Contributor: Gordon K. Klintworth
Amyloid polyneuropathy type III (familial amyloid polyneuropathy type III, familial amyloid polyneuropathy Iowa type, familial amyloid polyneuropathy van Allen type, apolipoprotein A1 derived amyloidosis) is an autosomal dominant inherited type of amyloid polyneuropathy caused by a mutation in the APOA1 gene that encodes a major apoprotein of high-density lipoprotein. The mutation results in the deposition of apolipoprotein A-1 derived amyloid in various tissues (including peripheral nerves and the kidney). The mutant protein has arginine substituted for glycine in position 26 of apolipoprotein A-1. The polyneuropathy usually has an onset in the fourth decade with involvement of the peripheral nerves of all four extremities. The initial symptoms of the amyloidosis commonly involve the feet and hands. Gastrointestinal complaints are common and severe peptic ulcers may be present. Impotence and sphincter disturbances frequently occur. Trophic ulcers are rare. Cataracts sometimes develop. Amyloid nephropathy frequently causes a nephrotic syndrome. The average duration of illness is 12 years and renal failure is the usual cause of death.