Erythema Nodosum Leprosum as a Rare and Challenging Cause of Pyrexia of Unknown Origin.

A 30-year old male presented with fever for last 1 year. There were associated multiple painful skin eruptions with hyperpigmentation and scaling over whole body which had been progressively increasing. He also had anasarca along with generalized weakness. He presented to us in shock after an acute episode of gastroenteritis. After stabilization, he was evaluated for cause of fever. Routine fever workup (for typhoid, syphilis, malaria, filariasis, HIV, scrub typhus, leishmaniasis) was negative. CECT chest and abdomen revealed hepatosplenomegaly. There was no response to intravenous (IV) antibiotics and anti-fungal medications. Slit skin smears revealed 3+ acid fast bacilli (AFB). Skin biopsy revealed fragmented acid-fast bacilli with dense collection of neutrophils and foamy histiocytes in upper and middle dermis suggestive of Erythema Nodosum Leprosum (ENL). A diagnosis of ENL with lepromatous leprosy was made and patient started on steroids and thalidomide and subsequently on multidrug therapy (MDT). On therapy, patient's symptoms improved, and skin lesions resolved. Though Leprosy itself is a well-known common cause of PUO in India, its first presentation as ENL is rare and needs good index of suspicion and timely management.