Genetic factors in amyloidosis.

In the absence of biochemical distinctions, the nosography of the inherited amyloidoses must at present depend largely upon clinical subdivisions. In the broad classification adopted here, the disorders have for convenience been grouped according to the anatomical system that is predominantly affected. It is evident that the amyloid syndromes display considerable heterogeneity. However, they overlap. Thus in the Iowa type classified with the hereditary amyloid neuropathies (van Allen et al, 1969; Gimeno et al, 1974), renal involvement was frequent and was the usual cause of death. In the English (Zalin et al, 1974) and Scandinavian (Andersson, 1970) families with neuropathy as the predominant feature, cardiac involvement was a common finding. In certain of the conditions discussed, such as medullary carcinoma of the thyroid and Down's syndrome, amyloid deposition is merely an incidental aspect of the disorder. In those conditions in which generalized or localized amyloid deposition occupies a more central position in the clinical syndrome, an autosomal dominant inheritance has been established or suggested in the majority. An autosomal recessive inheritance has so far only been recognized in familial Mediterranean fever. In the family with hereditary amyloid heart diseases reported by Fredricksen et al (1962), the disorder was confined to a single sibship, raising the possibility of recessive inheritance. This could also be true in sporadic examples of primary amyloidosis. The dominantly inherited amyloidoses comprise a number of geographically widely scattered families with clinical pictures that do not show consistent differences between some families. The families that do not show consistent differences are not necessarily harbouring nutations at the same locus, or the same mutation at any particular locus. However, many of these dominantly inherited clinical syndromes are sufficiently different from each other and the clinical manifestations of each sufficiently consistent to indicate that separate main genes are likely to be involved...