Retiform purpura

What?

• purpura = local extravasation of RBCs (hemorrhagic skin lesions)

• retiform = angulated or branched appearance; the shape reflects the vascular architecture in the skin

• pain within lesions is common and may be severe

• skin necrosis results from infarction

Purpura fulminans: widespread retiform purpura, can be a life-threatening condition

Ddx from Livedo reticularis, Livedo racemosa - nonpurpuric disorders that present with accentuated vascular patterns in the skin

Why? as a consequence of complete vascular occlusion or vascular damage involving blood vessels in the skin

• Vessel occlusion: thrombosis, emboli, or intravascular protein deposition

• Thrombosis: DIC, hypercoagulable states (Antiphospholipid sydrome, ATIII deficiency, protein C/S deficiency, prothrombin III mutation, factor V Leiden, hyperhomocysteinemia), TTP, warfarin-induced skin necrosis, HIT, PNH

• Intravascular protein deposition: cryoglobulinemia (type 1), cryofrinogenemia, paraproteinemia

• Emboli: cholesterol emboli (+eosinophilia), septic emboli, atrial myxoma, nonbacterial thrombotic endocarditis (maratic endocarditis, Libman-Sacks), hypereosinophilic syndrome

• Vessel wall destruction: vasculitis, calciphylaxis, some severe opportunistic infections

• Vasculitis: medium-vessel, inflammatory infiltrate invading blood vessel walls and fibrinoid necrosis (fibrin deposition within vessel walls or lumina)

  vs. small vessel vasculitis -> nonretiform palpable purpura

• Septic vasculitis: meningococcal/gonococcal/pseudomonal/streptococcal septicemia, rickettsial infections, infective endocarditis, etc, +/- DIC

• Vasculitis: autoimmune disease or primary systemic vasculitis - RA, SLE, PAN, GPA, EGPA

• Cryoglobulinemic vasculitis (cryoglobulinemia types 2 and 3)

• Opportunistic infections

• Bacterial: pseudomonal infection (ecthyma gangrenosum), lepromatous leprosy (Lucio phenomenon)

• Fungal: invasive fungal infections (eg, mucormycosis, aspergillosis, candidiasis)

• Parasitic: disseminated strongyloidiasis

• Calciphylaxis

• Primary hyperoxaluria (AR metbolic disorder -> oxalate excesss -> renal stone, calcium oxalate deposits in tissues including blood vessels)

• Others

• Livedoid vasculopathy (fibrin thrombi in cutaneous vessels -> recurrent, small, purpuric, ulcerative lesions on the distal lower extremities)

• Pyoderma gangrenosum

• Thrombotic vasculopathy or vasculitis due to levamisole-contaminated cocaine