Endocrine Abstracts

Introduction: Stiff person syndrome (SPS) is a rare neurological disease resulting in stiffness and spasm of muscles and, as a consequence, severely impaired ambulation. Pathophysiology of the disease is based on an increased muscle activity caused by the decreased level of the inhibitory neurotransmitter gamma-aminobutyric acid (GABA) due to an autoimmune attack against glutamic acid decarboxylase (GAD); enzyme which is also one of the main autoantigens of type 1 diabetes mellitus (DM). SPS is often associated with autoimmune disorders and it may rarely occur as a paraneoplastic syndrome. We present a singular case of SPS in a woman with late onset type 1 DM.

Case report: A 74 years old woman had been recently diagnosed with type 2 diabetes due to a mild hyperglycemia. Treatment with metformin was started but few months later she developed polyuria, polydipsia and weight loss (BMI 24.5 kg/m²). She was referred to our center and insulin therapy was initiated as well as autoimmunity study was requested. Blood test showed anti GAD level of 3701.9 U/ml (normal range: 0–3.9) with a very low C peptide (0.21 ng/ml, normal range: 0.9–4) so, she was diagnosed with type 1 DM. Two years later she presented with progressive gait disturbance and rigidity of lower limbs. Neurological examination revealed dystonia and tremors in lower extremities as well as areflexia in both Achilles tendons. Routine laboratory tests including complete blood count, chemistry profile, creatinine kinase, C-reactive protein and thyroid function were in the normal range. Brain and cervical spine MRIs were unremarkable but electromyography (EMG) observed continuous motor unit discharge and simultaneous co-contraction in lower extremities. SPS diagnostic was made based on the clinical findings, EMG results and a positive therapeutic response to diazepam. Treatment with benzodiazepines, gabapentin, intravenous immunoglobulin and mycophenolate was started with significant improvement observed in the follow-up.

Conclusions: SPS is a rare condition but it should be considered in any patient with bizarre gait disorder and autoimmune disease, especially type 1 DM, in order to prevent delay in diagnosis and long-term neurologic disability.