Abnormal sudomotor function in the hypomelanotic macules of tuberous sclerosis complex

To investigate the integrity of sympathetic innervation in the hypomelanoti c macules of tuberous sclerosis complex, we studied sudomotor function in n ine patients with tuberous sclerosis complex. Postganglionic sudomotor func tion was assessed using the Silastic imprint test in nine patients with tub erous sclerosis complex who have at least one hypomelanotic macule greater than 2 cm in diameter. Sweating was induced by iontophoresis with 0.5% pilo carpine nitrate and sweat droplets were counted under a microscope using a 1x1 cm grid. Silastic imprint testing of an analogous skin area contralater al to the hypomelanotic macule was measured as a control. Sweat volume quan titation using sweat collectors was performed in five of the subjects. The sweat volume collected from the hypomelanotic macule was reduced compared t o the control skin in four of the five subjects. Sweat droplet counts from the hypomelanotic macule were significantly reduced in only one of nine sub jects. These data suggest that, although there is no difference in the numb er of functioning sweat glands in most hypomelanotic macules, the sweat gla nds produce less sweat (ie, decreased sweat volume) than in normal skin. We hypothesize that focal abnormalities of sympathetic innervation might be r esponsible for the hypomelanotic macules of tuberous sclerosis complex.