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.[2]
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).
Eruptive vellus hair cysts (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.[3]
It has been reported after application of minoxidil.[4]
Eruptive vellus hair cysts (EVHCs) occur as a developmental abnormality of vellus hair follicles. A gradual disruption occurs between the proximal and distal parts of the follicle, usually at the level of the infundibulum. This results in the retention of hairs, cystic dilatation of the proximal follicle, and subsequent atrophy of the hair bulb.
EVHCs have also been considered a type of follicular hamartoma. The cyst wall may consist of keratinization patterns from different levels of the follicular infundibulum. The keratinization is generally that of the epidermis or the outer root sheath, but foci of trichilemmal keratinization have also been reported.
The frequency is unknown. More than 50 cases have been reported in the literature; however, eruptive vellus hair cysts (EVHCs) may occur more frequently than is suggested by reports, possibly because the diagnosis is only definitively confirmed with biopsy.
Race
Eruptive vellus hair cysts (EVHCs) have no racial predilection.
Sex
Males and females are affected equally.
Age
In familial cases, eruptive vellus hair cysts (EVHCs) are first noted at birth or during infancy. In sporadic cases, cysts usually develop in the late-first or second decade of life.
Eruptive vellus hair cysts (EVHCs) are asymptomatic; however, they may be cosmetically bothersome. Morbidity may be associated with treatment of the disorder. Lesions may resolve spontaneously via transepidermal elimination of cyst contents.
Eruptive vellus hair cysts (EVHCs) typically develop as an acneiform eruption on the chest and extremities.[5] EVHCs have also been reported on the eyelids and periorbital skin,as well as the labium major.[6, 7, 8, 9] Often, no antecedent trauma or triggering factor is reported. EVHCs may be congenital or acquired. Several reports have noted familial cases in which the condition is thought to be inherited as an autosomal dominant trait.[10, 11, 12] EVHCs may be present at birth or arise in childhood. In sporadic cases, lesions typically arise in the first and second decades with the onset of puberty.
Eruptive vellus hair cysts (EVHCs) appear clinically as discrete follicular papules. Papules may appear erythematous, yellow, bluish-gray, or even slightly brown. The chest and flexor or extensor surfaces of the extremities are the most common sites of involvement. Generalized EVHCs and facial variants are reported. EVHCs may also be seen on the ears.[13] A single case report describes unilateral EVHCs of the face.[14]
Patients may have just a few cysts, or, often, they may have several hundred. More than 400 cysts were seen on a patient with generalized EVHC. Cysts are usually dome-shaped with a smooth surface, measuring 1-4 mm in diameter. Cysts sometimes demonstrate central puncta, hyperkeratotic crusts, or umbilication. Mechanical irritation of the cysts may produce transepidermal elimination of retained vellus hairs, similar to that seen in perforating folliculitis.
Note the images below.
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Clinical photo of eruptive vellus hair cysts showing involvement on the patient's chest.
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Eruptive vellus hair cysts in the axilla.
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The patient seen here is expanding his cheek with air to better demonstrate multiple eruptive vellus hair cysts on the face.
Punch biopsy of the skin is the diagnostic procedure of choice for eruptive vellus hair cysts (EVHCs).
Alternatively, the diagnosis can be confirmed with a potassium hydroxide wet mount of cyst contents extruded through a small incision. Microscopic examination of the cyst contents reveals vellus hairs. The cyst can be anesthetized with a local or topical anesthetic prior to incision with a sterile blade or 18-gauge needle.
In 2006, another extraction technique was described. Patients were treated with topical anesthetic prior to puncturing the surface of the cyst with a sharp-tipped electrocautery instrument. The cyst wall and contents were then dissected out with forceps and either sent to a pathology laboratory or examined microscopically with 10% potassium hydroxide to confirm the diagnosis of EVHC.[24]
A report indicated that dermoscopy can help to distinguish EVHC from acne and molluscum contagiosum.[25]
Histopathology of eruptive vellus hair cysts (EVHCs) shows a cystic structure in the mid dermis arising from the infundibulum of a hair follicle.[26] The cysts contain multiple cross-sections of vellus hairs and layered laminated keratinous material. They are lined by squamous epithelium 2- to 5-cells thick. Generally, no sebaceous glands are present in the cyst wall. A surrounding granulomatous reaction may be present, especially if the hairs disrupt the cyst wall.
