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Abstract Frontometaphyseal dysplasia 2 (FMD2) is a skeletal dysplasia with supraorbital hyperostosis combined with undermodeling of the bones, joint contractures and some extraskeletal features. It is caused by heterozygous mutations in MAP3K7 , encoding the Mitogen-Activated Protein 3-Kinase 7. MAP3K7 is activated by TGF-β and plays an important role in osteogenesis. Less than 20 patients with FMD2 and MAP3K7 mutations have been described thus far. The majority of the patients harbor a recurrent missense mutation, NM_003188.3: c.1454C > T [NP_003179.1: p.(Pro485Leu)], which leads to a more severe phenotype than mutations in other domains. Here we describe an additional patient with FMD2 caused by the recurrent c.1454C > T MAP3K7 mutation, identified as a de novo variant by whole-genome sequencing. The 17-year-old boy has the characteristic skeletal and facial features of FMD2. However, some novel features were also observed, including growth retardation and spina bifida occulta. In line with other patients harboring the same mutation he also showed keloid scars and had no intellectual disability. This report expands the clinical spectrum of FMD2 caused by the recurrent c.1454C > T [p.(Pro485Leu)] mutation in MAP3K7. [ABSTRACT FROM AUTHOR]

Osteogenesis imperfecta (OI) is a skeletal dysplasia characterized by brittle bones and extraskeletal manifestations. The disease phenotype varies greatly. Most commonly, OI arises from monoallelic mutations in one of the two genes encoding type I collagen, COL1A1 and COL1A2 and is inherited as an autosomal dominant trait. Here, we describe a consanguineous family with autosomal recessive OI caused by a novel homozygous glycine substitution in COL1A2, NM_000089.3: c.604G>A, p.(Gly202Ser), detected by whole-genome sequencing. The index patient is a 31-year-old Greek woman with severe skeletal fragility. She had mild short stature, low bone mineral density of the lumbar spine and blue sclerae. She had sustained multiple long bone and vertebral fractures since childhood and had been treated with bisphosphonates for several years. She also had an affected sister with similar clinical manifestations. Interestingly, the parents and one sister, all carriers of the COL1A2 glycine mutation, did not have manifestations of OI. In summary, we report on autosomal recessive OI caused by a homozygous glycine-to-serine substitution in COL1A2, leading to severe skeletal fragility. The mutation carriers lacked OI manifestations. This family further expands the complex genetic spectrum of OI and underscores the importance of genetic evaluation for correct genetic counselling. [ABSTRACT FROM AUTHOR]

WNT signaling is a key regulator of bone metabolism and its increased or decreased activity leads to skeletal disorders. Here we describe two patients with high bone mass (HBM) caused by novel mutations in two different WNT pathway components. The first patient is a 53-year-old male with HBM. He was diagnosed at adult age based on significantly increased bone mineral density (BMD). He has undergone several surgeries due to excessive bone in ear canals, bilateral jaw exostoses and mandibular tori. Radiographs show severe cortical thickening of cranial and long bones. Sanger sequencing identified a novel heterozygous mutation c.592A>T (p.N198Y) in LRP5 (Low-density lipoprotein receptor-related protein 5). The second patient, an adolescent female, was diagnosed with skeletal dysplasia in early childhood. She had macrocephaly (head circumference +6.0 SD), facial dysmorphism, delayed motor development, laryngomalasia and epilepsy. Radiographic findings were consistent with osteopathia striata with cranial sclerosis. A novel heterozygous frameshift mutation c.655del (p.E219Rfs*63) in AMER1 (APC Membrane Recruiting Protein 1) was identified. Although both mutations are predicted to lead to increased WNT signaling with a consequent increase in bone formation, the resulting phenotypes are different; cranial sclerosis versus macrocephaly, long bone cortical thickening versus vertical striations and discordant neurological development. This report underscores the diversity of genotypes and phenotypes of HBM and facilitates their differential diagnosis. [ABSTRACT FROM AUTHOR]