Severe complications in a child with achondroplasia and two FGFR3 mutations on the same allele
ABSTRACT We describe a unique case of achondroplasia with associated complications, including severe respiratory problems. Molecular analysis of the fibroblast growth factor receptor type 3 (FGFR3) gene in this patient showed the common p.G380R mutation and a second novel p.L377R mutation. An allele-specific PCR demonstrated that these mutations were on the same allele (cis). Both mutations were not present in the parents and appear to have occurred de novo. To our knowledge, this is the first report in the literature on an achondroplasia patient with two FGFR3 mutations on the same allele.
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ABSTRACT: Severe achondroplasia with developmental delay and acanthosis nigricans (SADDAN) is an extremely rare severe skeletal dysplasia characterized by significant developmental delay, brain structural abnormalities, hearing loss, and acanthosis nigricans. The disorder is the result of a single missense mutation at codon 650 (p.Lys650Met) in the fibroblast growth factor receptor 3 gene (FGFR3). We describe a child who initially presented with a mild achondroplasia or hypochondroplasia like phenotype. Molecular analysis of the FGFR3 gene showed the common SADDAN mutation and a second novel mutation at codon 651 (p.Thr651Pro). Both mutations were shown to occur on the same allele (cis) and de novo. Transient transfection studies with FGFR3 double mutant constructs show that the p.Thr651Pro mutation causes a dramatic decrease in constitutive receptor kinase activity than that observed by the p.Lys650Met mutation. Our data suggest that the molecular effect by the p.Thr651Pro is to elicit a conformational change that decreases the FGFR3 tyrosine kinase activity, which is constitutively activated by the SADDAN mutation. Due to the inheritance of both a gain-of-function and a loss-of-function mutation, we conclude that a reduction of constitutive activation caused the milder skeletal phenotype. Although the occurrence of double mutations are expected to be rare, the presence of other FGFR3 modifiers may be responsible for some of the clinically discrepant skeletal dysplasia cases. © 2013 Wiley Periodicals, Inc.American Journal of Medical Genetics Part A 01/2014; 164(1):243-50. DOI:10.1002/ajmg.a.36236 · 2.05 Impact Factor
American Journal of Medical Genetics Part A 05/2014; 164(5). DOI:10.1002/ajmg.a.36449 · 2.05 Impact Factor
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ABSTRACT: An opportunity to explore osteological features of a form of disproportionate dwarfism is presented by a recent archaeological discovery. Excavation of a predominately nineteenth century Dutch cemetery from the rural, agricultural village of Middenbeemster revealed an older adult female with skeletal changes consistent with achondroplasia. The most marked features are a rhizomelic pattern of shortened and thickened upper and lower limbs, frontal bossing and a moderately depressed nasal bridge, small lumbar neural canals with short pedicles, bowing of the femora and tibiae, and short stature (130.0 ± 5 cm). However, some common features of achondroplasia like cranial base reduction and shortened fingers and toes are absent. The alternative diagnosis of a more mild form of short-limbed dwarfism, hypochondroplasia, is explored and aided by archival identification of the individual and her offspring. Five offspring, including three perinates, a 10-year-old daughter, and a 21-year-old son, are analysed for evidence of an inherited skeletal dysplasia. The unique addition of family history to the paleopathological diagnostic process supports a differential outcome of hypochondroplasia. This combination of osteological and archival data creates a unique opportunity to track the inheritance and manifestation of a rare disease in a past population.12/2013; 3(4). DOI:10.1016/j.ijpp.2013.08.004