Clinical features and gene mutation analysis of a male case of subcortical band heterotopia caused by mosaic mutation of DCX gene / 中华神经科杂志

Objective:To investigate the clinical phenotype and genotype of a male case of subcortical band heterotopia caused by mosaic mutation of DCX gene.Methods:The clinical data and magnetic resonance imaging (MRI) features of a male case of subcortical band heterotopia diagnosed in the Department of Neurology, Children′s Hospital Affiliated to Zhengzhou University in August 2020 were analyzed retrospectively. At the same time, the whole exon sequencing of the families was performed by next generation sequencing method, the suspicious mutation was verified by polymerase chain reaction Sanger sequencing, and their genetic mutation characteristics were analyzed.Results:The proband, one male, aged 5 years and 1 month, was hospitalized in August 2020 with the complaint of intermittent convulsions for 4 years and six months. Clinical features included that limb muscle tension was slightly high, intellectual and motor development was backward, and head circumference was 48 cm. MRI of his head showed diffuse thick subcortical band heterotopia. The detection of whole exon sequencing in his family showed that there was hemizygous mosaic mutation in DCX gene (mosaic ratio 44%), c.148A>G (p.k50E). The mosaic ratios of oral mucosa and urinalysis were 38.2% and 44.8% respectively. His parents were wild-type, The mutation found in this patient has not been reported at home and abroad.Conclusions:The mosaic variation of DCX gene can cause subcortical band heterotopia in males. The variation of DCX gene c.148A>G (p.k50E) may be the possible cause of the proband, which expands the variation spectrum of subcortical band heterotopia.

Prenatal diagnosis of monogenic skeletal disorders in 22 pedigrees / 中华内分泌代谢杂志

Objective:To evaluate the clinical value of prenatal molecular diagnostic technology in preventing hereditary diseases through analysis of prenatal diagnostic characteristics in 22 monogenic skeletal disorders pedigrees.Methods:This study retrospectively analyzed prenatal molecular diagnostic results of 22 pedigrees with monogenic skeletal disorders who were admitted to Department of Osteoporosis and Bone Diseases in our hospital from January 2014 to July 2021.Results:Among 22 pedigrees, there were 10 pedigrees with X-linked hypophosphatemic rickets due to PHEX gene mutations, in which 8 fetuses were found to carry pathogenic variants; 6 pedigrees with osteopetrosis, including 3 cases of CLCN7 gene mutation, 2 TCIRG1 gene mutation, and 1 CTSK gene mutation, were detected to have 2 affected fetuses and 1 carrier. There were 4 cases of osteogenesis imperfecta, including 2 cases of COL1A1 gene mutation, 1 case of COL1A2 gene mutation, and 1 case of SERPINF1 gene mutation, in which 1 affected fetus and 1 carrier were found; only one case of osteoarthritis with mild chondrodysplasia caused by COL2A1 gene mutation was found to harbor pathogenic variant in fetus; 1 case of hypophosphatasia due to ALPL gene mutation was not detected to carry pathogenic variant in fetus. By the time of follow-up, all 12 affected fetuses were terminated, and the remaining 10 fetuses except for one case still in pregnancy were born in good condition.Conclusion:Prenatal molecular diagnosis may confirm whether the fetus carries pathogenic variants at the first and second trimesters. For monogenic skeletal disorders that comply with Mendel′s law of separation, prenatal diagnosis can be determined by calculating the probability of recurrence of offspring. In addition, for families with de novo mutations in the offspring, it is necessary to pay attention to whether there are mosaic mutations in the parents.

A novel de novo mosaic mutation in PHEX in a Korean patient with hypophosphatemic rickets

X-linked hypophosphatemic rickets is caused by loss-of-function mutations in PHEX, which encodes a phosphate-regulating endopeptidase homolog. We report a 26-year-old man with X-linked hypophosphatemic rickets who showed decreased serum phosphate accompanied by bilateral genu valgum and short stature. He had received medical treatment with vitamin D (alfacalcidol) and phosphate from the age of 3 to 20 years. He underwent surgery due to valgus deformity at the age of 14 and 15. Targeted gene panel sequencing for Mendelian genes identified a nonsense mutation in PHEX (c.589C>T; p.Gln197Ter) and a mosaic pattern where only 38% of sequence reads showed the variant allele. This mutation was not found in his mother, who had a normal phenotype. This is a case of a sporadic nonsense mutation in PHEX and up to date, this is the first case of a mosaic mutation in PHEX in Korea.