Clinical and molecular findings in osteoporosis-pseudoglioma syndrome.

Mutations in the low-density lipoprotein receptor-related protein 5 gene (LRP5) cause autosomal recessive osteoporosis-pseudoglioma syndrome (OPPG). We sequenced the coding exons of LRP5 in 37 probands suspected of having OPPG on the basis of the co-occurrence of severe congenital or childhood-onset visual impairment with bone fragility or osteoporosis recognized by young adulthood. We found two putative mutant alleles in 26 probands, only one mutant allele in 4 probands, and no mutant alleles in 7 probands. Looking for digenic inheritance, we sequenced the genes encoding the functionally related receptor LRP6, an LRP5 coreceptor FZD4, and an LRP5 ligand, NDP, in the four probands with one mutant allele, and, looking for locus heterogeneity, we sequenced FZD4 and NDP in the seven probands with no mutations, but we found no additional mutations. When we compared clinical features between probands with and without LRP5 mutations, we found no difference in the severity of skeletal disease, prevalence of cognitive impairment, or family history of consanguinity. However, four of the seven probands without detectable mutations had eye pathology that differed from pathology previously described for OPPG. Since many LRP5 mutations are missense changes, to differentiate between a disease-causing mutation and a benign variant, we measured the ability of wild-type and mutant LRP5 to transduce Wnt and Norrin signal ex vivo. Each of the seven OPPG mutations tested, had reduced signal transduction compared with wild-type mutations. These results indicate that early bilateral vitreoretinal eye pathology coupled with skeletal fragility is a strong predictor of LRP5 mutation and that mutations in LRP5 cause OPPG by impairing Wnt and Norrin signal transduction.

Intravenous bisphosphonate therapy in children with osteogenesis imperfecta.

OBJECTIVE: Several studies have reported beneficial effects of bisphosphonates in children with osteogenesis imperfecta (OI); however, these studies have differed in the protocols they used, and none has been independently replicated. We intended to confirm the efficacy of a specific intravenous bisphosphonate protocol in children with moderate to severe OI. METHODS: We used the protocol described by Glorieux et al and performed a prospective clinical trial in 6 children who were aged 22 months to 14 years. Each patient received intravenous pamidronate therapy for a minimum of 2 years in cycles of 1 mg/kg daily over 3 consecutive days at a mean cycle interval of 3.8 months. Outcome measures included lumbar spine areal bone mineral density (BMD) and z score, fracture rate, and occupational therapy functional assessment with serial Pediatric Evaluation of Disability Inventory. RESULTS: While on therapy, the average annual increase in areal BMD was 48% and the average annual increase in BMD z score was 1.0. This increase in z score is statistically significant. There was no clear correlation between changes in BMD and fracture rate. All patients experienced functional improvement in mobility. CONCLUSIONS: Our results support the findings of Glorieux et al that cyclic administration of intravenous pamidronate in children with OI has beneficial effects with respect to BMD z scores and physical disability. Long-term follow-up will be required to determine whether bisphosphonate therapy will decrease fracture rates and increase mobility in children with moderate to severe OI.

Mixed clefting type in Rapp-Hodgkin syndrome.

Mixed clefting type (MCT) is the rare occurrence of cleft lip, with or without cleft palate, and cleft palate alone in the same pedigree. Here we present a family with Rapp-Hodgkin syndrome (RHS) that manifests MCT, and use this rare finding to suggest that RHS may be related not only to phenotypically similar syndromes, but seemingly dissimilar ones as well. RHS has obvious phenotypic overlap with other ectodermal dysplasia-clefting syndromes (EDCS), such as ectrodactyly-ectodermal dysplasia-clefting syndrome (EEC) and ankyloblepharon-ectodermal dysplasia-clefting syndrome (AEC), all of which show MCT. MCT is also found in the allelic disorders van der Woude syndrome (VDW) and popliteal-pterygium syndrome (PPS). Therefore, while VDW and PPS have little clinical overlap with the EDCS, the common finding of MCT may indicate closer relationships at the developmental or genetic level.