Anti-Glutamic Acid Decarboxylase (GAD) antibodies are associated with not only Type 1 Diabetes Mellitus (T1DM) but also the much rarer Stiff-Person Syndrome.(1,2,3) We present a case of a young man with strongly-positive anti-GAD antibody positive T1DM, who later also developed Stiff-Person Syndrome.
This patient was diagnosed with T1DM (anti-GAD Ab 527 U/mL (<10), anti-IA2 Ab 32 U/mL (<10), anti-ZnT8 Ab <15 U/mL (<15)) at 11 years old. At 14 years old, he developed back pain and back muscle spasm which could be induced by touch and woke him from sleep. He had an abnormal posture and gait with a rounded back and “crab-like gait” maintaining external rotation of the right hip and leg, with toes pointing outward by 40˚, persistent right hip flexion and eversion of the left foot, with loss of lumbar lordosis. He also had visual disturbance. He had normal nerve conduction studies with a normal MRI brain but evidence of intravertebral disc protrusion on MRI spine, with L4/L5 moderate to severe spinal canal stenosis. Following neurological review he was given a preliminary diagnosis of Atypical Stiff-Person Syndrome, and underwent CSF studies. His initial lumbar puncture was traumatic but was positive for raised CSF anti-GAD antibody levels. He is due to undergo spinal stenosis surgery and a repeat lumbar puncture.
This is a rare but important differential diagnosis to consider for back pain and abnormal gait in GAD-positive T1DM. We discuss the diagnosis of Stiff-Person Syndrome and review available treatment modalities including benzodiazepines, baclofen, botulinum toxin, IVIG, rituximab, and haematopoietic stem-cell transplant.