Enduring eruption of papules on the chest

Eruptive vellus hair cystsEruptive vellus hair cysts, first described by Esterly, Fretzin, and Pinkus in 1977,1have been reported most commonly in children and young adults.2The average age of diagnosis is age 24 years, with 90% of cases diagnosed in persons...

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Eruptive vellus hair cysts, first described by Esterly, Fretzin, and Pinkus in 1977,¹have been reported most commonly in children and young adults.²The average age of diagnosis is age 24 years, with 90% of cases diagnosed in persons younger than age 35 years.²Males and females are equally affected.²No racial or ethnic predilection has been observed.² 

The pathogenesis of eruptive vellus hair cysts is unknown. Although its occurrence is typically sporadic, familial cases of eruptive vellus hair cysts have been described.²Familial eruptive vellus hair cysts are inherited in an autosomal dominant fashion, but no underlying mutation has been identified to date.²

Eruptive vellus hair cysts are characteristically seen in the setting of steatocystoma multiplex and pachyonychia congenita. Steatocystoma multiplex is an autosomal dominant disorder caused byKRT17mutations encoding keratin 17, expressed in the nail bed, hair follicles, and sebaceous glands.³ 

Pachyonychia congenita is also an autosomal dominant genodermatosis, historically classified into pachyonychia congenita types 1 and 2. According to this old classification system, eruptive vellus hair cysts occur more commonly in pachyonychia congenita type 2 with mutations inKRT6BandKRT17, encoding keratin 6B and keratin 17, respectively.

Eruptive vellus hair cysts present with the sudden onset of many small (1 mm to 7 mm) dome-shaped papules of variable color.³The papules often are skin-colored but also can be darkly pigmented.³Individual papules are follicularly based.² 

Eruptive vellus hair cysts tend to be symmetric and generalized.²The lesions usually are not grouped.⁴The most common locations are the anterior chest and central abdomen.^3,4Less common locations include the upper and lower extremities, face, neck, posterior trunk, and/or buttocks.⁴ 

The pinna of the ear may be affected, but this is rare. Eruptive vellus hair cysts on the face can be hyperpigmented and reportedly have been misdiagnosed as a nevus of Ota.⁴ 

Lesions are usually asymptomatic, but may occasionally become inflamed and subsequently pruritic. Rarely, only a solitary lesion may be present. These lesions typically persist indefinitely.³

On rare occasions, some lesions may resolve through transepidermal elimination of the cyst products.³Cyst contents may be induced by pressure as well.²Eruptive vellus hair cysts developing in later adulthood have been reported in the setting of chronic renal failure.⁵

The diagnosis of eruptive vellus hair cysts is often made on clinical grounds alone. However, when the diagnosis is in question, a skin biopsy is diagnostic. Histopathologic examination reveals a small cystic structure in the dermis, lined by stratified squamous epithelium.³ 

The lining shows epithelial keratinization with a granular layer.^2,3The cyst contents include loose laminated keratin and numerous vellus hairs.³A less commonly used diagnostic technique is the application of a topical anesthetic, followed by a tiny incision at the top of the suspected vellus hair cyst to express the contents. The contents are then microscopically examined for the presence of vellus hairs.⁴

Syndromes that are associated with eruptive vellus hair cysts include steatocystoma multiplex and pachyonychia congenita type 2. In steatocystoma multiplex, multiple steatocystomas with eruptive vellus hair cysts are the hallmark of this genodermatosis.

Steatocystomas present as soft subcutaneous nodules, measuring from a few millimeters to a centimeter in diameter.³The most common locations are the chest, forearms, axillae, and groin.³If punctured, the steatocystomas drain an oily fluid.³Steatocystomas are usually asymptomatic and tend to persist indefinitely.³

Pachyonychia congenita type 2 (PC2) is characterized by distinctive “omega nails” caused by wedge-shaped nail-bed thickening with elevation of the nail plate, non-premalignant oral leukokeratosis, and variable palmoplantar keratoderma in addition to steatocystomas and eruptive vellus hair cysts. 

