Bone Abstracts

Type V OI is characterised by interosseous membrane calcification and hyperplastic callus formation, but the infantile phenotype is less well recognised. In 2012 Arundel et al. described distinctive radiographic changes in an infant with type V OI. We report two further male infants (with genetic confirmation of type V OI) confirming the highly characteristic and consistent radiographic appearances that should aid early diagnosis.

Case 1 – Presented with respiratory distress at 4 weeks of age having had stridor since birth. He underwent aryepiglottoplasty aged 5 weeks. A post-operative radiograph showed a rib fracture. At 5 months, discomfort on handling led to identification of a vertebral fracture and commencement of pamidronate.

Case 2 – Presented at 6 weeks of age with multiple rib fractures. Pamidronate was started at 3–4 months of age, by which time he had sustained another rib fracture despite careful handling.

Skeletal surveys (taken at 6 and 7 weeks of life respectively) in each case revealed common radiographic appearances: flaring of metaphyses of long bones with sclerotic and irregular margins; gracile ribs; and triangular-shaped radiodensities of the anterior margins of the vertebral bodies. There was maintenance of vertebral body height initially. In both cases 25OH vitamin D concentrations were normal (57.7 and 52.4 nmol/l). Both cases were heterozygous for the c.-14C>T IFITM5 mutation confirming type V OI.

Both cases had near-identical radiographic appearances in early infancy, which are in keeping with those in the published case, as is the early development of vertebral crush fractures in case 1. In one centre, 6/7 consecutive cases of type V OI (not including either case above) had radiographic confirmation of multiple vertebral fractures by 18 months (median 13.5 m; range 7–17 m); 1/7 was initially managed overseas and the earliest confirmation of vertebral fractures was 32 months.

Early recognition of the type V OI phenotype helps remove uncertainty and target genetic testing; advice can be given to minimise the risks of hyperplastic callus; and consideration can be given to earlier intervention (bisphosphonate treatment; handling and seating advice) to minimise the vertebral deformity that commonly develops in the first year of life.

Disclosure: The authors declared no competing interests.