A 24 year old man presents with a non-productive cough and worsening exertional dyspnea for 1 month, associated with intermittent chills and night sweats.

He was treated with Roxithromycin + Amoxicillin for 2 weeks, with no response.

His basic investigations are significant for an Hb of 6.0 g/dL with normal leukocyte and platelet counts, and a serum creatinine of 1.6 mg/dL, with an eGFR of 30 ml/min/1.73m2.

A CXR shows pulmonary infiltrates in the lower regions of both lungs; a urinalysis shows microscopic hematuria with erythrocyte casts.