IT HAS BEEN suggested that there may be at least three major types of amyotrophic lateral sclerosis (ALS)1,2: (1) the sporadic or classic type, (2) the familial and presumably hereditary type which accounts for about 5% to 10% of recent series of ALS cases,3 and (3) the Marianas Islands type which is so prevalent on Guam and other islands in the western Pacific.4 The relationships of these various forms of ALS to one another are still unclarified. Individual cases of the three types cannot be distinguished on clinical grounds alone. However, in the Marianas Islands type upper motor neuron features may be more prominent initially, the mean age of onset is a few years less than that of the classic type, and, pathologically, in addition to the usual findings in ALS, there are characteristic and often widespread neurofibrillary changes, even in relatively young patients.4
Hirano A, Kurland LT, Sayre GP. Familial Amyotrophic Lateral SclerosisA Subgroup Characterized by Posterior and Spinocerebellar Tract Involvement and Hyaline Inclusions in the Anterior Horn Cells. Arch Neurol. 1967;16(3):232–243. doi:10.1001/archneur.1967.00470210008002
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