Proteinuria in obesity: ORG or FSGS?

Clinical stem

A 46-year-old with class III obesity, no diabetes, eGFR 78, serum albumin normal, and 3.5 g/day proteinuria — but no edema and no other nephrotic features.

The trap

Heavy proteinuria triggers a reflex diagnosis of primary FSGS or nephrotic syndrome and a move toward immunosuppression. Yet heavy proteinuria that behaves sub-nephrotically — preserved albumin, little or no edema — is characteristic of obesity-related glomerulopathy (ORG).

Diagnostic reasoning

ORG is a secondary, adaptive (perihilar) FSGS driven by glomerular hyperfiltration and glomerulomegaly. On electron microscopy, foot-process effacement is segmental and mild, unlike the diffuse effacement of primary FSGS. Proteinuria can be heavy, but the patient is rarely frankly nephrotic and the course is more indolent.

Safety pearl

Getting the distinction right redirects therapy: ORG is treated with weight loss, RAAS blockade, and SGLT2 inhibition — not corticosteroids or immunosuppression. When in doubt, biopsy (glomerulomegaly, perihilar FSGS lesion, mild effacement) resolves it.

What not to overclaim

Histologic features overlap, and ORG can coexist with other lesions; the clinical pattern is suggestive, not pathognomonic. Individualize, and biopsy when the picture is atypical.