A heterozygous variant of SON gene in child with ZTTKS

Abstract

Abstract Background Zhu-Tokita-Takenouchi-Kim syndrome (ZTTKS) is a rare, autosomal dominant genetic disorder caused by the variant of SON gene. Till now, only about 60 cases of ZTTKS were reported to date worldwide. Most pediatricians have limited knowledge about the disease, which leads to delays usually in diagnosis. Case presentation: A girl with feeding difficulties, hypotonia, and poor overall growth were noted. Physical examination showed a height of 77cm (< -10 SD) and a weight of 8kg ( < − 5 SD) at the age of 9.5 years old. She cannot communication and stand till now. She had characteristic dysmorphic facial features, including frontal bossing, small ophthalmic fissure, downslanting palpebral fissures, broad nasal bridge, nostril upturned thin upper lip, small mouth, low-set protruding ear, sparse hair, high-arched palate, edentulous, enamel dysplasia, and long and adduction left thumb. Extremely low insulin-like growth factor-1 (22.4 ng/mL) and low insulin-like growth factor binding protein 3 (0.72 g/ml) level was noted. Whole exome sequencing found a novel heterozygous variant, c.2207_2210del (p. Leu736Argfs*10), in the exon 3 of SON gene. Conclusions In patient with characteristic dysmorphic facial features, hypotonia, poor overall growth, and mental retardation, ZTTKS should be considered in the differential diagnosis. Next generation sequencing should perform early for these patients.