The differential diagnosis of pilosebaceous cysts includes infundibular cysts, steatocystoma multiplex, and EVHCs. All 3 commonly affect the anterior chest and consist of asymptomatic papules or nodules. Obstructed or occluded follicles form the common infundibular cysts. These do not contain sebaceous glands or vellus hairs. The cysts of steatocystoma multiplex arise in the sebaceous duct and have a crenulated, eosinophilic, hyaline lining to the cyst wall where the granular layer is absent. Steatocystomas also contain sebaceous glands arising within the cyst wall.
Some authors believe that EVHC and steatocystoma multiplex are variants of the same disorder because both lesions have been reported in the same patient.[27] Other authors have defended their status as distinct entities based on different histologic patterns. One study showed EVHC lesions expresssed keratins 1 and 10, calretinin, and p63, but findings were negative for epithelial membrane antigen, filaggrin, and androgen receptors.[28] Another study demonstrated differential expression of keratins 10 and 17.[29] In 2 cases of EVHC, strong staining for keratin 17 was found but no staining for keratin 10 was evident. In 7 cases of steatocystoma, both keratin 10 and keratin 17 were expressed in the suprabasal cells of the cyst wall. In 5 epidermoid cysts, positive staining occurred only for keratin 10.
Several reports note patients having cysts containing elements of both EVHCs and steatocystoma multiplex.[30, 31, 32] The term hybrid cyst has been proposed to describe cysts containing combinations of EVHCs, steatocystoma multiplex, and epidermoid cysts. Some authorities argue that these cyst types all form from the pilosebaceous unit and are therefore all just a spectrum of the same disorder. Combinations of infundibular cysts, trichilemmal cysts, and pilomatricomas have also been described as hybrid cysts.
Note the images below.
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Histopathology of an eruptive vellus hair cyst showing a middermal cyst with squamous epithelium.
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A close-up view of the contents of an eruptive vellus hair cyst showing cross-sections of vellus hairs and laminated keratinous material.
Twenty-five percent of eruptive vellus hair cyst (EVHC) cases resolve spontaneously through transepidermal elimination.
Keratolytic treatment was reported as beneficial after gentle mechanical dermabrasion with an exfoliating sponge (eg, Buf Puf, 3M; St. Paul, Minn) 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 can be helpful. Topical tretinoin applied nightly to the affected area is a reasonably safe treatment option. This method reportedly cleared a case of congenital EVHC 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.[33] Oral isotretinoin at 1 mg/kg/d produced no improvement in one patient after 20 weeks of therapy.[34] 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 EVHCs after a 2 months treatment course with topical calcipotriene.[35]
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).[36] 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.
Carbon dioxide laser vaporization has been effective for a case of EVHC on the face.[37] A test spot was performed with the carbon dioxide laser (10,600-nm wavelength) at 5 watts of power, irradiance of 160 W/cm2, a 2-mm spot size, and a pulse duration of 0.2 seconds. No scarring occurred after treating the face in the same manner. Eyelid lesions were treated in the same manner except they used only 3 watts of power and 100 W/cm2 irradiance. Slight hyperpigmentation occurred at some of the treated sites; no hypertrophic scarring was noted. Cystic regeneration did not occur.
Pulsed erbium:yttrium-aluminum-garnet (Er:YAG) laser has been reported effective in treating 2 patients with EVHCs on the trunk.[38] The technique involved drilling with the Er:YAG laser (2940-nm wavelength) using a 2-mm spot size, 250-microsecond pulse duration at 60.5-63.7 J/cm2, and a 1.9- to 2-J pulse energy. Three to 5 stacked pulses were delivered, the cysts were expressed with digital pressure, they were extracted with forceps, the base of the cyst wall was further ablated with 3 pulses, and the area was allowed to heal by secondary intention. The follow-up evaluation was performed only by telephone interview; patients reported no scarring, discoloration, or recurrence of the cysts. However, another report has suggested early recurrence of the cysts after treatment with Er:YAG laser to EVHC on the face.[39]
A split face study compared the 2940 nm Er:YAG laser with a nonablative 1540 Er:Glass laser. The treatment period was 9 months, with treatment intervals of 6-12 weeks. The study found a reduction in total number of cysts with a tendency for better clinical outcome using the Er:YAG ablative laser.[40]
Clinical Context:
Ammonium lactate contains lactic acid, an alpha-hydroxy acid that has keratolytic action, thus facilitating release of comedones. Alpha-hydroxy acids cause disadhesion of corneocytes and thin the stratum corneum. Use 12% cream or lotion.
