Phenotypic variability of syndromic craniosynostosis caused by c.833G > T in FGFR2: Clinical and genetic evaluation of eight patients from a five-generation family.

OBJECTIVE: Craniosynostosis is the result of the early fusion of cranial sutures. Syndromic craniosynostosis includes but not limited by Crouzon syndrome and Pfeiffer syndrome. Considerable phenotypic overlap exists among these syndromes and mutations in FGFR2 may cause different syndromes. This study aims to investigate the explanation of the phenotypic variability via clinical and genetic evaluation for eight patients in a large pedigree. METHODS: For each patient, comprehensive physical examination, cranial plain CT scan with three-dimensional CT reconstruction (3D-CT), and eye examinations were conducted. Whole exome sequencing was applied for genetic diagnosis of the proband. Variants were analyzed and interpreted following the ACMG/AMP guidelines. Sanger sequencing was performed to reveal genotypes of all the family members. RESULTS: A pathogenic variant in the FGFR2 gene, c.833G > T (p.C278F), was identified and proved to be co-segregate with the disease. Some symptoms of head, hearing, vision, mouth, teeth expressed differently by affected individuals. Nonetheless, all the eight patients manifested core symptoms of Crouzon syndrome without abnormality in the limbs, which could exclude diagnosis of Pfeiffer syndrome. CONCLUSION: We have established clinical and genetic diagnosis of Crouzon syndrome for eight patients in a five-generation Chinese family. Variability of clinical features among these familial patients was slighter than that in previously reported sporadic cases.

A novel variant of osteogenesis imperfecta type IV and low serum phosphorus level caused by a Val94Asp mutation in COL1A1.

Osteogenesis imperfecta (OI) is a rare congenital disorder characterized by bone fragility and fractures, and associated with bone deformity, short stature, dentin, ligament and blue­gray eye sclera. OI is caused by a heterozygous mutation in collagen α­1(I) chain (COL1A1) or collagen α­2(I) chain (COL1A2) genes that encode α chains of type I collagen. Collagen α chain peptide contains an N­propeptide, which has a role in assembly and processing of collagen. Point mutations in the N­propeptide domain appear to trigger OI. In the present study, a novel heterozygous missense mutation, c.281T>A (p.Val94Asp), was identified in the von Willebrand C domain of N­terminal of type I collagen in an individual with type IV OI. The majority of N­terminal mutations are associated with OI/Ehlers­Danlos syndrome (EDS); however, in the present study, the affected individual did not suffer from EDS and the level of serum phosphorus of the patient was low (0.67 mmol/l). A number of clinical phenotypes were observed at the same variation site or in the same region on the polypeptide chain of COL1A, which suggests that additional genetic and environmental factors may influence the severity of OI. The present study may provide insight into the phenotype­genotype association in collagen-associated diseases and improve clinical diagnosis of OI.

A rare occurrence of two large de novo duplications on 1q42-q44 and 9q21.12-q21.33.

De novo partial distal 1q trisomy is uncommon and mostly occurs in combination with monosomy of another chromosome due to a parental translocation. Distal 1q trisomy co-occurring with another de novo duplication on a separate chromosome is extremely rare. Here, we reported a patient carrying two large de novo interstitial duplications including a 20Mb duplication at 1q42-q44 and a 14.2Mb duplication at 9q21.12-q21.33. The patient presented with features of pre- and postnatal growth retardation, low birth weight, failure to thrive, developmental delay and frequent infection. Her dysmorphic features included macrocephaly, prominent forehead, triangular face, wide fontanelle, hypertelorism, flat nasal bridge, tented mouth, micrognathia, protruding and low-set ears, slender limbs with toe-walking appearance. In addition, she presented with subdural hematoma. The clinical presentations of this patient are mostly consistent with those of distal 1q trisomy syndrome or 9q interstitial duplication. The interstitial 1q trisomy may have contributed to the macrocephaly, prominent forehead and limb abnormalities of our patient. Either or both de novo duplications could have contributed to the features of growth retardation, developmental delay and dysmorphic features including hypertelorism, low-set ears and abnormal nose/nasal bridge.