Eruptive vellus hair cyst

Eruptive vellus hair cysts (EVHC) are a relatively uncommon dermatological condition characterized by the development of small, skin-colored, dome-shaped papules. These cysts predominantly arise on the chest and extremities and are most commonly observed in children and young adults. The condition was first described in the medical literature in 1977 by Esterly, Fretzin, and Pinkus.

Etiology and Pathogenesis

The exact cause of eruptive vellus hair cysts remains unclear, but they are believed to result from the obstruction of vellus hair follicles. This obstruction is thought to be due to a developmental defect in the follicle, leading to the accumulation of keratin and other debris, and subsequently, cyst formation. There is some evidence to suggest a genetic component to the condition, as cases have been reported in siblings and in successive generations.

Clinical Features

Eruptive vellus hair cysts typically present as multiple, small (1-4 mm in diameter), firm, skin-colored to slightly bluish papules. These lesions are most commonly found on the chest, upper arms, and thighs, but can also appear on the abdomen, back, and face. The cysts are generally asymptomatic, but can occasionally become inflamed or infected, leading to discomfort or tenderness.

Diagnosis

The diagnosis of eruptive vellus hair cysts is primarily clinical, based on the characteristic appearance of the lesions. Dermoscopy can aid in the diagnosis, revealing specific features such as a central hair shaft. Histopathological examination of a biopsy specimen is the definitive diagnostic method, showing a cystic structure in the dermis filled with laminated keratin and vellus hairs.

Treatment

Treatment of eruptive vellus hair cysts is not always necessary, as the condition can be asymptomatic and may resolve spontaneously. However, for cosmetic reasons or in cases of discomfort, several treatment options are available. These include manual extraction of the cyst contents, laser therapy (such as with a carbon dioxide laser), and topical or intralesional steroids to reduce inflammation. Retinoids, both topical and systemic, have also been used with varying degrees of success.

Prognosis

The prognosis for individuals with eruptive vellus hair cysts is generally good. While the condition may persist for years, spontaneous resolution has been reported. Treatment can help to alleviate symptoms and improve the appearance of the skin, but recurrence after treatment is not uncommon.