may be in a linear array along Blaschko’s lines. Sometimes, multiple linear lesions that terminate at the midlne may be seen. Most but not all cases are unilateral.
Lesions may be small, nevoid, or extensive. Some lesions may involve volar surfaces; when this happens eccrine sturctures may be seen to be involved clinically and histologically. Less common sites of involvement include scalp, and male and female genital mucus membranes.
Lesions range in size form 0.5 to 5mm in diameter and are closely grouped. Each lesion has the apperance of a darkly colored comedone (Figure 1). Some lesions may appear verrucous, especially over prominences such as elbows or knees. Secondary inflammation is often present, and may lead to cicatrix formation. Skin near lesions may appear hypopigmented. Lesions may worsen at puberty or during mensturation.
Nevus comedonicus may vary markedly in severity, promoting some authors to divide patients into two groups. The first has only comedo-like eruptions. The second has, in addition, large cysts and scarring from recurrent abscesses and fistula formation. In the first group, lesions are only of cosmetic concern, whereas in the second, scarring and suppuration are significant problems.
Expected results of diagnostic studies
On histology, there is an aggregation of dilated follicular infundibula with orthokeratotic plugging, absent or very rudimentary sebaceous elements, and the lack of normal hair follicles. The walls of the follicles are lined by several layers of keratinocytes, and are atrophic with sparse stratum granulosum. There may be epithelial budding out from the walls as well. Early lesions may show small hair shafts and small sebaceous glands. Eccrine and apocrine glands are usually normal on glabrous skin.
Differential diagnosis of nevus comedonicus includes other epidermal nevi, including especially nevus sebaceous of Jadassohn (typically located on the scalp, with three phases of evolution dependent on stage of differentiation of sebaceous gland), infantile acne, familial dyskeratotic comedones (widespread symmetrically distributed comedone-like hyperkeratotic papules, generally located on trunk, face, and arms), Favre-Racouchot disease (open and closed comedones located on actinically damaged skin), chloracne (aceniform eruption secondary to chemical exposure), Darier’s disease (skin-colored or yellow-brown papules with a greasy verrucous apperance, located in seborrheic regions and associated with nail and mucus membrane changes), and acne conglobata with extensive comedone formation (severe form of acne often resulting in disfigurement). Most can be excluded by skin biopsy.
Who is at Risk for Developing this Disease?
Nevus comedonicus is rare, accounting for only 1% of epidermal nevi. Only about 200 cases have been reported to date. In a retrospective examination of 417,511 pediatric patients in Mexico City, 443 patients were found to have epidermal nevi. Five of these patients were found to have nevus comedonicus. Males and females appear to be affected equally. There is no racial predisposition.
What is the Cause of the Disease?
Nevus comedonicus appears to be a subset of epidermal nevus. Somatic mutation has been proposed as the etiology of both. Some cases of familial lesions indicate more complex etiopathogenesis. Nevus comedonicus has been linked to a somatic mutation in fibroblast growth factor-2 receptor (FGFR-2). Several other diseases have been associated with this gene, including Apert’s syndrome, chondrodysplasia, and craniosynostosis syndromes.
Systemic Implications and Complications
Nevus comedonicus has been associated with a number of other entities. These are more likely in patients with widespread involvement. Some lesions are also associated with deeper anomalies in the same locations in muscle and bone.
When associated lesions are cancer, such as basal cell cancers, close monitoring of the patient is necessary to identify and treat any such malignancies. Malignant degeneration in lesions of nevus comedonicus itself has not been reported. Patients with any of these associations are sometimes referred to as having the “nevus comedonicus syndrome.” This syndrome should be considered in the context of epidermal nevus syndromes.
