An unusual cause of hypertension with hematuria and proteinuria: Answers

The renal biopsy shows diffuse glomerular basement membrane duplication (“track-tracking”) (Fig. 1a, b, arrowheads), mild mesangial hypercellularity, and mesangial sclerosis alternating with areas of mesangiolysis (Fig. 1c). Five of 43 glomeruli show segmental sclerosis lesions (Fig. 1d). Arterioles show mild to moderate intimal hyalinosis (Fig. 1e). Immunofluorescence stains (not shown) display segmental glomerular tuft staining for immunoglobulin (Ig)M and C3 in areas of sclerosis, and no staining for IgG, IgA, C1, fibrin/fibrinogen, or kappa or lambda light chains. Electron microscopy reveals diffuse glomerular basement membrane duplication with segmental mesangial interposition and endothelial cell swelling with focal loss of fenestrations (Fig. 1f). These findings are consistent with chronic thrombotic microangiopathy (TMA).

Cobalamin (Cbl) G disorder (methionine synthase deficiency)

Management consists of angiotensin-converting enzyme (ACE) inhibition therapy to treat both hypertension and proteinuria, with optimization of vitamin B12 and folinic acid supplements to achieve the goal of decreasing serum homocysteine levels. The patient was started on lisinopril following the renal biopsy, and the urine protein:creatinine ratio fell from 3.8 to 0.35 g/g in 9 months. At 12 months’ follow-up, urinalysis revealed no protein, and serum creatinine was 0.46 mg/dl.