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Retinitis pigmentosa (RP)

Clinical features: Retinitis pigmentosa (RP) is the name given to a group of hereditary retinal diseases characterised by a history of visual problems at dusk or in poor light (night blindness), a gradual reduction in the field of vision and a reduced or absent electroretinogram (ERG). Symptoms usually develop between 10 and 30 years of age, although in some, the diagnosis is made much earlier in childhood and in others much later in life. Most commonly a person with retinitis pigmentosa has no other problems, the condition is said to be "non-syndromic". However it can occur as part of a large number of syndromes involving other organ systems. Individuals may experience associated deafness or renal problems. In the absence of a family history, empiric recurrence risk and offspring risk figures are available.

Incidence: 1 in 3,500 to 1 in 4,000.

Inheritance: Autosomal dominant (15 ? 25%), autosomal recessive (5 ? 20%), X-linked recessive (5 ? 15%), unknown; isolated case in family (40 ? 50%).

Gene: Non-syndromic RP shows genetic heterogeneity (many different genes cause the same condition). At the time of writing (January 2006) 40 genes have been isolated, 13 are associated with autosomal dominant RP, 22 autosomal recessive RP and 5 X-linked RP. For the majority of RP genes many different mutations have been identified, although a few specific mutations are relatively common. DNA testing is possible for some families, particularly those which show a clear X-linked recessive pattern of inheritance.

Carrier testing: Carrier females of X-linked recessive RP may be identified using ophthalmic examination, electroretinograms and DNA linkage studies or occasionally by direct mutation detection.

Patient support groups

British Retinitis Pigmentosa Society
PO Box 350
Buckingham
MK18 1GZ
Tel:  0845 123 2354 (helpline)
Tel:  01280 821334 (office)
Fax: 01280 815900
Web: www.brps.org.uk