Clinical Context:
Urea is a topical humectant. It promotes hydration and removal of excess keratin. Urea is a small molecule that osmotically binds water. Use 10% or 20% cream.
Clinical Context:
Tazarotene is a retinoid prodrug whose active metabolite modulates differentiation and proliferation of epithelial tissue; it may also have anti-inflammatory and immunomodulatory properties. Tazarotene is available as 0.05% and 0.1% cream and gel.
Clinical Context:
Tretinoin topical is a topical retinoid that significantly alters the differentiation of keratinocytes. It inhibits microcomedo formation and eliminates lesions. It makes keratinocytes in sebaceous follicles less adherent and easier to remove. Tretinoin topical is available as 0.025%, 0.05%, and 0.1% creams and as 0.01% and 0.025% gels.
These agents stimulate cellular retinoid receptors and help normalize keratinocyte differentiation and are comedolytic. In addition, they have anti-inflammatory properties.
What are eruptive vellus hair cysts (EVHCs)?What is the pathophysiology of eruptive vellus hair cysts (EVHCs)?What causes eruptive vellus hair cysts (EVHCs)?What is the prevalence of eruptive vellus hair cysts (EVHCs)What are the racial predilections of eruptive vellus hair cysts (EVHCs)What are the sexual predilections of eruptive vellus hair cysts (EVHCs)At what age are eruptive vellus hair cysts (EVHCs) typically diagnosed?What is the prognosis of eruptive vellus hair cysts (EVHCs)?Which clinical history findings are characteristic of eruptive vellus hair cysts (EVHCs)?Which physical findings are characteristic of eruptive vellus hair cysts (EVHCs)?Which conditions are associated with eruptive vellus hair cysts (EVHCs)?What are the differential diagnoses for Eruptive Vellus Hair Cysts?How is a diagnosis of eruptive vellus hair cysts (EVHCs) confirmed?What is the role of dermoscopy in the workup of eruptive vellus hair cysts (EVHCs)?Which histologic findings are characteristic of eruptive vellus hair cysts (EVHCs)?How are eruptive vellus hair cysts (EVHCs) treated?What is the role of surgery in the treatment of eruptive vellus hair cysts (EVHCs)?What is the role of medications in the treatment of eruptive vellus hair cysts (EVHCs)?Which medications in the drug class Retinoid-like Agents are used in the treatment of Eruptive Vellus Hair Cysts?Which medications in the drug class Topical Skin Products are used in the treatment of Eruptive Vellus Hair Cysts?
Nicholas V Nguyen, MD, Director of Pediatric Dermatology, Akron Children's Hospital
Disclosure: Nothing to disclose.
Specialty Editors
Francisco Talavera, PharmD, PhD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference
Disclosure: Received salary from Medscape for employment. for: Medscape.
Edward F Chan, MD, Clinical Assistant Professor, Department of Dermatology, University of Pennsylvania School of Medicine
Disclosure: Nothing to disclose.
Chief Editor
Dirk M Elston, MD, Professor and Chairman, Department of Dermatology and Dermatologic Surgery, Medical University of South Carolina College of Medicine
Disclosure: Nothing to disclose.
Additional Contributors
Cory A Dunnick, MD, Associate Professor, Director of Contact Dermatitis Clinic, Director of Medical Student Education, Department of Dermatology, University of Colorado Denver School of Medicine
Disclosure: Nothing to disclose.
Harry Dao, Jr, MD, Assistant Professor, Department of Dermatology, Baylor College of Medicine
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