Stiff Person Syndrome
ICD-10 G25.8 · ICD-11 8E4A.0.2

Stiff Person Syndrome with Insidious Onset and Chronic Course: What to Do When First-Line Immunotherapy Has Not Achieved the Target Response

Clinical Scenario

This protocol applies to patients with Stiff Person Syndrome whose symptoms began insidiously and progressed over months into a stable, chronic disease course. Functional impairment is mild to moderate, though exacerbations may occur alongside the generally chronic trajectory.

Prior Treatment — Why Escalation Is Needed

Switching between agents within the first-line immunotherapy group — specifically among IVIG, plasma exchange, and intravenous methylprednisolone — did not achieve the required treatment targets: meaningful reduction of stiffness and spasms, improved performance on timed activities, and a decrease in GlyR- and DPPX-antibody titres. This failure to reach those goals is the criterion that prompts escalation to the current protocol.

Next Step — Treatment Escalation

When switching within first-line immunotherapy does not meet treatment targets, escalation involving rituximab — a monoclonal CD20-antibody — is considered. The complete regimen, dosing approach, and decision algorithm are available in the structured protocol.

Treatment Goals
Instant Access to Structured Evidence-Based Regimens

References

DOI: 10.1002/mdc3.12629

Most frequently, there is an insidious onset with a progression over months and a subsequent stable, chronic disease course, but there may be exacerbations.

Treatment escalation e.g. with rituximab

The monoclonal CD20-antibody rituximab has also been used in SPSD.

Such an assessment may for example involve the degree and distribution of stiffness, the response to a repeated standard stimulus such as a loud clap or a cold spray to the foot sole, and appropriate timed activities like walking a predefined distance, taking a flight of stairs or, in a patient with a stiff arm, the nine-hole-peg test.

Neuronal surface antibodies can provide additional, supportive information, as for example GlyR- and DPPX-antibody titres tend to correlate with disease severity, and their decrease may herald the immunotherapy being effective.

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