The IFITM5 mutation c.-14C > T results in an elongated transcript expressed in human bone; and causes varying phenotypic severity of osteogenesis imperfecta type V

Background

The genetic mutation resulting in osteogenesis imperfecta (OI) type V was recently characterised as a single point mutation (c.-14C > T) in the 5’ untranslated region (UTR) of IFITM5, a gene encoding a transmembrane protein with expression restricted to skeletal tissue. This mutation creates an alternative start codon and has been shown in a eukaryotic cell line to result in a longer variant of IFITM5, but its expression has not previously been demonstrated in bone from a patient with OI type V.

Methods

Sanger sequencing of the IFITM5 5’ UTR was performed in our cohort of subjects with a clinical diagnosis of OI type V. Clinical data was collated from referring clinicians. RNA was extracted from a bone sample from one patient and Sanger sequenced to determine expression of wild-type and mutant IFITM5.

Results

All nine subjects with OI type V were heterozygous for the c.-14C > T IFITM5 mutation. Clinically, there was heterogeneity in phenotype, particularly in the manifestation of bone fragility amongst subjects. Both wild-type and mutant IFITM5 mRNA transcripts were present in bone.

Conclusions

The c.-14C > T IFITM5 mutation does not result in an RNA-null allele but is expressed in bone. Individuals with identical mutations in IFITM5 have highly variable phenotypic expression, even within the same family.

Spinal fusion in children with spina bifida: influence on ambulation level and functional abilities

The aim of this study was to determine the influence of spinal fusion on ambulation and functional abilities in children with spina bifida for whom early mobilization was stimulated. Ten children (three males and seven females) with myelomeningocele were prospectively followed. Their mean age at operation was 9.3 years (standard deviation (SD): 2.4). Spinal curvature was measured according to Cobb. Pelvic obliquity and trunk decompensation were measured as well. The ambulation level was scored according to Hoffer, and functional abilities, as well as the amount of caregiver assistance, were documented using the Pediatric Evaluation of Disability Inventory. All patients were assessed before surgery and three times after surgery, with a total follow-up duration of 18 months after surgery. After spinal fusion, magnitude of primary curvature decreased significantly (p=0.002). Pelvic obliquity and trunk decompensation did not change. In spite of less immobilization as compared with other reported experiences, ambulation became difficult in three out of four patients who had been able to ambulate prior to surgery. Functional abilities and amount of caregiver assistance concerning self-care (especially regarding dressing upper and lower body, and self-catheterization) and mobility (especially regarding transfers) showed a nonsignificant trend to deterioration within the first 6 months after surgery, but recovered afterwards. From pre-surgery to 18 months after surgery, functional skills on self-care showed borderline improvement (p=0.07), whereas mobility did not (p=0.2). Mean scores on caregiver assistance improved significantly on self-care (p=0.03), and borderline on mobility (p=0.06), meaning that less caregiver assistance was needed compared with pre-surgery. The complication rate was high (80%). In conclusion, within the first 6 months after spinal fusion, more caregiver assistance is needed in self-care and mobility. It takes about 12 months to recover to pre-surgery level, while small improvement is seen afterwards. After spinal fusion, ambulation often becomes difficult, especially in exercise walkers. These findings are important for health-care professionals, in order to inform and prepare the patients and their parents properly for a planned spinal fusion.

Osteogenesis imperfecta in childhood: MR imaging of basilar impression

OBJECTIVE

To determine on radiographs the presence of Basilar Impression (BI) in children with Osteogenesis Imperfecta (OI). To confirm this sign and altered geometrical relationships of the craniocervical junction in course of time with magnetic resonance imaging (MRI).

METHODS AND PATIENTS

In a cohort study of 130 patients with OI (OI type I: 85; OI type III: 21; OI type IV: 24) lateral radiographs of the skull and cervical spine were made in a standardised way. MRI scans were performed when BI was suspected based upon protrusion of the odontoid above Chamberlain's line. Intracranial abnormalities as well as the basal angle were described. Neurological examination was performed in patients with conclusive BI at MRI-scan.

RESULTS AND DISCUSSION

In eight patients BI could be confirmed by MRI-scan. None of the children had or developed in time neurological symptoms or signs. Follow up of BI by MRI scans was done in seven patients (mean: 5 years; range: 2-6 years). No alteration of intracranial findings were seen at subsequent investigation, although in one child Chamberlain's line increased from 8 (first MRI) to 15 mm (last MRI). BI can be diagnosed by radiographs but in the extreme osteoporotic bone and altered anatomy of the craniocervical junction of children with OI MRI is preferable. As intracranial pathology can be demonstrated by MRI, also a relation can be laid to possible neurological symptoms and signs at clinical examination.

CONCLUSION

In our cohort study no alteration of the intracranial contents was seen at subsequent MRI scans. Although anatomic deformations exist in BI, no neurological symptoms or signs were present in our study and no operative reconstruction had to be performed. Periodical MRI-scan has not been of influence on the clinical decision making process. At the moment we perform a MRI-scan if BI is suspected at lateral skull radiographs. The MRI images serve as reference findings to anticipate on possible future symptoms and signs of neurological deficit.

Hemi-epiphysiodesis for unclassified congenital scoliosis: immediate results and mid-term follow-up

Complex spinal anomalies involved in congenital scoliosis consist of a jumble of vertebral defects. Progressive scoliotic curves are frequently encountered in these patients. We evaluated the results of hemi-epiphysiodesis for this patient population. A series of ten patients with unclassified scoliosis, involving multiple hemivertebrae and/or bars, was reviewed retrospectively. Hemi-epiphysiodesis was the primary treatment in all patients. Mortality, complications and wound healing problems did not occur. The average Cobb angle for all patients changed from 54 degrees (range: 40 degrees -74 degrees), preoperatively, to 58 degrees (range: 30 degrees -104 degrees), postoperatively. Applying the criterion of a minimum change of 20 degrees, to take into account measurement variability, an epiphysiodesis effect was achieved in two procedures, progression was arrested in six procedures and failure occurred in two procedures. The mean rate of Cobb angle change per annum decreased from 2.9 degrees (range: -35 degrees to 14 degrees), preoperatively, to 2.4 degrees (range: -4 degrees to 13 degrees), following surgery. Repeat surgery was necessitated by coexisting progressive kyphosis and pseudoarthrosis in one patient, and involved extension of primary epiphysiodesis in two patients. A mean intervention-free period of 58 months was established. These results suggest that hemi-epiphysiodesis stabilized the unclassified congenital scoliosis. Being under 5 years of age, having a thoracolumbar curve location, and the absence of coexisting kyphosis were found to be associated with a more favorable outcome.