PIRA
Also written as: PIRA — Progression Independent of Relapse Activity
Progression independent of relapse activity in multiple sclerosis, representing disability accumulation without clinical relapses.
Full Definition
Progression independent of relapse activity (PIRA) describes the accumulation of neurological disability in multiple sclerosis patients that occurs without identifiable clinical relapses or new MRI lesions. This concept challenges the traditional classification of MS into relapsing and progressive forms, as PIRA can occur even in patients with relapsing-remitting disease. PIRA represents ongoing tissue damage and neurodegeneration that may be driven by compartmentalized inflammation within the CNS. Recognition of PIRA has important implications for treatment decisions and clinical trial design, as it may require different therapeutic approaches than relapse-associated worsening.
Usage
Usage note: Always capitalize PIRA; distinguish from relapse-associated worsening (RAW).
In Context
- "The patient demonstrated PIRA with gradual walking deterioration despite stable MRI findings." — Clinical assessment
- "PIRA occurred in 15% of RRMS patients over the 5-year follow-up period." — Longitudinal study