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Presentation

Acute Retiform Purpura: Differential Diagnosis, Evaluation, and Calciphylaxis Updates

Description

This talk reviewed acute retiform purpura, emphasizing how to distinguish non-inflammatory from inflammatory patterns to narrow the differential diagnosis and guide evaluation. Non-inflammatory causes included vascular occlusion from abnormal circulating blood, emboli, organisms, and thrombi, with examples such as type 1 cryoglobulinemia, cholesterol emboli, infective endocarditis, Rocky Mountain spotted fever, ecthyma gangrenosum, angioinvasive fungal infection, HIT, antiphospholipid syndrome, DIC, and protein C/S deficiency or warfarin necrosis. Inflammatory retiform purpura focused on vasculitis, especially the importance of vessel caliber and clinical clues such as palpable purpura, livedo racemosa, ulcers, nodules, and infarcts; levamisole-adulterated cocaine causing ANCA-associated vasculitis was highlighted. The evaluation approach was streamlined with targeted labs, cultures, serologies, imaging, and biopsy based on whether disease appeared inflammatory or not, plus specific red flags like fever, immunocompromise, eosinophilia, thrombocytopenia, renal disease, and cold-induced lesions. The disease in focus was calciphylaxis, reviewed as a painful, high-morbidity disorder with classic risk factors and morphology, while recent studies questioned the benefit of sodium thiosulfate and suggested promise for emerging targeted therapies such as SNF-472 and INZ701.

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Conclusions

Acute retiform purpura is best approached by first separating non-inflammatory from inflammatory patterns, because that classification narrows the differential diagnosis and workup substantially.
Non-inflammatory retiform purpura is usually due to vascular occlusion from abnormal circulating blood, emboli, organisms, or thrombi, and the key causes include cryoglobulinemia, cholesterol emboli, endocarditis, infection-related occlusion, HIT, DIC, APS, and protein C/S disorders.
Inflammatory retiform purpura points more toward vasculitis, with vessel caliber helping distinguish small-vessel, medium-vessel, and larger-vessel processes.
Skin exam and biopsy are highly informative in retiform purpura because the lesion morphology and depth of inflammation can reflect the size and type of affected vessel.
Red-flag clinical features such as fever, immunocompromise, hyper-eosinophilia, thrombocytopenia, cold-induced lesions, renal disease, or cocaine exposure should direct targeted testing and help avoid an overly broad evaluation.
Calciphylaxis remains a critical cause of painful non-inflammatory retiform purpura, especially in patients with kidney disease and other mineral-metabolism risk factors.
The classic teaching that intravenous sodium thiosulfate is clearly effective for calciphylaxis is being questioned by newer cohort data showing no clear improvement in lesion healing or survival.
Newer calciphylaxis therapies such as SNF472 and INZ-701 are promising because they directly target vascular calcification, although definitive clinical benefit is still unproven or incomplete.
Overall, careful clinical pattern recognition, focused laboratory testing, and timely biopsy can streamline evaluation of retiform purpura and improve diagnostic accuracy.
The field of calciphylaxis management may be shifting away from dogma toward more targeted, mechanism-based therapies.

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