To the Editor: Lebwohl and colleagues1 performed M-mode echocardiography on 14 patients affected by pseudoxanthoma elasticum and found mitral-valve prolapse in 11 (71 per cent) (July 22 issue). We are conducting a multidisciplinary assessment of pseudoxanthoma elasticum. Preliminary results (unpublished) of cardiologic examinations in 28 unrelated patients do not confirm this high prevalence of mitral-valve prolapse. None of the 17 women or 11 men (mean age, 43.3 years; range, 13 to 71 years) hada systolic click, and only one had an apical systolic murmur. M-mode echocardiograms in 16 patients showed mitral-valve prolapse in 1. Two-dimensional echocardiograms in 26 patients.