A rare case of co-existence of hereditary multiple exostoses and steroid-sensitive nephrotic syndrome

Introduction. Hereditary multiple exostoses (HME) is a rare autosomal dominant disorder, caused primarily by loss of function mutations in 2 genes EXT1 and EXT2 linked to the synthesis of heparan sulfate (HS). Deficiency of HS causes the formation of numerous benign cartilage-capped bone tumours. There is no causal treatment for this disease. Surgery is recommended only for symptomatic lesions and malignant transformations. Case Report. The case is presented of an 11-year-old boy with a pathogenic variant in the EXT1 gene and steroid-sensitive nephrotic syndrome (NS), diagnosed at the age of 8. There are only single reports of the co-existence of HME and NS. Conceivably, HS deficiency may explain ultra-structural changes in kidney glomeruli that result in NS, although unknown, second-hit risk factors seem to have significant contributions. Further research is necessary.