Functional study of autonomic neuropathy in primary (AL) amyloidosis

In order to evaluate autonomic function in primary amyloidosis (AL), five non invasive tests (Valsalva ratio, heart rate variation during deep breathing, 30/15 ratio, blood pressure response to standing and blood pressure response to sustained handgrip) were performed in 16 patients with positive fat tissue aspirates (FTA) for amyloid (11 females, 5 males, aged 48-85 years). Three of 16 were asymptomatic and without signs of organ involvement. Ten normal subjects and 10 patients with monoclonal gammopathy of undetermined significance (MGUS) of similar age were studied as controls. Abnormal autonomic function was found in 15 of the 16 patients with AL amyloidosis. A severe autonomic dysfunction was observed in only 4 cases. Isolated sympathetic damage was found in 4 cases, parasympathetic damage in 5 and combined (parasympathetic and sympathetic) damage in 5. (One patient showed parasympathetic damage but he was unable to complete the sympathetic tests). No alteration was observed in the controls. Thirty months following the autonomic function investigation, 14 patients were unchanged clinically, one was worse and 2 died because of other disease. In conclusion, our results indicate that at least in some patients with less severe damage, autonomic neuropathy does not seem to carry a poor prognosis with respect to that previously reported in the literature. Since autonomic damage was also observed in biopsy positive asymptomatic patients, we suggest that autonomic neuropathy may represent an early marker of systemic AL amyloidosis.