Eruptive vellus hair cyst
Description, Causes and Risk Factors:
Eruptive vellus hair cysts (EVHC) are characterized by multiple small asymptomatic yellowish or brownish papules with a smooth or centrally umbilicated surface. Their diameters range from 1 to 5 mm. They are usually localized on the chest and proximal extremities, but they may be present at unusual sites, including the face1-10, groin and buttocks10-12. Histologic examination reveals that the cysts are found in the mid-dermis, they are lined by several layers of squamous epithelium and they are filled with cutting vellus hair shafts and laminated keratin materials.
The exact pathogenesis of Eruptive vellus hair cyst is unknown, but some theories for it have been proposed. Researchers suggested that this condition might arise as a developmental abnormality of the vellus follicles, resulting in occlusion at the infundibular level. This would cause the cyst to retain hairs and keratin. In contrast, researchers also suggested that the EVHC is a hamartoma of the pilosebaceous unit. Several authors have referred to the close relationship of between the EVHC and steatocystoma multiplex (SM). They suggested that both EVHC and SM may result from a cystic change of the pilosebaceous duct and so they may represent a spectrum of the same clinical entity. Some case reports have described the simultaneous presence of Eruptive vellus hair cyst and SM at one biopsy site or a hybrid cyst showing the combined histopathologic features of EVHC and SM11. However, the cytokeratin studies have shown that the EVHC expresses K17, but not K10, whereas the SM expresses both K17 and K1018, suggesting that Eruptive vellus hair cyst and SM are distinct entities and they are not variants of one disorder.
Eruptive vellus hair cyst may occur sporadically or be inherited in an autosomal dominant fashion. The majority of cases are isolated and benign findings. However, there are reports of EVHC occurring in association with renal failure and with such disorders as anhidrotic ectodermal dysplasia
, hidrotic ectodermal dysplasia, pachyonychia congenita
, and Lowe syndrome.
In most cases, Eruptive vellus hair cyst is found on the anterior chest wall, abdomen and/or extremities, yet other unusual sites can be involved. Researchers experienced a localized form of EVHC on the forehead and they called it the facial variant, and there has since been several case reports of such facial variants. Less than 15 cases of the so-called facial variant form of EVHC, which is localized exclusively on the face, have been reported. There have also been a few cases on an unusual site such as the buttocks.
Eruptive vellus hair cystusually present as small red or brown bumps over the sternum. They have also been reported to occur on the limbs. There may be few to numerous cysts, sometimes numbering in the hundreds. Individual lesions are usually small smooth dome-shaped papules, 2-3mm in size. They may be dimpled or umbilicated and sometimes have a scaly or crusty surface.
Diagnosis of Eruptive vellus hair cyst is confirmed by examination of a cutaneous biopsy specimen, which shows a mid-dermal cyst that contains laminated keratin and multiple transversely- and obliquely-cut vellus hairs. A flattened squamous epithelium lines the cyst wall. Ruptured cysts demonstrate a granulomatous reaction in the adjacent dermis. An alternative, less invasive diagnostic approach has been described in which a superficial incision at the top of the lesion enables expression of the cystic contents. Microscopic examination of the expressed contents in a potassium hydroxide preparation shows numerous vellus hairs.
Twenty-five percent of eruptive vellus hair cyst (EVHC) cases resolve spontaneously through transepidermal elimination.
Keratolytic treatment is as follows: Clinical benefit was reported after gentle mechanical dermabrasion with an exfoliating sponge followed by an application of 10% urea cream. Significant clinical improvement resulted in one case with 12% lactic acid applied to the affected areas.
Retinoid treatment is as follows: Topical tretinoin applied nightly to the affected area is a reasonably safe treatment option. This method reportedly cleared a case of congenital Eruptive vellus hair cyst after only 5 applications, leaving only a slight residual erythema that gradually faded.
Topical tazarotene cream 0.1% applied to the affected area was shown to be more effective than some surgical options for the treatment of EVHC. Oral isotretinoin at 1 mg/kg/d produced no improvement in one patient after 20 weeks of therapy.
Systemic vitamin A therapy (100,000 IU/d) has also been tried; however, this also produced no clinical improvement and resulted in severe headaches requiring discontinuation of therapy. Calcipotriene treatment has been reported. A single case report showed a partial response of Eruptive vellus hair cysts after a 2 months treatment course with topical calcipotriene.
Needle evacuation of eruptive vellus hair cysts (EVHCs) can be performed using an 18-gauge needle after local anesthesia with a topical anesthetic (EMLA cream). This technique can also be used to aid in the diagnosis of EVHC. After extrusion, the cyst is examined histologically, pressed between a glass slide and cover slip with mineral oil. Multiple thin, fine hairs can be seen within the lumen of the thin cyst wall.
Simple excision (eg, punch biopsy technique) removes the cyst; however, this is not practical for most cases of EVHCs because the cysts are too numerous and punch biopsy scars may be unsightly.
For more specialized treatment option consult Dermatologist.
NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.