This is a rare condition characterized by the thinning of the bones that can cause fractures and eye abnormalities where blindness is inevitable. The bone fractures occur frequently because of severe thinning of the bones and the decreased amount of calcium in the skeletal bones. As the result, this can cause mild shortness of stature of the affected individual. The initial sign of the condition may be evident at the birth of the infant or by early infancy with blindness occurring by the young adulthood. In addition, they can also exhibit mild intellectual disability, seizures, abnormally flexible joints and weak muscle tone. This rare condition is estimated to affect around 1 in 2 million individuals.
Causes
This syndrome develops because of mutations in the gene identified as LRP5 which is essential for the production of a protein that is involved in the chemical signaling pathway affecting the cell and tissue development. This LRP5 gene particularly assists in the regulation of bone mineral density that plays important role in the development of the retina. The genetic mutation results in the prevention of the normal production of the protein or results in the production of nonfunctional protein. As the result, the absence of this protein or its function can affect the normal chemical signaling pathway that is required for the formation of the bones and the retinal development. Hence, the symptoms associated with this condition occur. This condition is inherited in an autosomal recessive pattern meaning both the copies of the gene in each cell are defective. The parents of the affected individual each carry a single copy of the defective gene but don’t typically exhibit the symptoms of the condition.
Symptoms
Osteoporosis is usually evident in early childhood and is caused by the result of a shortage of minerals such as calcium in the bones. As the result, the bones tend to become brittle and can fracture easily. The multiple bone fractures can cause the collapse of the affected vertebrae and limb deformities. This syndrome can cause severe disability and chronic bone pain. The problem with the vision can be evident at the birth or in early infancy. The eye problem can develop because of the condition that affects the light-sensitive tissue at the back of the eye called the retina.
Diagnosis
The diagnosis is based on the identification of the features associated with the condition and with various specialized tests. The eye examination and the bone phenotype are important for the diagnosis of the condition. The genetic mutation responsible for the development of the syndrome can also help confirm the diagnosis.
Treatment
The use of biphosphates should be initiated early to help prevent the bone fractures and with the bone mineral density which can improve mobility among the affected children. In addition, the vitamin D insufficiency should also be treated. The eye abnormalities should be monitored to rule out the retinoblastoma.
References
http://www.tandfonline.com/doi/abs/10.1586/17446651.3.3.337
https://ghr.nlm.nih.gov/condition/osteoporosis-pseudoglioma-syndrome#inheritance
http://disorders.eyes.arizona.edu/disorders/osteoporosis-pseudoglioma-syndrome
http://www.wohproject.org/disorders/osteoporosis-pseudogliomasyndrome/