A sporadic case of late-onset familial amyloid polyneuropathy with a monoclonal gammopathy

A 77-year-old Portuguese woman reported gradual worsening of burning and numbness in the feet and hands, fatigue, anorexia, weight loss, diarrhoea and decreased visual acuity. She had a medical history of atrial fibrillation and recent episodes of dizziness and blood pressure fluctuations. There was no relevant family history. The diagnostic workup documented a severe axonal sensorimotor peripheral neuropathy, a monoclonal IgG kappa protein on serum, a severe left ventricular hypertrophy on the echocardiogram and probable vitreous deposits of amyloid on ophthalmologic examination. Pain and dysautonomia with an axonal neuropathy and multisystemic involvement raised the possibility of amyloidosis. The presence of a detectable monoclonal protein, older age at disease onset and absence of family history of disease usually suggest immunoglobulin light-chain amyloidosis. However, in this case, both the genetic testing and the biopsy of the salivary glands confirmed transthyretin amyloidosis. In those patients with a monoclonal protein, particularly in sporadic and late-onset cases, the diagnosis of transthyretin amyloidosis can be challenging, mimicking immunoglobulin light-chain amyloidosis.