Do not stop at the variant: a reversible cause of small-fiber neuropathy symptoms in an ATTRv carrier.

BACKGROUND: Presymptomatic genetic testing in relatives of hereditary transthyretin amyloidosis (ATTRv) index cases enables early carrier identification and timely treatment, but a confirmed pathogenic variant carries the risk of premature diagnostic closure when new symptoms arise. CASE PRESENTATION: A 25-year-old asymptomatic carrier of TTR: p.Val142Ile, whose father had neurological-predominant ATTRv, developed lower limb heaviness, burning pain, hyperesthesia, dysautonomia, and gastrointestinal symptoms. Cardiac work-up was unremarkable; electrochemical skin conductance testing was abnormal and gastric solid emptying scintigraphy was borderline. Before pursuing skin biopsy, a broad differential was investigated, revealing profoundly suppressed thyroid-stimulating hormone (TSH), elevated total triiodothyronine (T3), positive anti-thyroid peroxidase antibody (anti-TPO) and positive TSH receptor antibody (TRAb), confirming Graves' disease. Antithyroid treatment led to normalization of thyroid function and improvement of symptoms. CONCLUSION: Autoimmune thyroid disease may be an underrecognized, reversible cause of neuropathic symptoms. Systematic differential diagnosis is essential before attributing new symptoms to amyloidosis, preventing unnecessary initiation of disease-modifying therapy in patients with treatable alternative etiologies.