In conclusion, Takenouchi-Kosaki syndrome is a clinically recognizable human disease that is characterized by macrothrombocytopenia, intellectual disability, sensorineural hearing loss with structural brain abnormalities, camptodactyly, and frequent infections as well as a de novo heterozygous single amino acid substitution change in CDC42, i.e., p.Tyr64Cys. The gene discussed is CDC42; the disease is Macrothrombocytopenia.