An 84-year-old man presenting with febrile cytopenia and acute glomerular disease. Lessons for the Clinical Nephrologist

An 84-year-old man with aortic dilatation, chronic obstructive ­pulmonary disease, asthma, and recurrent respiratory infections ­presented with a five-month history of fever of unknown origin, asthenia, moderate weight loss, and progressive dyspnea. Administration of several antibiotic and corticosteroid regi­mens had been unsuccessful. Computed tomography (CT) scans revealed splenomegaly and bilateral pleural effusion, but no ­lymphadenopathy or parenchymal lesions. Initial laboratory tests showed anemia (7.4 g/dL), thrombocytopenia (66 G/L), marked inflammation (C-reactive protein [CRP] 82 mg/L; ferritin 2520 µg/L), elevated lactate dehydrogenase (LDH) (620–888 U/L), and hypoalbuminemia (21 g/L). Renal assessment showed acute kidney disease with signs of glomerular involvement: creatinine 139 µmol/L, proteinuria 1.1 g/g (64% albumin), and microscopic hematuria. Serum protein electrophoresis detected a monoclonal IgG kappa spike. Immunological testing (anti-nuclear antibody [ANA], antineutrophil cytoplasmic antibody [ANCA], antiphospholipid antibodies, C3/C4, UBA1 gene, ADAMTS13 activity) was unremarkable. Viral polymerase chain reactions (PCRs) (EBV, HHV-8, Parvovirus B19), beta-D-glucan testing, and repeated hemocultures were negative. Urine microscopy revealed dysmorphic erythrocytes without casts.