Other clinical features of PC2 include follicular keratoses, natal/prenatal teeth, and pili torti or other hair abnormalities.³

Eruptive vellus hair cysts have rarely been described in the settings of hidrotic ectodermal dysplasia (Clouston syndrome), hypohidrotic ectodermal dysplasia (Christ-Siemens-Touraine syndrome), and Lowe syndrome (oculocerebrorenal syndrome).⁵

Hidrotic ectodermal dysplasia presents with diffuse palmoplantar keratoderma, hypotrichosis, and nail dystrophy. Patients with hypohidrotic ectodermal dysplasia are easily recognized by their facial features (saddle nose, full everted lips, frontal bossing, and periorbital wrinkling), peg-shaped teeth, hypohidrosis, and sparse hair.

Lowe syndrome is characterized by renal failure (renal Fanconi syndrome), mental retardation, and eye abnormalities (most commonly, bilateral congenital cataracts).

Patients with Lowe syndrome also are noted to have small bone structure, often secondary to hypophosphatemic rickets in the setting of renal failure, and poor dentition. Eruptive vellus hair cysts have been reported in the literature only once in a 20-year-old patient with Lowe syndrome.⁶

The differential diagnosis of eruptive vellus hair cysts includes milia, molluscum contagiosum, syringomas, folliculitis, and keratosis pilaris.⁴Milia are white, dome-shaped papules most commonly located on the face. Molluscum contagiosum are often grouped and commonly have an umbilicated center, unlike the discrete lesions of eruptive vellus hair cysts that are often hyperkeratotic. 

Syringomas are firm, skin-colored papules. They are most characteristically seen on the periorbital area, but can be seen on the upper trunk. Syringomas are typically larger than eruptive vellus hair cysts and have no associated hyperkeratosis. 

Although folliculitis is common on the chest, it is notable for pustules, which are not seen in eruptive vellus hair cysts. Although individual lesions of keratosis pilaris are similar to those of eruptive vellus hair cysts, keratosis pilaris is predominantly located on the lateral proximal upper and lower extremities. A biopsy will definitively differentiate all of these entities from eruptive vellus hair cysts.

If lesions are asymptomatic and not cosmetically bothersome, no treatment is necessary or recommended. For patients desiring treatment, “incision of individual cysts and expression of their contents followed by gentle curettage, light electrodesiccation with expression of contents, therapy with topical vitamin A acid (tretinoin), lactic acid (12% lotion) or laser” have been reported.⁴Tazarotene 0.1% cream has also been reported to lead to clinical improvement.⁵

Our patient was asymptomatic and unconcerned by the appearance of her eruptive vellus hair cysts, so reassurance was provided and no treatment was initiated. n


Audrey Chan, MD, is a third-year dermatology resident at Baylor College of Medicine in Houston.


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HOW TO TAKE THE POST-TEST: This Clinical Advisor CME activity consists of 4 articles. To obtain credit, you must also read Scaly plaques after 
onychomycosis therapy,
 Annular eruption on the lower leg
 and Enduring eruption of papules on the chest. Then take the post-test here.

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References


1. Esterly NB, Fretzin DF, Pinkus H. Eruptive vellus hair cysts. Arch Dermatol. 1977;113(4):500-503.
2. Patel U, Terushkin V, Fischer M, et al. Eruptive vellus hair cysts. Dermatol Online J. 2012;18(12):7. Available at http://escholarship.org/uc/item/0dz2b51s; accessed May 15, 2014.
3. Bolognia JL, Jorizzo JL, Rapini RP, eds. Dermatology. 3rd ed. St. Louis, Mo.: Elsevier-Mosby; 2008:Chap. 111.
4. Paller AS, Mancini AJ. Hurwitz. Clinical Pediatric Dermatology. 4th ed. Philadelphia, Pa.: Saunders Elsevier; 2011:154.
5. James WD, Berger TG, Elston DM. Andrews’ Diseases of the Skin. 11th ed. Philadelphia, Pa.: Saunders Elsevier; 2011:671.
6. Nandedkar MA, Minus H, Nandedkar MA. Eruptive vellus hair cysts in a patient with Lowe syndrome. Pediatr Dermatol. 2004;21(1):54-57.