Acral steatocystoma multiplex

Sir,

Steatocystoma multiplex (SM) is a hamartomatous malformation of the pilosebaceous duct junction.[1] It is a distinct condition characterized by numerous small, skin-colored or yellowish, cutaneous cysts. SM can appear anywhere on the body but is more common in areas where the pilosebaceous apparatus is well developed such as the trunk, neck, axilla, inguinal region, scalp and the proximal extremities.[2] Acral SM is a rare condition and has been described in only three reports.[1–3]

A 35-year-old female presented to the dermatology OPD with multiple nodules in the left foot present for the duration of 1 year [Figure 1]. The lesions varied in size from 0.8 cm to 3.5 cm in diameter, were mobile, smooth and nontender. No punctum was present. There were no such lesions on the other parts of the body. The nails, teeth and hair were normal. The patient's past and family histories were noncontributory and the results of routine laboratory findings were within normal limits. Clinically, the differential diagnosis of eruptive vellus hair cyst, lipoma, epidermal cyst and steatocystoma multiplex were kept and a punch biopsy was performed to confirm the suspected diagnosis. Histopathology showed unremarkable epidermis with numerous cysts of variable sizes in the dermis [Figure 2]. Underlying subcutaneous tissue also showed similar cysts. The cyst was lined by flattened to stratified squamous epithelium along with presence of sebocytes in the wall. Sebaceous gland lobules as well as individual cells were seen within or close to the wall [Figure 3]. A foreign body giant cell reaction was also seen around the cyst. From these findings, the diagnosis of SM was finally made.

Figure 1.

Multiple mobile nodules in the left foot

Figure 2.

Histopathology showing unremarkable epidermis with numerous cysts of variable sizes in the dermis. (H and E, ×100)

Figure 3.

Histopathology showing sebaceous gland lobules as well as individual cells close to the cyst wall. (H and E, ×400)

Steatocystoma multiplex is usually hereditary and it is inherited as an autosomal-dominant disorder; however, in some cases, no familial pattern can be established. Steatocystomas are now recognized as a nevoid or hamartomatous malformation of the pilosebaceous junction. The causative factors of steatocystoma multiplex remain unclear; yet, Setoyama et al. suggested that trauma, infection or immunological events might be responsible.[4] The clinical differential diagnosis of steatocystoma multiplex includes multiple epidermoid cysts, eruptive vellus hair cyst, neurofibromatosis, lipomas and xanthomatosis. A skin biopsy specimen from a representative lesion is diagnostic. The reason why our case exhibited an acral distribution is not understood, but a combination of ectopic sebaceous follicles and possible keratin defect along with environmental factors may be involved in this unique clinical appearance.