Juvenile Paget’s disease: Report of a family with a novel missense mutation and unique radiological manifestations in a heterozygote

Abstract

Abstract Juvenile Paget’s disease (JPD) is a rare, generalized skeletal disorder characterized by markedly increased bone turnover secondary to enhanced osteoclastic activity. The patients with JPD develop progressive, widespread skeletal involvement and non-skeletal manifestations. Objectives To identify the characteristic molecular, biochemical, radiological, and audiological findings in three siblings with JPD associated with intrafamilial phenotypic variability. Patients and Methods A Saudi family with 3 affected siblings was recruited. Biochemical measurement of serum alkaline phosphatase and markers of bone turnover were performed. Genetic testing and sequencing of a panel of 22 known genes for skeletal dysplasia with increase bone density were performed by next generation sequencing (NGS). Radiological and audiological assessment were also performed. Results Patients showed marked elevation of serum alkaline phosphatase and markers of bone turnover. A novel homozygous mutation c.433T>G (p.Cys145Gly) in exon 3 of TNFRSF11B gene was identified in the 3 affected siblings. Both parents were heterozygous for the mutation. The heterozygote father had thickening of calvarium, a radiological manifestation of JPD. The eldest child (index case) had a unique striking distortion of the skull bones as evidenced by 3-D computed tomography of skull. He had also bilateral inner ear structural deformity and severe sensorineural hearing loss. Conclusions: JPD is a rare disorder that can be highly overlooked due to phenotypic overlap with other disorders of skeletal dysplasia. Mutations affecting cysteine residues result in the most severe JPD phenotypes. NGS is useful for early diagnosis of JPD, a prerequisite for successful treatment strategy.