A Complex Case of Unilateral Stasis Dermatitis With Id Reaction Misdiagnosed as Cellulitis: A Diagnostic Challenge.

Autoeczematization, or id reaction, is a secondary eczematous eruption occurring at sites distant from a primary inflammatory skin process. It is often underrecognized in patients with stasis dermatitis and can mimic cellulitis or drug-induced eruptions. A male in his 50s with plaque psoriasis and a history of heavy smoking (55 pack years) presented with acute unilateral left leg erythema and edema, initially treated as recurrent cellulitis. He subsequently developed a diffuse, pruritic morbilliform eruption on the trunk and extremities. Biopsies revealed chronic spongiotic dermatitis in the leg and nonspecific spongiotic changes in the trunk. Imaging and cultures excluded infection or abscess. The eruption was diagnosed as autoeczematization secondary to stasis dermatitis. Topical corticosteroids, compression therapy, leg elevation, and skin care led to the gradual resolution of both local and widespread lesions. Clinicians should consider venous stasis in cases of unilateral leg swelling and recognize autoeczematization as a potential complication. Timely and accurate diagnosis can prevent unnecessary systemic therapies, with management focused on compression, topical corticosteroids, and supportive skin care.