Track

Abstract

A 38-year-old woman with a history of Adult-onset Still’s Disease (AoSD) complicated by hemophagocytic lymphohistiocytosis (HLH) and macrophage activation syndrome (MAS) was admitted for a disease flare. She had recently transitioned from anakinra to canakinumab due to generalized pruritus. Two weeks into hospitalization, dermatology was consulted for a new rash on the dorsal aspects of the hands and feet. Physical examination revealed ill-defined violaceous patches with areas of retiform purpura, concerning for vasculitis/coagulopathy. A punch biopsy demonstrated a dermal medium-caliber vessel with an intraluminal fibrin thrombus and associated CD163-positive histiocytes. The histiocytes did not show engulfment of hematolymphoid cells in multiple examined levels. No active vasculitis, perivascular inflammation, dermal histiocytic infiltrate, or superficial epidermal dyskeratotic keratinocytes were noted. The findings were consistent with a coagulopathic process. The patient subsequently expired due to intracranial hemorrhage. MAS is a life-threatening complication of systemic autoinflammatory diseases like AoSD, marked by uncontrolled macrophage and T-cell activation. Cutaneous findings in MAS include coagulopathy, generalized erythematous salmon-colored macular/maculopapular rash, atypical persistent pruritic eruptions such as dermatomyositis-like rashes, periorbital erythema, heliotrope-like lesions, and linear flagellate papules and plaques, or purpuric or annular papules and plaques. However, dermatopathology findings in MAS-associated eruptions are uncommonly reported. We describe the presence of an intravascular fibrin thrombus with associated intraluminal histiocytes, without pathologic features of vasculitis or HLH, in the setting of MAS; a feature that may reflect underlying immune dysregulation and vascular injury. Recognizing this pattern may offer additional diagnostic insight and expand the known spectrum of MAS-associated cutaneous manifestations.