Nevus Comedonicus Syndrome (NCS)

Nevus comedonicus syndrome is one of the epidermal nevus syndromes, but is extremely rare. There is no gender or racial difference in the prevalence of this condition. The prevalence ranges from 1 in 45,000 - 100 000. Nevus comedonicus syndrome (NCS) was described under this name in 1978.  It consists of the following findings:

• Nevus comedonicus
• Ipsilateral cataract
• Skeletal defects
• Brain defects
• Trichilemmal cysts

Clinical Manifestations

Nevus Comedonicus

The nevus was described in 1895 under the term “comedo nevus.” The typical lesion is an overgrowth of clumps of papules, usually with a central black firm center. These are morphologically blackheads, later evolving into inflammatory acne. For this reason, later lesions may appear nodular, pustular or abscessed. Significant scar formation is a natural post-inflammatory sequel of these lesions.

The lesions are formed by obstruction of the hair follicle canal, leading to the accumulation of black keratinized material within dilated follicular openings arranged close together. This material is not easily taken out. In most cases the lesions follow a linear or band-like pattern, but occasionally Blaschko lines are followed, or no pattern is recognizable.

While the condition presents any time between the time of birth and middle age, the most common time of its appearance is at birth (in half the cases) or at least before the age of 10 years. The most common site is in the face and neck. The lesion is usually free of any symptoms. It has various patterns of distribution. In a very few cases, multiple follicular basal cell carcinomas have been reported.

Extracutaneous Manifestations

Non-cutaneous anomalies are reported including:

• Skeletal: absence of fifth digit, rudimentary toe, scoliosis, polysyndactyly, bone hypertrophy, bone cyst, and vitamin D-resistant rickets are some of the bone defects that have been reported so far.
• Dental: oligodontia has been noted in one case.
• Glandular: eccrine spiradenoma, follicular basal cell nevus, and hidradenoma are sometimes seen.
• Central nervous system: microcephaly, brain malformations including agenesis of the corpus callosum, Sturge-Weber syndrome.
• Ocular: cataract, usually ipsilateral, but rarely bilateral.
• Trichilemmal cysts: these are cysts that form from hair follicles usually on the scalp, and are filled with keratin.

Diagnosis and Treatment

Conservative treatment of nevus comedonicus is given first, especially if there is inflammation or irritation. Treatment is with emollients, topical steroids and keratolytic lotions. Retinoids alone or in combination with topical steroids have been tried with mixed success. Newer drugs include FGFR inhibitors and IL-1α inhibitors, as well as tazarotene and calcipotriene.

Nevus comedonicus may require removal for cosmetic reasons or if severe inflammation sets in. surgical excision, shave excision, comedo extraction, or dermabrasion are some of the modalities adopted. Large lesions may require proper drainage, transplantation to fill the defect, or other measures for better cosmetic outcomes. Laser treatment using Er-YAG or pulsed carbon dioxide are also being tested for this indication.

References

• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3276921/
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4533567/
• https://rarediseases.org/rare-diseases/epidermal-nevus-syndromes/