OMIM ID:
Osteoporosis-Pseudoglioma Syndrome
Alternate Names
Defective Genes
Clinical Characteristics
Ocular Features
Retrolental masses often present at birth have been mistaken for retinoblastomas. Hyperplasias of the vitreous, corneal opacities, and secondary glaucoma have been described. Band keratopathy may account for some of the corneal clouding and opacities. Most patients are blind soon after birth although some retain some vision into the second decade.
Systemic Features
Some patients have been described as mentally retarded but others have normal intelligence. Hypotonia and hyperflexible joints have been noted. Bone fractures are common sometimes resulting in scoliosis, short stature and limb deformities. Radiography of the skeletal reveals porotic and thin bones.
Genetics
Inheritance
This disorder, sometimes called the ocular form of osteogenesis imperfecta, results from mutations in LRP5 (11q13.4). The same gene is mutant in the EVR4 type of familial exudative vitreoretinopathy (601813) which has some of the same ocular and bone features. Most descriptions of OPPG were published before the gene mutation was found and many reports do not include detailed ocular examinations. Certainly the two disorders are allelic and likely the same condition.
Mutations in LRP5 lead to EVR4 disease in both the heterozygous and homozygous configuration but most cases of OPPG have homozygous or compound heterozygous mutations.
Pedigree
Autosomal recessive
In order for autosomal recessive disorders to be expressed, offspring generally must inherit two mutations, one from each carrier parent. Carriers with only one mutation, such as the parents, do not have clinical disease. Note that carrier parents can expect that 1 in 4 children (25%) will inherit both mutations and have the disorder, 2 in 4 children (50%) will be carriers like their parents, while 1 in 4 children (25%) inherit neither mutation.
In order for autosomal recessive disorders to be expressed, offspring generally must inherit two mutations, one from each carrier parent. Carriers with only one mutation, such as the parents, do not have clinical disease. Note that carrier parents can expect that 1 in 4 children (25%) will inherit both mutations and have the disorder, 2 in 4 children (50%) will be carriers like their parents, while 1 in 4 children (25%) inherit neither mutation.