Immune-mediated retinopathy in a patient with stiff-man syndrome

Background: Stiff-man syndrome is a rare neurological disorder characterise d by rigidity and violent spasms of the body musculature. In the majority o f patients, presence of antibodies against glutamic acid decarboxylase (GAD ), the enzyme synthesizing gamma-aminobutyric acid (GABA), suggests an auto immune attack against GABA-ergic inhibitory neurons. We report a 32-year-ol d patient with stiff-man syndrome and anti-GAD antibodies who developed sub acute progressive loss of vision in the right eye, and in the left eye 18 m onths thereafter. Methods: Ophthalmological workup included electro-retinogram (ERG), visual evoked potentials (VEP) and fluorescein angiography. Antiretinal antibodies were investigated using an indirect immunofluorescence technique on frozen sections of macaque retina with patients serum and FITC-conjugated goat an tihuman immunoglobulin. Staining with monoclonal anti-GAD65 antibodies and with serum from three healthy normals served as controls. Results: Visual acuity of both eyes decreased to 0.16 within a span of 6 we eks. Perimetry revealed a central scotoma in the visual field of both eyes. VEP and flash ERG were progressively disturbed on the right eye. On the le ft eye, initially only pattern ERG and photopic responses were abnormal. Fo llow-up recordings revealed widespread pathology of photopic single and nic ker responses. Immunofluorescence revealed strong reactivity of the inner p lexiform layer and to a lesser extent staining of the outer plexiform layer at dilutions of 1:1000 with patients serum. The same retinal staining patt ern was obtained with monoclonal anti-GAD65 antibodies. Conclusions: These findings suggest autoimmune retinopathy, mediated by ant i-GAD65 autoantibodies as the underlying cause of visual loss.