Nevus Comedonicus

4/11/2009 · Kategori: Dermatology

Nevus Comedonicus

Author: Rossitza Lazova, MD, Associate Professor of Dermatology and Pathology, Director of Dermatopathology Residency and Fellowship Program, Yale University School of Medicine; Consulting Pathologist/Dermatopathologist, Veterans Affairs Medical Center, West Haven, Connecticut

Introduction

Background

In 1895, Kofmann¹ described the first case of nevus comedonicus (NC). It manifests as groups of closely set, dilated follicular openings with dark keratin plugs resembling comedones. The majority of cases are isolated. However, NC may be part of NC syndrome in association with skeletal or central nervous system anomalies, ocular abnormalities, and cutaneous defects. 

Pathophysiology

Many consider NC to be a hamartoma deriving from a failure of the mesodermal part of the folliculosebaceous unit to develop properly, with subsequent abnormal differentiation of the epithelial portion. The follicular structures that result are unable to form terminal hair or sebaceous glands and are capable only of producing soft keratin, which accumulates in the adnexal orifices and produces the comedonelike lesions observed in persons with this condition. Another view is that NC is an epidermal nevus involving hair follicles or an appendageal nevus of sweat ducts. Lesions that extend onto a palm or sole typically demonstrate sweat duct dilatation with keratin in the volar portion of the lesion. See Epidermal Nevus Syndrome for more information.

The etiology of NC is unclear. Why some NC patients present late in life is not known, although a genetic mosaicism has been proposed. While the majority of cases are sporadic, several families with this condition have been documented. Only one report has described NC occurring in homozygous twins.²

Frequency

United States

Exact figures are lacking. NC is considered relatively rare. One dermatology department found 12 cases in 100,000 skin biopsy specimens. Another department reported an incidence of 1 case per 45,000 dermatology visits. The incidence of NC syndrome is even more difficult to estimate; it is considered less common than nonsyndromal NC.

Mortality/Morbidity

Most patients are asymptomatic. Uncommonly, the lesions become repeatedly inflamed and infected, leading to painful cysts, abscesses, fistula formation, and scarring. Additionally, patients may be distressed over the cosmetic appearance of the lesions.

Race

No racial predilection is recognized.

Sex

Males and females are equally affected.

Age

Approximately 50% of cases of NC are evident at birth, with the other 50% developing during childhood, usually before age 10 years. A few case reports describe onset later in life, including in the seventh decade. These cases usually occur after some form of trauma³ or a rash.

Clinical

History

The lesions are typically present at birth or develop in early childhood. They are usually asymptomatic. However, one case report described itching as an accompanying symptom. Patients usually seek help for cosmetic reasons. The lesions grow as the patient does and often grow faster at puberty. Patients may be able to express keratinaceous material from the pores.

With the inflammatory form, repeated bacterial infections, drainage, cysts, fistula and abscess formation, and scarring may develop.

Physical

The lesion appears as a collection of discrete, dilated follicular ostia plugged with pigmented keratinaceous material. They can be single or multiple, usually unilateral, and range in size from a few centimeters to involving half of the entire body.

NC is typically found on the face, trunk, neck, and upper extremities. Rarely, it has been described on the palms⁴ and soles or penis.⁵ When it occurs on the elbows and knees, it can appear as verrucous nodules.

NC may be linear, interrupted, unilateral, bilateral, present in a dermatomal distribution, following the lines of Blaschko, or segmental.

NC syndrome is the association of NC with abnormalities in the central nervous system, skeletal system, skin, and eyes, as follows:  

• Central nervous system - Epilepsy, electroencephalogram abnormalities, transverse myelitis, microcephaly
• Skeletal system - Scoliosis, hemivertebrae, spina bifida occulta, foot deformities, absent fifth finger, syndactyly, supernumerary digits
• Skin - Ichthyosis, trichilemmal cysts, leukoderma, white hairs, Sturge-Weber syndrome, hemangiomas, linear basal cell nevus
• Eye - Congenital cataracts (unilateral and bilateral)
• Other - Multiple basal cell carcinomas, rare systemic malignancies

Causes

The cause is unknown.