Patient: Male, 64Final Diagnosis: Collapsing focal segmental glomerulosclerosis with acute interstitial nephritis associated with Plasmodium falciparumSymptoms: Diarrhea • chills • fever • myalgiaMedication: —Clinical Procedure: —Specialty: NephrologyObjective:Muhammad Azhar, e-mail: mazhar@bhmcny.orgBackground:Malaria adversely affects the kidney in a variety of ways. The most common kidney injury is acute tubular necrosis, although various glomerular lesions are also described. Of these, collapsing focal segmental glomerulo-sclerosis (cFSGS) is the most rarely seen. Thus, the natural history of this lesion and response to treatment are not clear. Herein, we present a case of cFSGS complicated by acute interstitial nephritis caused by Plasmodium falciparum (P. falciparum) unresponsive to prednisone.Case Report:A 64-year-old Nigerian man with chronic kidney disease due to hypertensive nephropathy was admitted to the hospital, diagnosed with active P. falciparum malaria infection after returning from Nigeria. He developed acute kidney injury and nephrotic range proteinuria. Renal biopsy showed acute interstitial nephritis and cFSGS. Despite corticosteroid therapy, his kidney function worsened, requiring initiation of renal replacement therapy. This is the fifth case report of cFSGS due to malaria P. falciparum but the first to report the presence of acute interstitial nephritis in association with cFSGS due to malaria.Conclusions:cFSGS is rarely seen as a manifestation of P. falciparum infection. When associated with acute interstitial nephritis, the prognosis seems to be worse. It appears that age and co-morbidities are the risk factors for unresponsiveness to corticosteroids, and treatment of the renal disease should focus on rapidly eradicating the parasitemia and providing supportive care. Our case report is the first to describe a combination of cFSGS and interstitial nephritis caused by P. falciparum unresponsive to corticosteroids.