Allopurinol induced granuloma annulare in a patient of lepromatous leprosy
Seventy year old male presented with multiple aymptomatic red raised lesions over back for one month. He was a known case of lepromatous leprosy and was on multidrug therapy for multi bacillary Hansen's disease for the past six months. There was past history of intake of allopurinol for hyperuricemia which was started one year back. There was history of similar lesions six months back which healed within one month of stopping allopurinol and he started taking the drug for the past four months on his own without any medical advice. There was no history of any other drug intake and any other associated systemic illness. On examination, there were multiple grouped but discrete, annular, firm, non tender, smooth surfaced skin colored papular lesions ranging in size from 0.5-1 cm over back [Figure and ]. There was diffuse loss of touch and temperature sensations over dorsal aspect of bilateral hands and feet, with thickening of bilateral ulnar and common peroneal nerves. There was ulnar clawing in bilateral hands and blister over index finger of right hand. Based on history and clinical examination, differential diagnosis for the lesions over back included granuloma annulare (drug induced), lesions of lepromatous leprosy, sarcoidosis. On routine investigations, complete blood counts, liver and renal function tests, thyroid function tests, random blood sugar, chest radiographs were within normal limits. Enzyme linked immunosorbent assay for human immunodeficiency virus 1 and 2 was non reactive. Histo-pathological examination of biopsy sample from lesion over back showed sparse superficial and deep perivascular lymphocytic infiltrate with numerous histiocytes scattered in the intersititum of reticular dermis. Abundant mucin was present in between the histiocytes. The overlying epidermis was unaffected []. Thus the diagnosis of generalised interstitial granuloma annulare was confirmed. As allopurinol has previously been implicated as an etiological agent in granuloma annulare, the patient was advised to stop the drug in future. The patient was reviewed after a period of fourweeks, the lesions of granuloma annulare over his back had completely resolved [Figure and ]. Naranjo's algorithm was also applied for determination of adverse drug reaction probability and the total calculated score was 6, which showed a probable association. Thus the diagnosis of allopurinol induced generalised interstitial granuloma annulare was confirmed. The patient was advised to continue with the antileprotic drugs, low purine diet and to avoid allopurinol intake.