Kidney Biopsy in a Patient with Cardiorenal Metabolic Syndrome—How to Interpret Histopathology

The components of Cardiorenal Metabolic Syndrome (CRMS) include central obesity, insulin resistance, hypertension, metabolic dyslipidemia, proteinuria, and/or reduced glomerular filtration rate. Kidney biopsy is rarely performed in patients with CRMS; histopathology findings include glomerulopathy, podocytopathy, mesangial expansion and proliferation, glomerular basement thickening, global and segmental sclerosis, interstitial fibrosis and tubular atrophy, and arterial sclerosis and hyalinosis. We report a case of CRMS with slow progression during 10 years of follow-up on chronic kidney disease (CKD). The middle-aged patient had central obesity, hypertension, dyslipidemia, cardiovascular disease, type 2 diabetes mellitus, proteinuria, and CKD stage G3b-G4. Kidney biopsy, performed 3 years after the first presentation, led to the diagnosis of chronic thrombotic microangiopathy (TMA) and complement-associated glomerulopathy. This was not compatible with the medical history and the course of the disease, and previous kidney biopsy review showed metabolic nephropathy with glomerulomegaly, global and segmental glomerulosclerosis, tubular atrophy and interstitial fibrosis, arteriosclerosis, and lipid embolus in the lumen of one artery, and found neither TMA features nor C3 deposition. The reported case demonstrates the importance of an accurate and thoughtful reading and interpretation of kidney biopsy, and stresses that disregarding medical history may potentially mislead and alter the understanding of the true cause of CKD.