Abstract
Transthyretin familial amyloid polyneuropathy (TTR-FAP) is a life-threatening autosomal
dominant disease caused by the deposition of amyloid fibrils composed of TTR proteins.
Symptoms of this disease include progressive sensorimotor neuropathy, cardiomyopathy,
and involvement of other organs. We described a pediatric case of extremely early
onset TTR-FAP with a TTR Leu55Pro mutation. A 17-year-old boy began to suffer from lower limb weakness, gait
disturbance, and decreased sensation from 14 years of age onward. He presented with
hypertrophic cardiomyopathy, periorbital and scleral ecchymosis, anhidrosis, orthostatic
intolerance, and gastrointestinal autonomic dysfunction including nausea, vomiting,
and diarrhea alternating with constipation. The patient's older sister had developed
similar gastrointestinal symptoms from 20 years of age onward and was diagnosed as
having hypertrophic cardiomyopathy. The boy's biopsy results showed infiltrated amyloid
deposition on subcutaneous fat tissue and endocardium. Genetic analysis of the TTR gene demonstrated that both the patient and his sister had a pathogenic mutation,
c.224T > C (Leu55Pro). Both patients were prescribed tafamidis, a TTR stabilizing
agent. Although a majority of TTR-FAPs occur during adulthood, it should be suspected,
even in pediatric populations, when symmetric length dependent neuropathy occurs in
conjunction with a family history of neuropathy, autonomic neuropathy, and/or cardiomyopathy.
Keywords
amyloid neuropathy - transthyretin - Leu55Pro - early onset
