Familial amyloid polyneuropathy (FAP) associated with
transthyretin (TTR) mutations is the commonest type of
hereditary amyloidosis. Plasma TTR is produced almost exclusively in the liver and orthotopic
liver transplantation is the only available treatment, although the clinical outcome varies.
Serum amyloid P component (SAP) scintigraphy is a method for identifying and quantitatively monitoring
amyloid deposits in vivo, but it has not previously been used to study the outcome of visceral
amyloid deposits in FAP following
liver transplantation. Whole body scintigraphy following injection of
iodine-123 labelled SAP was performed in 17 patients with FAP associated with TTR Met30 and in five asymptomatic gene carriers. Follow-up studies were performed in ten patients, eight of whom had undergone orthotopic
liver transplantation 1-5 years beforehand. There was abnormal uptake of 123I-SAP in all FAP patients, including the kidneys in each case, the spleen in five cases and the adrenal glands in three cases. Renal
amyloid deposits were also present in three of the asymptomatic carriers. Follow-up studies 1-5 years after
liver transplantation showed that there had been substantial regression of the visceral
amyloid deposits in two patients and modest improvement in three cases. The
amyloid deposits were unchanged in two patients. In conclusion, 123I-SAP scintigraphy identified unsuspected visceral
amyloid in each patient with FAP due to TTR Met30. The universal presence of renal
amyloid probably underlies the high frequency of
renal failure that occurs in FAP following
liver transplantation. The variable capacity of patients to mobilise
amyloid deposits following
liver transplantation may contribute to their long-term clinical outcome.