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A hot-spot mutation in CDC42 (p.Tyr64Cys) and novel phenotypes in the third patient with Takenouchi-Kosaki syndrome


Takenouchi-Kosaki syndrome (TKS) is a congenital malformation syndrome characterized by severe developmental delay, macrothrombocytopenia, camptodactyly, sensorineural hearing loss, and dysmorphic facial features. Recently, a heterozygous de novo mutation (p.Tyr64Cys) in the CDC42 gene, which encodes a key small GTP-binding protein of the Rho-subfamily, was identified in two unrelated patients with TKS. We herein report a third patient with TKS who had the same heterozygous CDC42 mutation. The phenotype of the patient was very similar to those of the two previously reported patients with TKS; however, she also demonstrated novel clinical manifestations, such as congenital hypothyroidism and immunological disturbance. Thus, despite the heterozygous mutation of CDC42 (p.Tyr64Cys) likely being a hot-spot mutation for TKS, its phenotype may be variable. Further studies and the accumulation of patients with CDC42 mutations are needed to clarify the phenotype in patients with TKS and the pathophysiological roles of the CDC42 mutation.

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We thank the patient and the family who participated in this study. This work was supported by a grant for the Initiative on Rare and Undiagnosed Diseases in Pediatrics (no. 15gk0110012h0101) from the Japan Agency for Medical Research and Development (AMED), Tokyo, Japan.

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Correspondence to Sumito Dateki.

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Motokawa, M., Watanabe, S., Nakatomi, A. et al. A hot-spot mutation in CDC42 (p.Tyr64Cys) and novel phenotypes in the third patient with Takenouchi-Kosaki syndrome. J Hum Genet 63, 387–390 (2018).

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