Identification of the first in cis mutations in MYH9 disorder.

Here, we report the first in cis mutations in exon 1 of the MYH9 gene in a patient with MYH9 disorder. The patient was a 5-yr-old girl with macrothrombocytopenia and conspicuous cytoplasmic inclusion bodies in neutrophils. Immunofluorescence analysis of neutrophil non-muscle myosin heavy chain-II A (NMMHC-IIA) indicated several cytoplasmic spots of NMMHC-IIA aggregates that were circular to oval in shape (type II pattern). Mutational analysis showed two mutations, c.99G > T and c.103C > G, which would result in p.W33C and p.P35A, respectively, in exon 1 of the MYH9 gene. In addition, concurrent mutations were present on the same chromosome. Inclusion bodies are usually faint or mostly invisible in MYH9 disorders with a mutation in exon 1. In this case, double mutations might have caused the large myosin protein aggregation and accumulation. Although not observed in this patient, the development of Alport manifestations should be monitored by careful follow-up.