Background The disorders associated with metabolic syndrome (MS) can lead to renal disease. IgA nephropathy is the most common form of glomerulonephritis, and many patients with this disorder progress to renal failure.

Aims To identify the effect of MS on IgA nephropathy by retrospectively comparing patients who had IgA nephropathy and MS with those who had IgA nephropathy alone.

Methods 30 patients with MS and IgA nephropathy (MS group), and 30 matched controls with IgA nephropathy alone (non-MS group) were enrolled. IgA nephropathy was diagnosed by renal biopsy; activity and severity was graded by two classification systems. MS was diagnosed by criteria of the Diabetes Society of the Chinese Medical Association.

Results Simple and multiple linear regression models (which adjusted for age, gender and body surface area) showed that only hypertension significantly affected serum creatinine, an indicator of the clinical severity of renal disease. Simple and multiple linear regression models (which adjusted for age, gender and body surface area) also showed that hypertensive patients had higher Katafuchi scores, an indicator of the pathological severity of renal disease.

Conclusion Among the disorders associated with MS, hypertension is the most important factor for renal disease.