Excerpt from Eruptive Vellus Hair Cysts

Synonyms, Key Words, and Related Terms: follicular papules, vellus cyst, eruptive cyst, EVHC, vellus hair follicle abnormality, acneiform eruption, pachyonychia congenita, hidrotic ectodermal dysplasia, steatocystoma multiplex, epidermoid cysts, hybrid cysts

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Background

Eruptive vellus hair cysts (EVHCs) were first described in 1977 by Esterly and colleagues who reported 2 children with symmetrically distributed follicular papules on the chest and flexor extremities.¹ Histologically, these papules had the unique characteristic of dermal cysts containing small vellus hairs.

Cases of EVHC may either be acquired or inherited in an autosomal dominant fashion. Generally, they are isolated findings. However, they have been associated with other skin disorders (eg, anhidrotic ectodermal dysplasia, hidrotic ectodermal dysplasia, pachyonychia congenita).

Pathophysiology

EVHCs are thought to arise as a developmental abnormality of vellus hair follicles. A predisposition exists for follicular occlusion at the level of the infundibulum, which results in cystic dilatation of the proximal hair follicle and secondary atrophy of the hair bulb.

Frequency

International

The frequency is unknown. More than 50 cases have been reported in the literature; however, EVHCs may occur more frequently than is suggested by reports, possibly because the diagnosis is only definitively confirmed with biopsy.

Mortality/Morbidity

EVHCs are asymptomatic; however, they may be cosmetically bothersome. Morbidity may be associated with treatment of the disorder.

Race

EVHCs have no racial predilection.

Sex

Males and females are affected equally.

Age

In familial cases, EVHCs are first noted at birth or during infancy. In sporadic cases, cysts usually develop in the late-first or second decade of life.

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