Phenotypic Spectrum and Clinical Approach to Early-Onset Hereditary Spastic Paraplegia.

BACKGROUND: Early-onset hereditary spastic paraplegias (HSPs) are an underrecognized cause of progressive spasticity, gait impairment, and movement disorders in children and young adults. HSPs frequently mimic cerebral palsy or genetic, metabolic, and acquired disorders, resulting in diagnostic delay. Their broad phenotypic spectrum, encompassing dystonia, parkinsonism, and neurodevelopmental features, makes them highly relevant to movement disorder practitioners across the lifespan. OBJECTIVES: This review summarizes the phenotypic spectrum of early-onset HSP, outlines a practical diagnostic approach for clinicians, and discusses therapeutic strategies. METHODS: We conducted a narrative review of PubMed-indexed literature through February 2026, supplemented by expert consensus. HSPs typically presenting in childhood and adolescence, inclusive of forms presenting across a broader age spectrum, with attention to subtypes presenting with movement disorders, were considered. RESULTS: Early-onset HSPs encompass both pure and complex forms, with SPG4 (SPAST) and SPG11 (SPG11/KIAA1840) among the most prevalent etiologies. Diagnostic challenges include distinction from cerebral palsy and other movement disorders including dopa-responsive dystonia, and identification of neuroimaging signatures in specific subtypes. A multidisciplinary management approach remains central, with spasticity, movement disorder, and neurological comorbidities each requiring targeted consideration. Disease-modifying therapies are emerging, including gene replacement strategies and antisense oligonucleotide approaches for select subtypes. CONCLUSIONS: Early-onset HSPs represent a clinically and genetically heterogeneous group with substantial overlap with movement disorder practice. Awareness of characteristic phenotypes, early genetic testing, and an individualized multidisciplinary approach are essential. Recent advances in natural history characterization and mechanism-targeted therapeutics signal a transition toward disease-modifying treatment strategies and offer cautious optimism for affected individuals.