Tubulointerstitial Nephritis and Mesangial Proliferative Glomerulonephritis: A Rare Initial Presentation of HIV Infection

Introduction: HIV infection is a wide-spread disease that is associated with a myriad of renal manifestations. The classic renal pattern of injury is collapsing FSGS; know as HIVAN. Other glomerular entities have also been recognized, such as HIV-associated immune complex kidney disease and Membranous nephropathy. Tubulo-interstitial damage can also occur, such as proximal tubule injury, chronic tubular injury, and interstitial nephritis, albeit these entities have been largely associated with drug toxicity from ART. We present a case of newly diagnosed HIV infection without AIDS and a rare pattern of renal injury. Case Description: A 26 yo M with no known PMH presented with complaints of tunnel vision and tachycardia for 2 weeks. He also mentioned unintentional weight loss of 20–30 lbs in a year. He was found to have a hemoglobin of 5.5 g/dL and creatinine of 2.4 mg/dL (unknown baseline). Hemolytic work up was negative. Urine microscopy showed hyaline casts and numerous RBCs. Laboratory evaluation demonstrated a MACR of 234 mg/g and a PCR of 1.4 g/g. C3 was normal and C4 was <8 mg/dL, with negative ANA, ANCA, and anti-GBM serologies. Cryoglobulins, Hepatitis B and C serologies were negative, but HIV-1 testing returned positive. His CD4 count was 333 cells/μL and viral load was 168,000 copies/mL. Renal biopsy revealed acute and chronic injury characterized by glomerular immune injury with a mesangial pattern, podocyte injury with focal global glomerulosclerosis (23%), and tubulointerstitial nephritis with areas of mononuclear infiltrate and acute tubular injury. No definitive glomerular endothelial TRIs were identified as well. The patient's creatinine had stabilized at 1.8 to 2.0 mg/dL for 2 weeks prior to ART initiation. Afterwards, his renal function showed gradual improvement, with a creatinine of 1.5 mg/dL 6 weeks after starting therapy. Discussion: The optimal therapeutic approach for tubulointerstitial nephritis and MesPGN in the context of HIV infection remains unclear. The underlying pathophysiology and natural history of these entities are still under investigation. However, in ART-naïve patients with stable renal function, initiation of ART is generally favored as the initial intervention. In this case, our patient exhibited an acceptable improvement in renal function within a few weeks of starting ART, without the need for adjunctive corticosteroid therapy.