Autosomal recessive spastic paraplegia type 85

Autosomal recessive spastic paraplegia type 85 (SPG85) is an extremely rare hereditary spastic paraplegia caused by mutations in the AP4B1 gene. Hereditary spastic paraplegias are a group of neurodegenerative disorders characterized by progressive weakness and spasticity (stiffness) of the lower limbs due to degeneration of the corticospinal tract motor neurons. SPG85 belongs to the AP-4-associated hereditary spastic paraplegia complex, which also includes SPG47, SPG50, SPG51, and SPG52, all caused by mutations in genes encoding subunits of the adaptor protein complex 4 (AP-4). Patients with SPG85 typically present in infancy or early childhood with progressive spastic paraplegia affecting the lower extremities, global developmental delay, intellectual disability, and microcephaly. Additional features may include seizures, reduced muscle tone (hypotonia) that evolves into spasticity, speech difficulties, and thinning of the corpus callosum on brain imaging. The condition primarily affects the central nervous system, particularly the motor pathways and brain development. There is currently no cure or disease-modifying treatment for SPG85. Management is supportive and symptomatic, focusing on physical therapy to maintain mobility and reduce spasticity, antispasticity medications such as baclofen, management of seizures with antiepileptic drugs, and speech and occupational therapy. A multidisciplinary approach involving neurologists, rehabilitation specialists, and developmental pediatricians is recommended to optimize quality of life.

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