Idiopathic nodular glomerulosclerosis in a never-smoking, normotensive, non-obese, normal-glucose-tolerant middle-aged woman

A 53-year-old woman with a history of dyslipidemia presented with medium-grade proteinuria and several years of progressive renal dysfunction. Renal biopsy showed diffuse and global Kimmelstiel-Wilson nodule like nodular mesangial sclerosis, but she had no history of diabetes mellitus, no diabetic retinopathy and normal oral glucose tolerance. Congo red staining was negative, and immunofluorescence staining showed no immunoglobulin deposition including kappa or lambda light chains. Electron microscopy showed no electron dense deposits or organized deposits. Thus, we diagnosed idiopathic nodular glomerulosclerosis (ING). ING is a recently established clinicopathologic disease entity linked to longstanding cigarette smoking and hypertension. Obesity is also listed as a contributing factor. However, none of these factors was documented in this case. This is a valuable case of ING that suggests the existence of as-yet unknown causative factors of ING other than smoking, hypertention or obesity.