Stiff Person Syndrome and Type 1 Diabetes Mellitus: a Case of the Chicken or the Egg?

Abstract

Anti-glutamic acid decarboxylase (anti-GAD) antibodies are linked with both autoimmune diabetes and the rare neurological disorder stiff person syndrome (SPS). SPS is an uncommon autoimmune-mediated condition characterized by painful episodic spasms and progressive muscle rigidity. We present the case of a 23-year-old non-diabetic, insulin-naïve woman with known SPS who was hospitalized for SPS-related symptomatology. The patient quickly developed type 1 diabetes mellitus (T1DM) with unexpectedly large insulin requirements. To our knowledge, there are no other reports describing rapid T1DM development during an acute hospitalization for SPS and fewer than 5 case reports describing the association of SPS with extreme insulin resistance. Our case highlights the key clinical features, pathology, and pathogenesis of both SPS and T1DM and explores the relationship between the two disease processes.

Keywords: anti-glutamic acid decarboxylase (anti-GAD) antibodies; stiff person syndrome; type 1 diabetes mellitus.

Figure 1

No unified diagnostic criteria for SPS exists; however, the above clinical diagnostic criteria ^,, for SPS have been generally accepted in practice and in research characterization of the disease.

Figure 2

Comparison of stiff person syndrome (SPS) and type 1 diabetes mellitus (T1DM). GAD, glutamic acid decarboxylase; IAA, insulin autoantibodies; IA2A, insulinoma-associated antigen 2; ZnT8A, zinc transporter 8 antibodies; GlyR, glycine receptor antibodies; DPPX, dipeptidyl peptidase-like protein 6; GABAaR, γ-aminobutyric acid-A receptor antibodies. Asterisk symbol indicates anti-GAD titers are generally < 2000 U/mL in isolated T1DM; however, rare reports of titers > 2000 U/mL exist. Dagger sign indicates SPS anti-GAD titers start at ≥ 2000 U/mL ^, with reports of titers up to 144,000 U/mL.