Supplementary Material for: Unusual cause of thrombocytopenia and renal failure in a 14-year-old boy (MYH9-associated disorders)

MYH9-associated disorders represent rare group of autosomal dominant diseases and are caused by pathogenic mutations in the MYH9 gene. Clinically are represented by macro-platelet-thrombocytopenia, various degrees of renal dysfunction, hearing loss and early-onset cataracts. We describe the case of 14-year-old boy in medical follow-up from birth for thrombocytopenia. Systolic hypertension and nephrotic proteinuria were detected at preventive health check. Renal biopsy revealed sing of segmental glomerulosclerosis. Dialysis treatment was needed. Before transplantation due to the finding of chronic tonsillitis with positive bacterial capture in the culture examination, tonsillectomy was indicated. Postoperative period was complicated with arterial post-tonsillectomy haemorrhage. Six months after tonsillectomy the patient underwent primary deceased-donor kidney transplantation without complication. Blood platelets showed fluctuating character in the zone of sever thrombocytopenia. However, no signs of bleeding were present. Three months after successful transplantation gene sequencing of whole exon was performed. The presence of the variant c.2105G> A [p. (Arg702HIS)] in exon 17 of the MYH9 gene has been detected. The variant c.2105G>A may be clinically manifested by progressive proteinuria with rapid deterioration of renal function. This case is an example of the delayed diagnosis of rare disease and highlights the usefulness of genetic testing.