Case Presentation: Stiff Person Syndrome (SPS) is a rare chronic autoimmune condition characterized by progressive muscle rigidity, postural instability, axial and limb stiffness, anxiety, phobias, and intermittent painful muscle spasms. The prevalence is estimated at 1-2 cases per million. Affected persons are aged 20-50 years with a female predominance. Its pathophysiology involves antibodies against the GABAergic neurotransmission pathway. Six out of ten patients have antibodies against glutamic acid decarboxylase (GAD), which when present is diagnostic of the disease. However, a subgroup of patients have Stiff Limb Syndrome, in which rigidity and spasms are confined to a limb without axial involvement. Our case is that of a 44-year-old African- American female with intellectual disability and anxiety who presented with a 6-month history of worsening left lower extremity (LLE) stiffness, one month of left hip pain, and progressive ambulatory decline ultimately requiring a wheelchair for mobility. At baseline, she had basic reading and writing skills with some communication difficulties and was under the 24hr care of her parents.She had been evaluated at an outside hospital multiple times for intractable LLE pain. Despite extensive workup with lab tests, US, x-ray, CT and MRI imaging, no diagnosis was found, and she was treated for peritendinitis and anxiety with baclofen and clonazepam. However, as she progressively worsened, her family sought medical management at another facility.
Discussion: When she presented to the family medicine service at our facility, she reported episodes of anxiousness, profuse diaphoresis, and severe muscle spasms of the LLE. Her symptoms were initially deemed to be primarily psychogenic as she had decreased tenderness when distracted. On initial exam she had bilateral LE hypertonicity, hyperreflexia, LLE weakness and tenderness to palpation, left leg contracture and interestingly a positive Babinski of her right foot. Labs were notable for Creatine kinase of 547 and ESR of 94. Based on these findings along with her neurologic signs and symptoms SPS was suspected and rheumatology and neurology consults were requested. Baclofen and Clonazepam were continued, and pain was managed with opiates. Cervical and Thoracic MRI were non-diagnostic therefore serology testing for Anti-GAD antibodies was ordered. The results were positive for high anti-GAD antibodies titers and she was readmitted to the hospital for a 5-day course of IVIG therapy, during which her Clonazepam dose was increased. After positive response to treatment she was scheduled for subsequent IVIG treatments.
Conclusions: This case illustrates the complexities of diagnosing and treating uncommon neurological autoimmune conditions. Making the stiff limb syndrome diagnosis was challenging due to several confounding factors including her anxiety and intellectually disability. The tendency for medical personnel to attribute her symptoms to psychogenic factors also constituted an additional obstacle when in reality she was battling an autoimmune disease. While the patient’s anxiety was correctly identified as a factor contributing to her muscle spasms, the diagnosis failed to account for the independent relationship between stiff limb syndrome and her other symptoms. Careful consideration should be given to the potential presence of this debilitating disease especially in female patients.