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Prenatal diagnosis of autosomal dominant hereditary spastic paraplegia (SPG42) caused by SLC33A1 mutation in a Chinese kindred

Hereditary spastic paraplegias (HSPs), characterized by progressive and bilateral spasticity of legs, are a highly heterogeneous group of neurodegenerative disorders usually caused by progressive retrograde degeneration of motor axons in the corticospinal tracts (Fink, 2006; Salinas et al., 2008). The major diagnostic criteria are lower limb spasticity, pyramidal weakness, hyperreflexia and extensor plantar response (Salinas et al., 2008). Clinically, HSPs can be classified into pure HSP and complicated form depending on whether the symptoms occur in isolation (pure HSP) or they are accompanied by additional neurologic or systemic abnormalities, such as mental retardation, deafness, cerebellar ataxia, epilepsy, dysarthria and ichthyosis (complicated HSP). Genetically, HSPs are also extremely heterogeneous with autosomal dominant, autosomal recessive and X-linked HSP. To date, more than 40 HSP loci and 19 spastic paraplegia genes have been identified. Mutations in the genes spastin (SPG4 ), atlastin (SPG3 ) and REEP1 (SPG31 ) account for the majority of autosomal dominant form of HSP. Mutations in other genes each occur in <1% of HSP cases. Therefore, linkage analysis and mutation detection analysis are most effective for the differential diagnosis and prenatal diagnosis of HSP. In 2006 we were contacted by a family member of a large kindred with HSP for genetic counseling. After we got the approval of the Ethics Committee of Shandong University School of Medicine, and informed consents from all participants, we performed clinical examination of the family members, obtained blood samples and conducted linkage analysis. Among 57 subjects examined, 20 were diagnosed to be definitely affected, 3 mildly affected and 1 subject as an asymptomatic carrier. The inheritance pattern is clearly autosomal dominant. The affected patients in the pedigree displayed typical symptoms of pure HSP, including spasticity, increased