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Editor,—The osteoporosis pseudoglioma syndrome (OPS) is a rare autosomal recessive disorder characterised by severe juvenile onset osteoporosis and congenital or juvenile onset blindness. Over 40 cases have been documented but reports in the ophthalmic literature are exceedingly rare and we believe this is the first recorded case in the United Kingdom.
A white, male infant was noted by his parents to have roving eye movements and poor vision at 5 weeks of age. The pregnancy, delivery, and neonatal period were normal. On examination at 12 weeks of age he had very poor visual responses and variable horizontal nystagmus. Fundal examination showed a disordered retina with bilateral retrolental masses (Fig 1). This was confirmed by ultrasound scan and examination under anaesthesia.
A clinical diagnosis of retinal dysplasia associated with probable Norrie disease (ND) was made. A blood sample was taken for DNA analysis of the Norrie gene. He was seen from time to time over the next year and it was clear that he was completely blind with no response to light. He was poking both eyes but no complications, in particular glaucoma, had arisen.
At 1 year of age his elder brother fell on him in the bedroom resulting in a right fractured femur (Fig 2) which was treated with 2½ weeks of traction. One week later he sustained a left fractured femur while lying in his cot. This was treated with a hip spica. The combination of two fractures as a result of trivial trauma raised the possibility of non-accidental injury but review of the x rays revealed generalised osteoporosis with coarse trabeculae and thin cortices. A DEXA bone scan showed a moderate degree of osteoporosis.
The combination of multiple fractures and blindness suggested a clinical diagnosis of the rare osteoporosis pseudoglioma syndrome (OPS) as fractures are not a feature of Norrie disease. A diagnosis was important to differentiate these two diseases, OPS being autosomal recessive and Norrie disease X linked. It was not until he was 2½ years of age that final results of molecular genetic analysis showed no abnormality of the Norrie gene.
He is now 5 years of age and has suffered a total of five fractures. For the past 2½ years he has received 3 monthly bisphosphonate infusions and DEXA bone scans show improved bone density. He is developmentally delayed and has just commenced “bum shuffling.” There is also intellectual and speech delay, short stature, but no hearing impairment. His mother is currently 5 months pregnant and has been counselled that future children have a 25% chance of being affected with OPS.
This case demonstrates the blindness and skeletal handicap that characterise OPS. Other manifestations may be present but it is the eye and skeletal components which are essential for the diagnosis. Frontaliet al have reviewed OPS and shown that the clinical manifestations are in general highly variable.1
Eye features include vitreoretinal dysplasia resulting in retrolental masses. Some eyes have been mistakenly enucleated because they were thought to contain retinoblastoma.2 Other ocular features include microphthalmia, anterior chamber anomalies, cataract and phthisis bulbi, although these are all highly variable. Congenital blindness is the rule but a few patients have preserved useful vision into their teenage years.3
The osteoporosis results in multiple fractures and bone deformities. The time of onset and severity of the osteoporosis is highly variable and the history of minimal trauma is typical. As the osteopaenic process seems to stabilise with age, prophylaxis and specialist care of fractures and deformities are essential to prevent incapacitating long term problems.3 Intravenous bisphosphonate therapy may prevent progressive skeletal deformity.4
Other minor features of OPS include short stature, intellectual impairment, cardiac anomalies, hypotonia, and ligament laxity.5
The pathogenesis of OPS is unknown. It is clearly a connective tissue disorder. Clinical, biochemical, and microscopic analyses suggest the defective gene may encode a matrix protein expressed in eye and bone.6 The OPS locus has recently been mapped to 11q12–136 but the precise molecular pathology has yet to be identified.
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