spastic paraplegia, autosomal recessive, type 21
spastic paraplegia, autosomal recessive, type 21A complex autosomal recessive form (OMIM:248900) of spastic paraplegia, a neurodegenerative spinal cord disease characterised by a slow, gradual, progressive weakness and spasticity of the lower limbs; initial symptoms include difficulty with balance, weakness and stiffness in legs, muscle spasms, and dragging of toes when walking. Some forms are characterised by urinary incontinence or weakness and stiffness in other parts of the body; type 21 is associated with dementia and other CNS changes, usually developing in early adulthood. It is slowly progressive: cerebellar and extrapyramidal signs characterise advanced disease.
Thin corpus callosum and white-matter defects.
Caused by defects of SPG21, which encodes a protein thought to downregulate CD4-dependent T-cell activation.