Nevus comedonicus is a rare cutaneous hamartoma characterized by clusters of dilated follicular openings filled with keratinous material, clinically resembling grouped open comedones. It is considered a developmental abnormality of the pilosebaceous unit and typically presents at birth or during early childhood, although delayed onset cases have been reported. The condition may occur as an isolated skin finding or as part of a broader systemic involvement known as nevus comedonicus syndrome.
Clinical Presentation
Clinically, nevus comedonicus appears as multiple, closely grouped, dilated follicular pits containing dark keratin plugs. These lesions are often arranged in a linear, segmental, or zosteriform pattern following the lines of Blaschko. The most commonly affected sites include the face, neck, trunk, and upper extremities.
In the image presented, there are numerous clustered, darkly pigmented, comedone-like lesions localized around the perioral region. The lesions show uniform follicular dilation with keratinous plugs, giving a characteristic “honeycomb” or “blackhead-like” appearance. Surrounding skin may appear normal or mildly inflamed. Occasional secondary changes such as erythema, pustule formation, cysts, or scarring may occur due to inflammation or secondary infection.
Pathogenesis
The exact pathogenesis of nevus comedonicus remains unclear. It is believed to result from somatic mutations affecting follicular development, leading to abnormal keratinization and follicular occlusion. Genetic mosaicism is thought to play a role, explaining the localized and patterned distribution of lesions. Unlike acne vulgaris, nevus comedonicus is not driven by hormonal influence or increased sebum production.
Histopathology
Histological examination typically reveals markedly dilated follicular infundibula filled with lamellated keratin. Sebaceous glands are often absent or underdeveloped, and there is minimal involvement of the surrounding dermis unless secondary inflammation is present. These findings help differentiate nevus comedonicus from acneiform eruptions and other follicular disorders.
Differential Diagnosis
Several conditions may resemble nevus comedonicus and should be considered in the differential diagnosis:
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Acne vulgaris – Usually more diffuse, inflammatory, and hormonally influenced
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Favre–Racouchot syndrome – Occurs in elderly patients with sun-damaged skin
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Chloracne – Associated with chemical exposure
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Steatocystoma multiplex – Characterized by cystic lesions rather than open comedones
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Epidermal nevus – Lacks comedonal plugs
The early onset, grouped distribution, and persistence of lesions favor a diagnosis of nevus comedonicus.
Associated Syndromes
In rare cases, nevus comedonicus may be associated with systemic abnormalities, forming nevus comedonicus syndrome. Reported associations include skeletal defects, ocular abnormalities, neurological manifestations, and developmental delays. Therefore, patients—especially children—with extensive or atypical lesions may warrant further systemic evaluation.
Management and Treatment
Treatment of nevus comedonicus is often challenging and largely depends on the severity, extent, and presence of symptoms. Asymptomatic lesions may not require intervention. For cosmetic or inflammatory concerns, available treatment options include:
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Topical retinoids (e.g., tretinoin, adapalene) to reduce follicular plugging
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Keratolytic agents such as salicylic acid or ammonium lactate
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Manual extraction of keratin plugs (temporary benefit)
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Laser therapy (CO₂ or Er:YAG lasers) for localized lesions
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Surgical excision for small, well-demarcated areas
Inflamed or infected lesions may require topical or systemic antibiotics.
Prognosis
Nevus comedonicus is a benign condition with no malignant potential. However, it is typically persistent and may gradually enlarge over time. Prognosis is generally good, particularly in isolated cutaneous cases. Early recognition and appropriate management can help minimize complications such as scarring and recurrent infections.
Conclusion
Nevus comedonicus is an uncommon but distinctive follicular disorder marked by grouped comedone-like lesions. Recognition of its characteristic clinical features is essential to distinguish it from more common acneiform conditions. Although treatment remains primarily cosmetic and symptomatic, advances in laser therapy and topical treatments have improved outcomes for many patients. A multidisciplinary approach may be necessary in cases associated with systemic involvement.
