Patients with mutations in the Head domain of the MYH9gene
Patients 1-6 presented at the age of ≤1 year. They were diagnosed with alloimmune thrombocytopenia (patients 3, 5 and 6), or cITP (patients 1 and 2). Their platelet count range was 2,000-65,000/uL. Patients 1-3 had mucocutaneous bleeding. Patients 1 and 6 were treated with prednisolone while patients 3 and 5 received intravenous immunoglobulin. Patient 4 was initially suspected of MYH9 disorder because granulocyte IB were observed by a hematologist from TMSG. IFA demonstrated small diffuse precipitation in all patients except patient 6, who had small-to-medium diffuse precipitation. Five out of six patients had mutations in exon 1, of which p.S96L is the most common (Table 1 and Figure 1).
Non-HMs were identified in patients 1, 3 and patient 6. The hearing test of patient 6, at 5 years old, showed mixed hearing loss (Right ear: hearing frequency 1 kHz at 22 dB for air and 30 dB for bone, Left ear: hearing frequency 4 kHz at 40 dB). This patient had a high urine protein/creatinine ratio of 0.49 and had been treated with an angiotensin inhibitor after diagnosis.