Autoimmune Stiff-Person Disorders Panel, Serum and CSF

Content Review: May 2023 Last Update:

Stiff-person spectrum disorders may be paraneoplastic or idiopathic and can present with a broad range of phenotypes. Antibodies found in these disorders are associated with an immune-mediated loss of neuronal inhibitory pathways, leading to hyperexcitability. 

Disease Overview

Stiff-person spectrum disorders encompass classical stiff-person syndrome, partial/focal stiff-person forms such as stiff-limb and stiff-trunk, pure cerebellar ataxia, and a severe encephalomyelitic form referred to as progressive encephalomyelitis with rigidity and myoclonus (PERM).  Symptoms commonly include exaggerated startle responses, falls, painful spasms, and stiffness. Classical stiff-person syndrome typically affects the lower back and lower extremities, whereas the focal forms are limited to either the limbs or the trunk.  Patients with PERM exhibit a more severe form that also includes dysautonomia, encephalopathy (often with seizures), and myoclonus (muscle jerking).  Treatment of patients with stiff-person spectrum disorders ranges from symptomatic medications to immunomodulatory therapy, and treatment responses vary.   

For more information about laboratory testing for autoimmune neurologic diseases, refer to the ARUP Consult Autoimmune Neurologic Disease - Antineural Antibody Testing topic.

Test Description

These serum and cerebrospinal fluid (CSF) autoimmune stiff-person disorders panels can be used for the evaluation of patients with stiffness, spasms, hyperekplexia, limb rigidity, myoclonus, or limb dystonia in the presence or absence of encephalopathy. Testing for the presence of antineural antibodies in both serum and CSF may improve diagnostic yield. Low glutamic acid decarboxylase 65-kd isoform (GAD65) antibody titers in serum should be followed by CSF testing to confirm the diagnosis. 

These phenotype-targeted panels test for the presence of antibodies associated with stiff-person spectrum disorders. Clinical phenotypes for specific antineural antibody-mediated syndromes often overlap, and phenotype-specific panels allow for rapid identification of associated antibodies, which has implications for treatment, prognosis, and cancer screening. 

For patients presenting with a broader phenotype concerning for immune-mediated movement disorder, consider ARUP’s Autoimmune Movement Disorder Panel in serum (3006206) or CSF (3006207).

Regardless of the panel chosen, order only one panel for serum and/or one panel for CSF; many antineural antibodies are redundant between these panels, and choosing based on the predominant phenotype will provide the most meaningful results. To compare these panels and the antibodies included, refer to ARUP Autoimmune Neurology Panel Components.

Testing for individual antibodies is also available separately.

Antibodies Tested and Methodology

Autoantibody Markers

Autoimmune Stiff-Person Disorders Panel, Serum (3006234) and CSF (3006235)
Autoantibody Markers Methodology
Individual Autoantibody Test Code
Serum CSF

Amphiphysin Ab, IgG

IB

2008893

3004510

DPPX Ab, IgG

CBA-IFA, reflex titer

3004359

3004512

GAD65 Ab

ELISA

2001771

3002788

Ab, antibody; CBA, cell-binding assay/cell-based assay; DPPX, dipeptidyl-aminopeptidase-like protein 6; ELISA, enzyme-linked immunosorbent assay; IB, immunoblot; IFA, indirect immunofluorescence assay; IgG, immunoglobulin G

Reflex Patterns

Autoimmune Stiff-Person Disorders Panel, Serum (3006234) and CSF (3006235): Reflex Patterns

Reflex patterns for Autoimmune Stiff-Person Disorders panels

Limitations

This panel does not include every antibody that has been associated with autoimmune stiff-person disorders:

  • Glycine receptor antibody testing is not included because it is not performed at ARUP Laboratories.
    • Glycine receptor antibody testing may be ordered by contacting ARUP Client Services at 800-522-2787 or clientservices@aruplab.com. Testing will be sent to a referral laboratory.
  • As testing for newly described antibodies becomes available and their clinical relevance is established, these panels will evolve to reflect these discoveries.

Test Interpretation

Results

Results must be interpreted in the clinical context of the individual patient; test results (positive or negative) should not supersede clinical judgment.

Autoimmune Stiff-Person Disorders Panel, Serum (3006234) and CSF (3006235): Results Interpretation
Result Interpretation

Positive for ≥1 autoantibodies

Autoantibody(ies) detected

Supports a clinical diagnosis of autoimmune stiff-person spectrum disorder

Consider a focused search for malignancy based on antibody-tumor associations

Low positive for GAD65 Ab in serum

Possible association with systemic autoimmunity not associated with neurologic disease (ie, autoimmune diabetes); interpret cautiously based on clinical presentation

Negative

No autoantibodies detected

A diagnosis of autoimmune stiff-person spectrum disorder is not excluded

References