Rare Case of Dual Pathology: Methamphetamine-Associated Acute Interstitial Nephritis and HIV/Hepatitis C Virus-Associated Fibrillary Glomerulonephritis

Introduction: Intravenous methamphetamine use has been rarely associated with acute interstitial nephritis (AIN). Hepatitis C virus (HCV) and human immunodeficiency virus (HIV) infections have been linked to fibrillary glomerulonephritis (fibrill-GN). However, coincidental presentation of those two entities has not been reported. We present a complex case of suspected methamphetamine-associated AIN coexisting with HCV/HIV-associated fibrill-GN. Case Description: A 45-year-old man, active IV drug abuse (IVDA) (methamphetamine and heroin), with uncontrolled HCV and HIV infections, was found unresponsive at a gas station. He was hypothermic and hypotensive. Empiric broad-spectrum antibiotics and pressors were initiated; cultures later grew Pseudomonas aeruginosa and Streptococcus viridans. Initial labs showed BUN 155 mg/dL and creatinine 7.7 mg/dL. CPK was normal. Urinalysis revealed >100 WBCs/hpf, 12 RBCs/hpf, and urine protein-to- creatinine ratio 1.62 g/g. No casts or dysmorphic RBCs were noted. HIV and HCV viral loads were 8,983 copies/mL and >12 million IU/mL, respectively. Complement levels were normal and cryoglobulins were negative. Renal US revealed nephromegaly. His renal function worsened, necessitating dialysis. A kidney biopsy was performed and it revealed AIN, acute tubular injury and glomeruli with mesangial moth-eaten expansion by light microscopy. Smudgy mesangial IgG by IF. Glomeruli were positive for DNAJB9 by IHC. Electron microscopy showed randomly arranged fibrils averaging 20 nm in the mesangium, all consistent with fibrill-GN. The patient received a 2-week course of 20 mg oral prednisone. Antiviral therapies (bictegravir/emtricitabine/tenofovir and glecaprevir/pibrentasvir) were initiated. Further immunosuppression was withheld due to active infections and high viral loads. He remains dialysis-dependent and was recently re-hospitalized for infectious endocarditis with septic emboli. Discussion: Given no prior exposure to antibiotics or NSAIDs, we attribute AIN to methamphetamine use. Fibrill-GN is likely related to HCV ± HIV. His IVDA status could be linked to both methamphetamine AIN and HCV/HIV-related GN. This case highlights the diagnostic and therapeutic challenges in patients with dual renal pathology and coexisting infections.