Unknown Disease or Unusual Mesoamerican Nephropathy?

Introduction: Mesoamerican Nephropathy (MeN) is a known disease in patients from Central and North America with history in manual labor industries. Aside from ruling out HTN, DM, and AKI, diagnosis requires GFR below 60 ml/min, urine P/C ratio below 2, biopsy showing tubular atrophy, fibrosis, and glomerulosclerosis. We had a patient with nephrotic proteinuria and biopsy consistent with MeN. Whether the proteinuria indicated an unknown disease or an unsual case of MeN is an area of uncertainty. Case Description: A 31-year-old male with no past medical history was hospitalized after routine labs showed creatinine of 3.9 mg/dL and bicarbonate of 17 mmol/L. He recently moved from Mexico and spent years working in the textile industry. He denied any other symptoms. Vitals were 135/74 mmHg, 72 bpm, 15, 98.6 F and 98%. Exam was non-revealing. CT and ultrasound were negative for obstruction, revealing increased renal cortical echogenicity. Urine studies showed intrinsic disease, and proteinuria with P/C ratio of 3.7. Workup for autoimmune disease, vasculitis, diabetes, and infection were negative. He was initiated on bicarbonate supplementation, and creatinine improved the day after to 3.6 mg/dL; acidosis resolved. He was discharged with renal biopsy scheduled outpatient, which later showed diffuse tubulointerstitial fibrosis with atrophy and global glomerulosclerosis (Figure 1). He was scheduled to see nephrology outpatient. Discussion: Our patient presented with a picture consistent with MeN despite proteinuria above the maximum level for diagnosis. His history in the textile industry suggests exposure to silica. It is unclear whether this may have resulted in a variant of MeN, or if he had another unknown disease. Atypical presentations of renal disease associated with occupational exposures demand further attention.