Review Question - QID 210229

Type V OI is characterized by autosomal dominant inheritance, no Type I collagen mutation, hypertrophic callus, and congenital radial head dislocations.

Type V OI is a rare form of OI caused by a gene mutation encoding interferon-induced transmembrane protein 5 (IFITM5). There are no defects or deficits in Type I collagen, but, microscopically bone appears abnormal and these patients share a similar phenotype to other OI patients (the same is true for OI Types VI and VII). Anterolateral radial head dislocations are associated with Type V OI, as well as hyperplastic callus formation in response to fractures and ossification of the interosseous membranes of the forearms and legs. Bisphosphonate treatment appears to be beneficial in this group, reducing fracture rates and improving mobility.

Roberts et al. wrote a review article discussing orthopaedic considerations for the adult with OI, affecting about 50,000 people in the United States. In the adult population, osteoarthritis, scoliosis, spondylolisthesis, brittle dentition, hearing loss, cardiac valve abnormalities, and basilar invagination may be present. The authors suggest non-operative management for acute fractures in adults with OI due to complications associated with both surgical and non-surgical management, as well as suggest load-sharing intramedullary devices and the avoidance of locking plates and excessively rigid fixation when surgery is indicated.

Trejo et al. provide a review article discussing updates in the diagnosis and treatment of OI in adults and children. They discuss the most common mutations in OI, COL1A1 or COL1A2 (genes which code for type I alpha chains), but also note the 17+ gene mutations more recently associated with OI. They further describe the role of bisphosphonates in reducing long-bone fractures in this population.

Figure A is a lateral radiograph showing a congenital radial head dislocation present in a patient with Type V OA.

Incorrect Answers:
Answer 1: Type I OI is characterized by autosomal dominant inheritance, a quantitative disorder in collagen, blue sclerae, hearing deficits, and presentation at preschool age; it is the mildest survivable form of OI.
Answer 2: Type II OI is characterized by autosomal recessive inheritance, a qualitative defect in collagen, blue sclerae, and is lethal in the perinatal period.
Answer 3: Type III OI is characterized by autosomal recessive inheritance, a qualitative defect in collagen, normal sclerae, and fractures at birth; it is the most severe survivable form of OI.
Answer 4: Type IV OI is characterized by autosomal dominant inheritance, a qualitative defect in collagen, and normal sclerae; it is the most moderate form of OI.