Hereditary spastic paraplegia in Western Norway

In Western Norway, two types of hereditary spastic paraplegia (HSP) were found: one type segregating as an autosomal dominant, and the other type behaving as an autosomal recessive trait. Within the last category, an infantile type might be defined, with more marked CNS affection than usual (dementia, epilepsy, cerebellar signs). In two of five families with autosomal recessive HSP, retinitis pigmentosa was found in the affected persons. Muscular atrophy was frequently found in both types of HSP, but was more pronounced in the recessive form. Cerebellar signs and cerebral/mental dysfunction also occurred relatively frequently in recessive cases. In three kindreds where HSP segregated as a dominant trait, 38 family members were examined. Of these, 23 were affected, four had unspecific neuropathy (Un), and 11 were unaffected. In five families where HSP behaved as a recessive trait, 61 family members were examined. Eleven were affected, 19 had Un, and 31 were unaffected. In the diagnosis of Un, a score system was used recording all types of neurological sign. The scores were corrected for age and sex differences based on findings in a normal population. Estimated prevalence in the area studied was 12/100,000 for autosomal dominant HSP and 2/100,000 for autosomal recessive HSP. There was a high consanguinity rate in the recessive families, so the prevalence here does not reflect the general gene frequency, which was estimated to be 1 · 2.10‐ 4 (9.7.10‐ 5 in dominant HSP). The distribution of Un in HSP families suggested different etiologies. Ratios in the recessive HSP families indicated Un to be a heterozygous manifestation. The prevalence in dominant families fitted the hypothesis that Un occurs here as a polygenic trait. Clinical differences in Un also supported these conclusions.