Abstract

Kaposi sarcoma (KS), neoplasm of the endothelial cells, has a well-established association with immune deficiency/dysregulation (IDD), namely HIV-infection. The four recognized clinico-epidemiologic KS subtypes include classic, endemic, epidemic, and iatrogenic forms. With increasing incidence, an emerging fifth subtype is recognized that describes non-epidemic KS in men who have sex with men (MSM) who are HIV-negative and without underlying IDD. We describe a 58-year-old HIV-negative MSM male who presents with asymptomatic but extensive rash for one year. On initial visit, the rash features faint, ill-defined, erythematous red-brown, non-scaly, and slightly elevated plaques on his left lower flank, left lower abdomen, and bilateral thigh with clusters of violaceous thin papules on bilateral medial calves. Biopsy shows superficial perivascular dermatitis that are negative for bacterial, fungal, and acid-fast-bacillus studies on histology and tissue culture. Topical steroids followed by antifungal are started with no improvement. Four months later, the rash becomes vascular with a purpuric appearance and surrounding halo, clinically resembling KS. Human herpesvirus-8 (HHV-8) immunostain is added on the initial biopsy showing sparse positivity of the endothelial cells, consistent with KS. This form of KS suggests that risk factors such as age, sexual behavior, and genetic predisposition contribute to the development of KS. Certain sexually transmitted infections, such as HHV-8 and syphilis, also play a role in the development of KS in this population. Though this KS subtype is indolent with favorable outcomes, its recognition is important for identifying the group individuals at increased risk for KS.