Background Osteogenesis imperfecta (OI) type V is an autosomal dominant bone fragility disorder that we had described a decade ago. Recent research has shown that OI type V is caused by a recurrent c.-14C>T mutation in IFITM5. In the present study, we assessed all patients diagnosed with OI type V at our institutions for the presence of the IFITM5 mutation.

Methods IFITM5 exon 1 was analysed by Sanger sequencing in genomic DNA from 42 patients with OI type V (age: 2–67 years; 18 female).

Results The c.−14C>T mutation of IFITM5 was detected in all individuals. Indicators of disease severity varied widely: Height z-scores (n=38) ranged from −8.7 to −0.1, median −3.5. Median final height was 147 cm in men (N=15) and 145 cm in women (N=10). Lumbar spine areal bone mineral density z-scores in the absence of bisphosphonate treatment (n=29) were between −7.7 and −0.7, median −5.3. Scoliosis was present in 57%, vertebral compression fractures in 90% of patients.

Conclusions Even though the disease-causing mutation is identical among patients with OI type V, the interindividual phenotypic variability is considerable.