Progressive Retinal Atrophy MERTKA / Retinopathy (MERTKA-PRA)
MERTKA-PRA is a new and unique form of PRA characterized by the multifocal appearance of red and brown discoloration of the tapetal fundus followed over time by thinning of the retina.
Electroretinography revealed a gradual loss of both rod and cone photoreceptor-mediated function in later stages of the disease. In the few dogs that suffered from pronounced vision loss, night-blindness occurred first in later stage, followed by decreased day-vision in the stage that follows. Histologic examinations confirmed the loss of photoreceptor cells in the late stage, and this was associated with the accumulation of autofluorescent material in the adjacent retinal pigment epithelium
A mutation in the MERTK gene was identified in the Swedish Vallhund (Västgötaspets) breed which associated with MERTK-PRA. The age of onset and severity of symptoms varies, and there is a large variability in the age of diagnosis (as early as 1.1 years and as late as 12.6 years) have been reported.
