Spondylo-meta-epiphyseal dysplasia (SMED), short limb-hand abnormal calcification type: Further expanding the mutational spectrum and dental findings of three new patients

Genetic skeletal disorders are clinically and genetically heterogeneous group of disorders that affect the normal development, growth, and maintenance of the human skeleton. Spondylo-meta-epiphyseal dysplasia, short limb-abnormal calcification type (SMED-SL/AC; MIM# 271665) is a rare autosomal recessive genetic skeletal disorder characterized by distinctive facial features, disproportionate short stature, vertebral, metaphyseal, and epiphyseal abnormalities. This unique phenotype is caused by biallelic loss-of-function variants in Discoidin domain receptor 2 gene (DDR2, MIM# 191311). To date, only 10 pathogenic variants (six missense, two nonsense, one deletion, and one splice site) in DDR2 have been reported in patients with SMED-SL/AC. Dental anomalies related to skeletal dysplasia can include various abnormalities in the number, shape, and position of teeth in the jaw, as well as enamel hypoplasia and dentinogenesis imperfecta. Although abnormal dentition has previously been reported, orodental findings were described in only six patients with SMED-SL/AC. This study aimed to define the clinical, dental, radiological, and molecular findings of three new SMED-SL/AC patients from three unrelated families. Three DDR2 variants, two of which were novel, were detected with the aid of Sanger sequencing. Interestingly, one of the patients was diagnosed with Wilson's disease (WD) during the follow-up, a co-occurrence that has never been reported in patients with SMED-SL/AC so far.