Abstract
Granuloma annulare (GA) is an idiopathic dermatosis characterized by one or more erythematous papules that form annular plaques on the extremities. The generalized variant is the most common clinical pattern reported in patients with human immunodeficiency virus (HIV) infection. Histopathologically, a dermal histiocytic infiltrate with altered collagen and increased mucin is seen. Kaposi sarcoma (KS) is a HHV-8 induced vascular neoplasm . In the HIV-associated type, early patch stage lesions are bruise-like macules or patches often on the trunk, arms or head and neck. Histopathologically, early lesions show a dermal proliferation of thin-walled vessels associated with red blood cell extravasation and hemosiderin deposition. Here we describe a unique case of a 60-year-old HIV positive man with GA of the lower extremities masking underlying KS. The patient presented with a two-year history of patches on his right anterior-medial shin. A punch biopsy revealed an interstitial histiocytic infiltrate with increased dermal mucin consistent with GA. Additionally there were increased dermal blood vessels and hemosiderin deposition favored to represent stasis changes based on the anatomic location. Given the patient’s history of HIV infection, a HHV-8 immunohistochemical stain was performed and was positive in the dermal vessels, confirming a diagnosis of KS. Both GA and KS are associated with HIV infection and can have similar presentations. In this case, the anatomic location and dermal histiocytic infiltrate with mucin made the vascular proliferation of KS difficult to identify. Given the proper clinical setting, patients with suspected GA should also be investigated for a masked KS.