A Fast-Moving Inherited Macular Dystrophy
Underneath the retina lies a thin membrane called Bruch's membrane, functioning much like a filter between the retina and the blood vessels that nourish it. In Sorsby fundus dystrophy, a faulty protein causes that filter to thicken abnormally, and the retina responds by growing new, fragile blood vessels in an attempt to compensate — vessels that leak and bleed with little provocation. It is this neovascular response, arriving decades earlier than it typically would in ordinary age-related disease, that makes Sorsby dystrophy one of the more aggressive conditions covered on this site.
For a Kenyan patient in their thirties or forties whose central vision has dropped sharply over a matter of weeks rather than years, that speed itself is often the first clue pointing toward Sorsby rather than a more gradually progressing dystrophy.
Unlike most inherited macular conditions, Sorsby dystrophy can cause genuinely sudden or rapid central vision loss in one eye, with the second eye typically following within several years. Distortion of straight lines and a rapidly expanding blurred patch in central vision are common presenting complaints, and a subtle difficulty adjusting to dim lighting sometimes precedes the more dramatic central symptoms by months or even longer.
The condition arises from mutations in the TIMP3 gene, disrupting a protein normally responsible for regulating tissue remodelling around Bruch's membrane. That membrane thickens as a result, and abnormal, leaky blood vessels then grow beneath the retina in response — a process known as choroidal neovascularisation. Inheritance is autosomal dominant, meaning a single faulty copy from either parent is enough to bring on the condition.
A fundus examination frequently reveals distinctive yellow-white deposits scattered along the retinal blood vessel arcades, a pattern experienced examiners tend to recognise quickly. OCT and OCT-angiography, or fluorescein angiography where needed, are used to detect and map any active neovascular membrane, since its presence changes the urgency of the situation considerably. Genetic testing for TIMP3 confirms the diagnosis, and given how quickly this particular condition can move, testing is arranged without unnecessary delay.
Because active neovascular membranes can worsen quickly, addressing that specific complication is always the immediate priority once identified, handled alongside our broader retinal evaluation. Once the eye has been stabilised, regenerative stem cell therapy is considered as part of a supportive plan for eligible patients, with a monitoring schedule set noticeably closer than for slower-moving dystrophies, given how aggressively this condition can progress.
Yes, and this rapid pace is actually one of the defining features of Sorsby fundus dystrophy, setting it apart from most other inherited macular conditions, which typically progress far more gradually. It's precisely this speed that makes prompt evaluation so important here.
It can be, since both involve abnormal new blood vessel growth beneath the retina and can look alike on a scan. The age at onset, the family history, and genetic testing for TIMP3 are what ultimately tell Sorsby dystrophy and the age-related form apart.
Finding an active neovascular membrane does raise the urgency, since these vessels can cause further rapid vision loss if left unaddressed. We prioritise stabilising that specific complication first before moving on to the broader retinal plan.
Not necessarily, but the risk is meaningful, since Sorsby dystrophy follows an autosomal dominant pattern, giving each child of an affected parent roughly a fifty percent chance of inheriting the faulty gene. Severity can still vary between family members, and genetic testing can offer a more precise picture for your own family.