Abstract #1394329: An Association Between Stiff Person Syndrome and Type 1 Diabetes

Abstract

Stiff-person syndrome (SPS) is a rare neuromuscular disorder characterized by progressive muscular spasms and rigidity. Anti-glutamic acid decarboxylase (anti-GAD) antibodies are found in type 1 diabetes mellitus (T1DM). Thirty percent of patients diagnosed with SPS have T1DM. This relationship infers that SPS and T1DM share pathogenetic features. We describe a case of a 66-year-old female with a history of SPS who developed T1DM soon after the diagnosis was made. A 66-year-old female with a history of SPS, T1DM, and discoid lupus was referred to our university endocrinology clinic for diabetes management. She had ataxia, loss of balance, and muscle stiffness since 2012. The patient was diagnosed with spinal cerebellar ataxia. She was not treated with any specific agents and continued to have left-sided muscle stiffness with preserved strength. She denied weakness, pain, paresthesia, or muscle atrophy but had difficulty ambulating due to rigidity. The diagnosis of SPS was made based on positive anti-GAD antibodies (normal < 0.02) and positive N-channel antibodies in April 2016. She required hospital admission one month later and received solumedrol and IVIG. Her HbA1c was 6.5% (normal < 5.7% of total Hgb), and glucose levels were between 200-300 mg/dL, which were treated with basal and bolus insulin. She was discharged home in May 2016 with no diabetic medications. The patient developed polyuria and polydipsia with 11 Ibs unintentional weight loss 20 days after hospital discharge. She was referred to the endocrine clinic in June 2016 for further workup. Her HbA1c was 11% with C-peptide less than 0.01 (normal 0.78-5.20 ng/mL). Basal and bolus insulin were initiated, and she remains on an insulin regimen. SPS affects an estimated one person per million per year. Decreased level of gamma amino butyric acid (GABA) in the central nervous system (CNS) in SPS has been implicated, which causes a loss of neural inhibition. Glutamic acid decarboxylase (GAD) is the main enzyme required for the GABA inhibitory pathway. Anti-GAD antibodies decrease inhibitory function within the CNS and cause increased muscle activities and subsequent muscle spasms. While most patients with T1DM do not develop SPS, most with anti-GAD-positive SPS will have or develop T1DM. Either SPS or T1DM may be diagnosed first. Awareness of these associations is essential for early diagnosis and treatment of these disorders.