Pruritic bluish-black subcutaneous papules on the chest
Published Web Locationhttps://doi.org/10.5070/D392w5x3b7
Pruritic bluish-black subcutaneous papules on the chest1. College of Physicians & Surgeons, Columbia University, New York, NY 2. Department of Dermatology, University of California,
Irvine, Irvine, CA. firstname.lastname@example.org 3. Department of Dermatology, University of California, San Francisco, San Francisco,
CA; and Palo Alto Foundation Medical Group, Mountain View, CA
Vivian T Laquer BS1, Jashin J Wu MD2, Joshua A Tournas MD2, Jenny E Murase MD3, Senait W Dyson MD2
Dermatology Online Journal 14 (3): 14
Steatocystoma multiplex (SM) is characterized by multiple dermal cysts involving the pilosebaceous glands. Although most presenting cases are sporadic, there is a rare familial syndrome involving a mutation in keratin 17 (K17) that is inherited in an autosomal dominant fashion. SM often presents concomitantly with eruptive vellus hair cysts (EHVS) and pachyonychia congenital type 2 (PC-2). We report a sporadic case of SM in a 21-year-old man.
Steatocystoma multiplex (SM) is a rare syndrome characterized by benign nevoid sebaceous gland tumors , which usually occur predominantly on the neck, chest, arms, and axillae . There has not been evidence of a gender or ethnic predilection. Most cases are sporadic and present in adolescence to early adulthood , but some familial cases with mutations in keratin 17 (K17) have been reported and are inherited in an autosomal dominant fashion .
A 21-year-old male presented with a 1-year history of multiple dark bumps on his chest and abdomen since his deployment to Kuwait. These lesions were itchy and became worse in hot climates but did not worsen in cooler temperatures. An allergic reaction to his dog tag necklace was deemed less likely because the affected area persisted and grew larger after removal of the presumed antigen. Treatment with over-the-counter acne medications did not help.
|Figure 1. Grossly, the lesions appear as bluish-black subcutaneous papules in clusters on the anterior wall of the chest.|
Physical examination revealed multiple bluish-black superficial and deep subcutaneous papules in clusters on the chest (Fig. 1). The clinical differential diagnosis was comedonal acne and SM. A biopsy specimen showed cyst without cyst contents and sebaceous glands within and close to the cyst wall (Fig. 2). The cyst wall was composed of stratified squamous epithelium without a granular layer, and a thick, homogenous, eosinophilic layer protruding towards the cyst lumen (Fig. 3).
In SM, the pilosebaceous unit overproduces vellus hairs that become trapped in a cystic cavity. This cyst then fills with cellular debris from the surrounding tissues and forms the visible bumps classically seen on physical examination  Lesions are generally benign and treatment is primarily for cosmetic purposes . Due to the tendency of the cysts to spontaneously rupture and scar, SM is often confused with acne conglobata .
Pachyonychia congenital type 2 (PC-2) is also an autosomal dominant disorder with the same mutation in K17 with a different clinical presentation . Patients present with hyperkeratosis of nails, palmoplantar keratosis, follicular keratosis, oral leukokeratosis, bullae of palms and soles, palmar and plantar hyperhidrosis, natal or neonatal teeth, and steatocystoma multiplex . It is postulated that SM may only be one manifestation or a variant of PC-2 because they both have the same underlying etiology .
Eruptive vellus hair cysts (EVHC) have also been known to be present concurrently with steatocystoma . EVHCs appear as asymptomatic papules either in groups or scattered across the anterior chest or extremities. EVHC and SM both have similar clinical features, but their histology differs significantly. Whereas the cyst walls of SM show eosinophilic cuticles lacking a granular layer and display remnants of sebaceous tissue, EVHCs are lined with mature squamous cells with a granular layer and are not associated with sebaceous glands .
On histopathology, SM is characterized by an eosinophilic cuticle lacking a granular layer. The cystic cavity is sometimes filled with vellus hairs and hair follicles . Grossly, the contents of the cysts appear oily .
The current treatment for SM includes oral therapy and surgical intervention. Mini-incision with drainage of contents appears to be an effective permanent treatment for an individual cyst already present . Administration of oral isotretinoins has been shown to cause regression of the lesions , but the preferred method of treatment still remains controversial.
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