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Eruptive vellus hair cysts.

The patient was diagnosed with eruptive vellus hair cysts (EVHC). Treatment with a keratolytic, such as 12% lactic acid cream, was recommended. Hydrocortisone 2.5% once daily as needed also was recommended to treat the patient's itch.

EVHC are benign middermal cysts characterized by epidermoid keratinization of the cyst wall, as well as lamellar keratin and vellus hairs within the cyst. (1) The term "eruptive vellus hair cysts" was first used to describe a longstanding hyperpigmented, monomorphous papular eruption in two children by Esterly, Fretzin, and Pinkus in 1977. (2)

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Clinically, EVHC present as 1- to 3-mm follicular, dome-shaped papules that are often skin-colored but also have been described as being brown, gray, green, or black colored. (3,4) They appear suddenly and sometimes are associated with mild tenderness and pruritus. (1-5) EVHC most commonly present on the anterior chest but also can present on the upper and lower extremities, face, neck, axillae, and buttocks. (4)

The exact pathogenesis of EVHC has not been fully elucidated, although an autosomal dominant mode of inheritance has been reported in some cases, and an association with mutations in genes encoding keratin 17 and keratin 6b has been noted. (6,7,8)

Notably, inherited keratin mutations causing type 2 pachyonychia congenita can produce EVHC along with a characteristic nail dystrophy, focal palmoplantar keratoderma, follicular keratosis, and multiple steatocysts. (4) Keratin 17 is expressed in pilosebaceous ducts, and EVHC have been observed in patients with other lesions involving the pilosebaceous duct--particularly infantile milia and steatocystoma multiplex. (9) The authors of a 2012 review noted that pilosebaceous and apocrine glands are distributed in a pattern that overlaps broadly with locations at which EVHC have been noted and opined that such overlap is unlikely to be random. (3)

EVHC most commonly occurs in the first three decades of life, although onset has been reported as late as a patient's mid-50s. (10)

Furthermore, although spontaneous resolution is possible through transepidermal elimination of cyst products, cases may persist for years in the absence of treatment. (1)

Accurate diagnosis of eruptive vellus hair cysts is important to guide therapy

Keratosis pilaris consists of follicular-based papules with variable erythema. (4) It may be widespread--including over the anterior chest--but is most commonly seen on the cheeks, extensor surfaces of proximal upper extremities, and the anterior thighs. (4) It is related to excessive keratinization, which leads to formation of horny plugs within hair-follicle orifices. (1)

Steatocystoma multiplex is typically characterized by firm, yellow-to-flesh-colored dermal cysts ranging from a few millimeters to 1 cm in size. (1) They are sometimes clinically hard to distinguish from EVHC, and both are associated with keratin 17 gene mutations and type 2 pachyonychia congenita. (1) Nonetheless, this patient's lesions did not have any features--such as size or drainage--that would point toward steatocystoma multiplex or other skin findings suggestive of pachyonychia congenita.

Superficial folliculitis, also known as Bockhart's impetigo, is an infection of the follicular ostium and typically presents with perifollicular pustules on an erythematous base that may be painful or pruritic and can occur throughout the corpus, including the anterior trunk. (1)

Acne vulgaris is a very common disease that involves the pilosebaceous unit and occurs most frequently on the face, back, upper arms, and chest. However, it is characterized by open and closed comedones, papules, and pustules and, in severe cases, nodules and cysts that may leave postinflammatory hyperpigmentation and scarring. Tiny, hyperpigmented, dome-shaped macules occurring exclusively on the chest would not be characteristic.

Patients with hypohidrotic ectodermal dysplasia, also known as Christ-Siemens-Touraine syndrome, can present with EVHC. This condition is characterized by a triad of fair, sparse short hair; hyperthermia related to decreased sweating; and missing teeth. (4) Although EVHC have been reported in association with hypohidrotic ectodermal dysplasia, this patient does not have any of the dysmorphic features associated with this syndrome. (11)

Patients with pachyonychia congenita (type 2) also may have EVHC as part of their presentation, but this patient does not have nail dystrophy, focal palmoplantar tar keratoderma, follicular keratoses, or multiple steatocysts, which also are features of this condition. (4)

Treatment may be offered to patients who are distressed by the lesions or seek cosmesis. A 2012 review of 220 cases of EVHC found that topical retinoic acid, incision/excision, C[O.sub.2] laser, erbium:yttrium-aluminum-garnet laser, needle evacuation, dermabrasion, and 10% urea cream were each associated with successful treatment in multiple cases. (3)

Forty years have passed since EVHC was identified as a distinct disease entity. Despite this, eruptive vellus hair cysts remains somewhat understudied, and further research is needed to determine an ideal treatment algorithm for patients with this condition.

Our approach was to attempt noninvasive keratolytic therapy before considering retinoids or surgical options; we also recommended steroid treatment for symptom relief.

Providers should keep EVHC in the differential for eruptions consisting of tiny papules so that appropriate treatment may be offered.

BY CATALINA MATIZ, MD, AND AYAN KUSARI

Dr. Matiz is a pediatric dermatologist at Rady Children's Hospital, San Diego, and an assistant clinical professor in the department of pediatric and adolescent dermatology at the University of California, San Diego. Mr. Kusari is a medical student at the University of California, San Diego. Dr. Matiz and Mr. Kusari said they had no relevant financial disclosures. Email them at pdnews@frontlinemedcom.com.

References

(1.) Dermatology. 3rd ed. (Philadelphia: Saunders, 2012).

(2.) Arch Dermatol. 1977 Apr;113(4):500-3.

(3.) Am J Clin Dermatol. 2012 Feb 1;13(1):19-28.

(4.) Hurwitz Clinical Pediatric Dermatology: A Textbook of Skin Disorders of Childhood and Adolescence. 4th ed. (Philadelphia: Saunders, 2011).

(5.) Indian Dermatol Online J. 2013 Jul;4(3):213-5.

(6.) J Am Acad Dermatol. 1980 Oct;3(4):425-9.

(7.) Am J Dermatopathol. 1997 Jun;19(3):250-3.

(8.) Hum Mol Genet. 1998 Jul;7(7):l 143-8.

(9.) Dermatology. 1998;196(4):392-6.

(10.) Arch Dermatol. 1986 Feb;122(2):141.

(11.) Int J Dermatol. 2001 Jun;40(6):401-2.
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Title Annotation:Pediatric Dermatology Consult
Author:Matiz, Catalina; Kusari, Ayan
Publication:Pediatric News
Date:Aug 1, 2017
Words:993
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