A case of stiff dog syndrome associated with anti-glutamic acid decarboxylase antibodies

Abstract

Background: The stiff person syndrome (SPS) is a rare and debilitating autoimmune disorder with an unknown pathogenesis and variable clinical presentation that can present a diagnostic challenge. Although entities that clinically mimic stiff-person spectrum disorders (SPSD) have manifested in horses, they have not been reported in dogs.

Case presentation: We describe a 2-year-old beagle dog presented for progressive attacks of muscular rigidity and lordosis with superimposed spasms of the appendicular muscles triggered by tactile stimulation which resulted in marked gait impairment. Resting electromyography revealed continuous motor unit activity in the axial musculature. Compared to age-matched healthy beagle dogs, this patient had elevated glutamic acid decarboxylase antibody concentrations in serum and cerebrospinal fluid.

Conclusion: This dog presented with phenotypic, electrodiagnostic, and immunologic criterion consistent with an SPSD, including elevated anti-GAD antibody titers, which we have termed the "stiff dog syndrome (SDS)". Durable clinical improvement was achieved with symptomatic and immunosuppressive treatments including baclofen, gabapentin, prednisone, and intravenous immunoglobulin.

Keywords: Autoimmune; Canine; GAD antibodies; Stiff person syndrome.

Fig. 1

a Sagittal T2-weighted MR image revealing caudal occipital malformation, kinking of the caudal medulla, foramen magnum herniation (arrow), and a T2-hyperintense intramedullary signal within the spinal cord extending from C1 to C3. Transverse FLAIR image at the level of C2 (broken arrow, inset), demonstrating the hypointense syrinomyelic cavity in the dorsal spinal cord. b Lordotic posture resulting from axial muscular rigidity. Superimposed muscle spasms cause partial flexion of the limb joints, including the digits (arrow). c Resting EMG revealing continuous motor unit activity in the lumbar epaxial musculature