Reported asssociated entities include basal cell carcinomas and basal cell carcinoma syndromes, Sturge-Weber syndrome, vascular nevi, cataracts, interpapillary elastoma, absent finger and toes, pilar cysts, ecrine tumors including hidroadenoma, spiradenoma and syringocystadeoma papillariferum, hidradenoma papillariferum, Alagille’s syndrome, ichthyosis hysrtix, Becker’s nevus, deep pigmented hairs, skeletal defects, scoliosis, neurological defects, and spine and central nervous system anomalies.
Topical retinoid cream (tretinoin 0.1%),
Topical retinoid cream (0.1%) combined with topical corticosteroid ointment (mometasone furoate)
Topical 12% amonium lactate lotion
Optimal Therapeutic Approach for this Disease
The first step is to be certain of the diagnosis. No particular labarotory test is indicated, unless there is other involvement apparent or suspected based on clinical or other findings. Skin biopsy of the lesion should be done to confirm the diagnosis.
Localized lesions may be treated on a cosmetic basis, unless there are complications such as secondary infection. Spontaneous regression of the nevus comedonicus has not been reported. Treatment of associated lesions should be caried out as neeeded.
Topical retinoid cream (tretinoin 0.1%) has been reported to improve lesions. This agent acts by accelerating exfoliation of epithelium, resulting in expulsion of keratin plugs from comedonal lesions. It may be combined with topical corticosteroid ointment (mometasone furuate). Topical 12% amonium lactate lotion applied once daily has been reported to improve the comedone-like lesions. Topical tacalcitol has also been reported to be heplful. Topical tazarotene 0.05% cream has been combined with topical calcipotriene 0.005% cream with success.
More severe lesions with cystic disease may require systemic antibiotics (tetracycline 500mg orally twice daily or doxycycline 100mg orally twice daily) and intralesional steroids (IL kenalog 5-10mg/cc). A variable success rate with various antibiotic treatments have been reported.
Administration systemically of isoretinoin (0.5- 1.0mg/kg) has been reported to be effective in preventing cyst formation. The special restrictions on this drug because of its teratogenic and other side effects must be considered (iPledge regulations).
Surgical intervention may be required for larger lesions. Manual comedone extraction may help speed up the process.
Prognosis is excellent barring associated conditions (see unusual scenarios section) and with adequate local management.
Unusual Clinical Scenarios to Consider in Patient Management
One case report has been seen in a patient with nevus comedonicus complicated with lichen striatus and linear morphea.
A case has been reported in which hidradenitis suppurativa was seen possibly in association with nevus comedonicus.
What is the Evidence?
Solomon, LM, Esterly, NB. “Epidermal and other congenital organic nevi”. Curr Probl Pediatr. vol. 6. 1975. pp. 3-56. (This is an extremely comprehensive review of epidermal nevi by one of the giants in the field.)
Vidaurri-de La Cruz, H, Tamayo-Sanchez, L, Duran-McKinster, C. “Epidermal nevus syndromes: clinical findings in 35 patients”. Pediatr Dematol. vol. 21. 2004. pp. 432-439. (Of thirty-five patients with the epidermal nevus syndrome, three [8%] were found to have a nevus comedonicus.)
Wood, MG, Thew, MA. “Nevus comedonicus. A case with palmar involvement involvement and review of literature”. Arch Dermatol. vol. 98. 1968. pp. 111-6. (This is a case report of a palmar case, with an excellent review of the literature before 1968.)
Sinha, A, Natarajan, S. “Linear morphea, nevus comedonicus, and lichen striatus in a 5-year-old girl”. Pediatr Dermatol. vol. 28. 2011 Jan-Feb. pp. 72-4. (A case report noting overlapping disorders in conjuction with nevus comedonicus)
Dufour, DN, Bryld, LE, Jamec, GB. “Hidradenitis suppurativa complicating naevus comedonicus: the possible influence of mechanical stress on the development of hidradenitis suppurativa”. Dermatology. vol. 220. 2010. pp. 323-5. (An infant developed hidradenitis suppurativa in the inguinal region associated with nevus comedonicus)
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