Bone Abstracts

Background: Mucopolysaccharidosis IV is a rare, autosomal recessive disorder. Common presenting features include severe short stature, kyphoscoliosis, genu valgum, cloudy cornea, osteoporosis, mild coarsening of facial features, joint restriction in some large joints. Skeletal dysplasias should be considered in its differential diagnosis. Here we present a case whose initial diagnosis was Mucopolysaccharidosis IV and was diagnosed with osteogenesis imperfecta (OI) by COL1A2 mutation analysis.

Presenting problem: A 7-year and 9-month old girl was admitted for short stature.

Clinical management: Medical history revealed backpain and three fractures due to minor traumas. There was no parental consanguinity, no history of short stature and atraumatic fractures in the family. The height was 89.9 cm (−6.9 SDS), weight was 15 kg (−3.7 SDS). She had mildly coarse face, severe kyphoscoliosis and genu valgum. Teeth apperared translucent and sclerae were blue-grey. The hearing and intelligence were normal. She had slightly elevated ALP and mildly low 25OHD levels (298 IU/l, 16.4 ng/ml, respectively), laboratory tests were otherwise normal. X-rays revealed severe platyspondyly, bowing in the diaphysis of long bones and generalised hypomineralisation. She was diagnosed with MPS IVA in another center but in the follow-up period it was excluded with the normal enzymatic activity of N-acetylgalactosamine-6 sulfatase. In the light of her medical history and skeletal findings OI was considered. The mutation analysis revealed a heterozygous splice site mutation that substitution to A from G within intron 40 at c.2565+1 in the COL1A2 gene. Oral vitamin D3 and calcium was commenced prior to intravenous pamidronate treatment.

Discussion: The present mutation was reported to lead to OI. OI is a dominantly/recessively inherited disorder characterised with increased bone fragility due to low bone mass. The clinical features of disease is highly heterogenous. It is known that mutations in COL1A1 and COL1A2 have been identified in OI types I through IV. In a previous study the same mutation was showed in a patient with type IV OI. However the clinical findings of our case have confronted us in a quite different features. Therefore, we suggest that genotype- fenotype correlation is not clear in OI everytime.

Disclosure: The authors declared no competing interests.