Are You Confident of the Diagnosis?
Characteristic findings on physical examination
Eruptive vellus hair cysts commonly present in childhood with the development of numerous papules on the chest and flexoral arms. Single and multiple lesions have also been described involving many other areas, including the face, back, abdomen, and vulvar labia. Most lesions are asymptomatic and of cosmetic concern only. Pruritus has been reported. Eruptive vellus hair cysts are usually 1-4 mm smooth brown or red-brown papules with no epidermal disruption (Figure 1). Cases with umbilication, hyperkeratosis, and epidermal elimination have been reported.
Expected results of diagnostic studies
Histologic evaluation of a biopsy demonstrates a middermal cysts lined by stratified squamous epithelium (Figure 2). Cysts contain laminated keratin and multiple small vellus hairs (Figure 3). A granulomatous inflammatory reaction may be present.
Some have suggested that the diagnosis can be confirmed by incising the surface of a cysts, expressing the contents and examining them microscopically with potassium hydroxide. The presence of multiple vellus hairs suggests the diagnosis of vellus hair cysts.
Steatocystoma multiplex may also present with numerous small papules scattered on the chest and flexor arms. Steatocystoma simplex and multiplex may contain vellus hairs; however, steatocystomas contain sebaceous lobules within the cysts wall and have a thin pink cuticular lining. Dermoid cysts may also contain hair; however, they are easily differentiated by the presence of multple adnexal structures within the cysts wall.
Who is at Risk for Developing this Disease?
Most cases of eruptive vellus hair cysts present in childhood; however, cases have been reported from infancy through adulthood.
What is the Cause of the Disease?
The pathogenesis of eruptive vellus hair cysts remains unclear. Multiple authors have proposed that plugging of a vellus follicle leads to vellus hair retention and cystic dilatation.
Reports of familial cases suggest a possible genetic abnormality in vellus follicles in at least some cases; most are sporadic in nature, but reports of autosomal dominant inheritance has been reported. While there are histologic similarities between eruptive vellus hair cysts and steatocystoma, differential keratin expression between the two entities suggests that they are distinct.
Systemic Implications and Complications
Eruptive vellus hair cysts are of cosmetic concern and have no systemic implications.
Treatment of eruptive vellus hair cysts is often unsatisfactory. Fortunately, up to 25% of cases spontaneously resolve. Surgical treatment by excision, incision and drainage, or by destruction by dermabrasion and ablative lasers is effective but may result in unacceptable scarring. Topical therapy with retinoids and keratolytics may be effective in some cases but has not been evaluated in a controlled fashion. Medical therapy with isotretinoin and Vitamin A has not been effective..
Optimal Therapeutic Approach for this Disease
Some patients, or their parents, presenting with eruptive vellus hair cysts will be satisfied to get a diagnosis and know that the lesions are benign. However, many may request treatment due to cosmetic concerns. In a child with a classic presentation of numerous small cysts on the chest and arms, the parents may be counseled that spontaneous resolution occurs in a significant fraction of patients and “watchful waiting” is appropriate. The use of topical retinoids (tretinoin 0.05% cream daily or tazarotene 0.1% cream daily) or keratoytics (12% lactic acid lotion or 10 – 20% urea cream), may provide some benefit and are unlikely to cause harm.
Surgical excision and destructive modalities may be offered to those patients who have have persistent lesions that cause significant distress. Isolated and localized lesions are much more amenable to surgical treatment. The patient must be counseled that scarring is likely with any method, and the excision or destruction of a limited number of lesions initially is appropriate Laser ablation with CO2 and ER:Yag has been used. The remission is short as relapse is almost always the end result.
Eruptive vellus hair cysts require no long-term management. When deciding whether and how to treat a patient with eruptive vellus hair cysts, the patient, the parents of a minor patient, and the physician must consider the benefits of treating a cosmetically bothersome condition against the cost and potential scarring of treatment.
Unusual Clinical Scenarios to Consider in Patient Management
The differential diagnosis of a child presenting with numerous small papules is broad and includes eruptive vellus hair cysts, steatocystoma multiplex, molluscum contagiosum, milia, folliculitis, and acne among others. If the diagnosis is not apparent, microscopic examination of cysts contents using potassium hydroxide may be considered; however, a biopsy may be required to make a specific diagnosis.
Eruptive vellus hair cysts have been rarely reported in pachyonychia congentia, Lowe syndrome (oculo-cerebral- renal syndrome, caused by a mutation in the OCRL1 gene), and some ectodermal dysplasias.
They have been reported in unusual locations such as the genitalia.
What is the Evidence?
Bovenmyer, DA. “Eruptive vellus hair cysts”. Arch Derm. vol. 115. 1979. pp. 338-9. (This was published soon after the original description. It adds more cases to the literature.)
Esterly, NB, Fretzin, DF, Pinkus, H. “Eruptive vellus hair cysts”. Arch Derm. vol. 113. 1977. pp. 500-3. (The original article describing eruptive vellus hair cysts, reporting two children with eruptive papules on the trunk.)
Hana, T, Wataru, F, Jiro, A. “Expression of keratins (K10 and K17) in steatocystoma multiplex, eruptive vellus hair cysts, and epidermoid and trichilemmal Cysts”. Am J Dermatopathol. vol. 19. 1997. pp. 250-3. (Dermatopathology review of various cysts. Describes distinguishing and unique features of all.)
Hong, SD, Frieden, IJ. “Diagnosis eruptive vellus hair cysts”. Pediatr Dermatol. vol. 18. 2001. pp. 258-9. (Case report of eruptive vellus hair cysts with review of the literature.)
Karen, JK, Heller, M, Wee, SA, Mikkilineni, R. “Eruptive vellus hair cysts”. Dermatol Online J. vol. 13. 2007. pp. 14(Reviews the literature and gives a nice short overview of eruptive vellus hair cysts.
Park, JH, Her, Y, Chun, BM, Kim, CW, Kim, SS. “A case of eruptive vellus hair cysts that developed on the labium major”. Ann Dermatol. vol. 21. 2009. pp. 294-6. (Case report and review. The authors describe eruptive vellus hair cysts in an unusual location.
Morgan, MB, Kouseff, BG, Silver, A. “Eruptive vellus hair cysts and neurologic abnormalities: two related conditions”. Cutis. vol. 47. 1991 Jun. pp. 413-5. (Report of a child with seizures/neurological disorder that subsequently developed eruptive vellus hair cysts. The authors suggested this may be an as yet unreported syndrome.)
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