Recurrent Tachycardia, Abdominal, and Chest Pain as a Presentation of Stiff Person Syndrome

<b>Introduction:</b> Stiff person syndrome (SPS) is a rare neurological disorder marked by muscle stiffness, spasms, specific electromyographic findings, and elevated levels of glutamate acid decarboxylase. Patients' symptoms and signs can be challenging for general practitioners and specialists. <b>Case report:</b> We present a case of a 56-year-old man with a history of type 1 diabetes with episodes of severe chest, abdominal, and low back pain; severe tachycardia; and difficulty with walking who was seen by different physicians over a period of 10 months without any significant improvement. He had significant weight loss during this period due to abdominal pain. Multiple studies, including computerized tomography and magnetic resonance imaging of the abdomen and entire spine, upper and lower gastrointestinal (GI) endoscopies, and cardiac catheterization, were unremarkable. The patient presented at our facility with severe abdominal and chest pain, diffuse abdominal muscle rigidity, and periods of severe tachycardia. He also had elevated creatine kinase and lactate levels. Extensive workup for infectious, cardiac, and GI processes was negative. The patient was diagnosed with SPS based on history, clinical examination, and an exceedingly high titer of glutamic acid decarboxylase. He responded well to oral diazepam, baclofen, and gabapentin, and he received a 5-day course of intravenous immunoglobulin therapy. <b>Conclusion:</b> In patients presenting with recurrent tachycardia, abdominal pain, and chest pain, SPS should be considered in the differential diagnosis. It is essential for non-neurologists to be familiar with this disorder.