Pulmonary function tests reveal unrecognised lung dysfunction and have independent prognostic significance in patients with systemic AL amyloidosis

Abstract

Background Lung involvement in AL amyloidosis is not very common, but post-mortem data and retrospective studies suggest it is likely underrecognized. Aim To perform a comprehensive evaluation of lung function with pulmonary function tests (PFTs) in patients with newly diagnosed AL amyloidosis. Methods A prospective, non-interventional study of 139 consecutive patients with newly diagnosed AL amyloidosis. Results PFTs indicated normal breathing physiology in 68% of patients, obstructive in 9% and restrictive in 23%; the latter was associated with worse survival (28.6 vs 76 months for obstructive/normal physiology, p = 0.002) and remained significant after adjustment for Mayo stage and abnormal chest-CT. Forced vital capacity <80% of predicted value, forced expiratory volume <80% of predicted value, and carbon monoxide diffusion capacity <70% were independently associated with poorer survival. Respiratory muscle strength (as assessed by maximal expiratory (Pe) and inspiratory (Pi) pressure) was affected in most patients (64% had Pi < 55% and 57% had Pe < 70% of predicted values). Pe% was an independent prognostic factor for survival (HR: 0.984 per 1% unit increase, p = 0.007). Conclusions Pulmonary dysfunction, as assessed with PFTs, is common and underrecognized in patients with systemic AL amyloidosis, with significant prognostic and potentially therapeutic implications, independent of the degree of cardiac dysfunction or chest-CT findings.