When Hemiplegic Migraine Defies Expectations: Diagnostic Complexity in a Rare Genetic Disorder.

INTRODUCTION: Familial hemiplegic migraine (FHM) is a rare and complex inherited subtype of migraine with aura, characterised by migraine with a reversible motor aura, and may present with a wide spectrum of neurological symptoms, making diagnosis particularly challenging. CASE PRESENTATION: We report a case of FHM presenting with prolonged hemiparesis, severe headache, altered consciousness, and fever. This constellation of symptoms initially suggested acute stroke, encephalitis, or status epilepticus. A precise clinical history and targeted genetic testing (CACNA1A, ATP1A2, SCN1A, and PRRT2) proved essential for establishing the diagnosis. CONCLUSION: This case highlights the wide phenotypic variability of FHM and the risk of misdiagnosis in emergency settings. Early recognition through careful clinical assessment and appropriate genetic testing enabled appropriate management and avoided unnecessary interventions.