A 36-year-old factory worker developed itchy,annular scaly plaques in both groins. Application of a coicosteroid ointment led to temporary relief but the plaques continued to extend at the periphery.The most likely diagnosis is

Erythema annulare centrifugum (EAC) Epidemiology :- * Peaks in fifth decade Pathogenesis:- * Unknown, but may be an immune reaction to an antigen such as infection (e.g., tinea pedis, other dermatophyte infections, other fungi, viruses, and parasites), drug, pregnancy, and neoplasms (usually lymphoproliferative malignancies) Clinical features :- * Sta as firm pink papule - erythematous annular lesions that migrate centrifugally (outward; up to 6 cm diameter in 2 weeks). * Trailing scale (inner margin desquamation) is common in superficial lesions, but not deep lesions. * Most commonly on thighs/hips, but can become more generalized. Histopathology :- * Superficial EAC: mild spongiosis, focal parakeratosis, and perivascular lymphohistiocytic infiltration, which is tight and dense ("coat sleeve") * Deep EAC: deep and tight perivascular lymphohistiocytic inflammation Treatment :- * Treat underlying disorder if present; otherwise topical steroids Prognosis/clinical course :- * Lesions last days to month. Ref:- Review of Dermatology by Alikhan; pg num:-148