Background Anti-glomerular basement membrane (GBM) disease and ANCA-associated vasculitis (AAV) diseases are rare. It is associated with variable renal manifestations and increased mortality, thus requiring early aggressive treatment to minimize adverse outcomes and improve prognosis. Case presentation We present the case of a male patient with 1-month onset of asthenia, adynamia, oliguria, and weight loss. Initial laboratory findings were indicative of severe kidney dysfunction. The urinalysis showed active sediment, but the urinary tract ultrasound was unaltered. As these findings were consistent with rapidly progressive glomerulonephritis, he received steroid pulses, and given the severity of the condition, renal replacement therapy was initiated. Other diagnostic tests revealed MPO-ANCA antibody levels of 26 mg/dl, pANCAs 1/320, and anti-GBM of 8 mg/dl. Kidney biopsy evidenced necrotizing glomerulonephritis with extracapillary proliferation in 90% of the glomeruli. The patient received plasma exchange (PE) therapy and intravenous (IV) cyclophosphamide (CYC) cycles; however, he presented with severe alveolar hemorrhage requiring the completion of 21 PE sessions and 3 CYC boluses. Pulmonary symptoms resolved, but the patient persisted dependent on dialysis. During the outpatient follow-up, monthly CYC were prescribed until circulating antibody levels were normal; however, the patient did not recover full kidney function and remained dependent on renal support. Conclusions Anti-GBM and AAV diseases are rare; therefore, anti-GBM antibodies should be screened simultaneously in patients with ANCA positive, especially in older patients, due to the early morbidity and mortality typical of anti-GBM disease with comparable disease severity it represents.

La enfermedad de cambios mínimos (ECM) es la principal causa de síndrome nefrótico en niños y una causa poco común en adultos, asociándose usualmente a causas secundarias; predominantemente de origen hematológico. Es poco frecuente que este tipo de glomerulopatía se diagnostique de manera sincrónica en pacientes con tumores sólidos. Presentamos el caso de un paciente de 35 años con diagnostico reciente de cáncer de recto quien ingresa con un cuadro compatible con síndrome nefrótico, a quien se diagnostica en la biopsia renal una enfermedad de cambios mínimos, con mejoría parcial del cuadro posterior al manejo quirúrgico de la patología neoplásica. Consideramos que este caso puede ser útil en el enfoque diagnóstico y el manejo de pacientes que presenten tumores sólidos de origen gastrointestinal con síndrome nefrótico concomitante.