Abstract
Stiff-person syndrome (SPS) is highly associated with anti-glutamic acid decarboxylase (GAD) antibody. However, GAD antibodies alone appear to be insufficient to cause SPS, and they possibly are involved in only part of its pathophysiology. It is suspected that the symptoms of SPS get precipitated by external stimuli. Here, we briefly introduce the case of a patient with latent autoimmune diabetes who developed SPS through the action of subcutaneously injected insulin. A 43-year-old man was diagnosed with diabetes and initially well-controlled with oral hypoglycemic agents but progressed to requiring insulin within 1 year of diagnosis. Two months after the initiation of basal insulin therapy, he presented with abdominal stiffness and painful muscle spasms, involving the lower limbs, which resulted in walking difficulty, and thus, he refused insulin injections thereafter. He had been treated with oral anti-diabetic agents instead of insulin for 10 years until premixed insulin twice daily was started again due to poor diabetes control. Immediately after insulin injection, abdominal muscle rigidity and spasms were noted. When insulin was not administered, frequent episodes of diabetic ketoacidosis occurred. Serum GAD antibody test was positive and there was no positivity for islet antigen-2 antibody. A glucagon stimulation test demonstrated relative insulin deficiency, indicative of latent autoimmune diabetes in adults (LADA). Tolerable muscle rigidity was achieved when the dosage of basal insulin was split into two separate daily injections with lower amounts of units per injection. This case highlights a different form of autoimmune diabetes in SPS. To our knowledge, this is the first report of SPS described shortly after the initiation of insulin therapy that required basal insulin to achieve tolerable muscle symptoms and better glucose control, without the development of diabetic ketoacidosis.
Highlights
Stiff-person syndrome (SPS) is a rare autoimmune neurological disorder and highly associated with glutamic acid decarboxylase antibody (GAD-Ab) positivity
The blockade of glutamate decarboxylase (GAD), a critical enzyme involved in inhibitory pathways, and subsequent decline in the levels of Gamma aminobutyric acid (GABA) in the central nervous system have been suggested to be associated with a loss of neural inhibition, evidence for a causative link between GAD antibodies and SPS pathogenesis is still lacking [1]
GAD is found in non-neuronal tissues, such as pancreatic beta cells, testes, and oviducts, so SPS is associated with other endocrine disorders [6, 7]
Summary
Stiff-person syndrome (SPS) is a rare autoimmune neurological disorder and highly associated with glutamic acid decarboxylase antibody (GAD-Ab) positivity. The patient’s symptoms of jerky myoclonus-like movement, abdominal stiffness with painful spasms, and muscle rigidity were exacerbated by sound, anxiety, and subcutaneous insulin injections, regardless of the treatment regimen (Insulatard or regular insulin). He refused insulin therapy, resulting in poor glycemic control for 10 years, which resulted in glycated hemoglobin (HbA1c) values persistently >8.0% (64 mmol/mol) with only oral anti-diabetic drugs (metformin 2,000 mg/day, sitagliptin 100 mg/day, glimepiride 8 mg/day, and acarbose 200 mg/day). We splitted the administration of basal insulin into two separate injections (insulin degludec, 0.34 IU/Kg/day, injected twice daily, with a time interval between the two injections of 12 h) and oral hypoglycemic agents (linagliptin 5 mg, pioglitazone 30 mg, metformin 1,700 mg, and gliclazide MR 120 mg) were administered to prevent diabetic ketoacidosis, as the patient had subsequent tolerable abdominal stiffness
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