Makindo Medical Notes.com

Retinitis pigmentosa (RP) refers to a group of diseases that affect the retina's ability to respond to light. There is generalised retinal pigment degeneration with decreased vision. Patients have difficulty seeing at night. RP combined with progressive deafness is called Usher syndrome.

About

• RP is also the manifestation of several rare neurological diseases
• Usual form is severe and AR but AD inheritance is seen and sex-linked too

Aetiology

• Most cases are due to a defect in the gene for rhodopsin
• More common in males 3:1

Conditions associated with RP

• Usher syndrome: RP combined with progressive deafness
• Bardet-Biedl syndrome
• Mitochondrial diseases
• Abetalipoproteinaemia
• Refsum disease - elevated serum phytanic acid
• Kearns-Sayre syndrome
• Lowe syndrome

Clinical

• Progressive difficulty in managing in environments of low lighting.
• Night blindness (nyctalopia) progressing to total visual loss (can see well in day but not at night)
• May begins in childhood and as time goes on to progress to tunnel vision.
• Typically issues with vision going to and from school in winter months with low light levels
• Appearance on fundoscopy of bony spicules, attenuated vessels and disc pallor

Investigations

• The electroretinogram signal is diminished - it is normal in Leber's type of optic atrophy
• Perimetry shows tunnel vision

Management

• End result is often blindness. Needs ongoing visual support.
• Vitamin A has been used to treat with fairly poor results

References