Difficulties in clinical diagnosis and prediction of outcome in patients with the transthyretin Met 30 mutation: Report of two cases

Abstract

Familial amyloidotic polyneuropathy (FAP) is an autosomally inherited fatal disorder characterized by peripheral and autonomic polyneuropathy. The histories of two Swedish patients with FAP transthyretin Met 30 mutation (TTR Met 30) are presented. Patient I had no family history of FAR He suffered for more than 20 years from ill-defined non progressive neurological disturbances. His nutritional status remained unchanged. Biopsies and electromyography showed no amyloid deposits or axonal polyneuropathy, however, he was positive for TTR Met 30 gene. Patient 2 had a family history of late-onset, slowly progressive FAP and experienced a very slow progress of the disease. At the onset of symptoms, amyloid deposits were found in biopsy specimens, and axonal denervation was seen on electromyography. Twenty-five years later she could still walk without a walking cane. However, after onset of gastrointestinal disturbances, a rapid impairment of her nutritional status was observed.

We conclude that the diagnosis of FAP should be based the, finding of the TTR Met 30 mutation and amyloid deposits on tissue biopsy. Other types of amyloidosis must be excluded in sporadic cases, and repeated evaluations may be necessary to identify patients with slowly progressing disease, not suitable for transplantation at an early stage.

Key Words:

• FAMILIAL AMYLOIDOTIC POLYNEUROPATHY (FAP)
• TRANSTHYRETIN (TTR)
• INBORN ERRORS OF METABOLISM.