Serum dopamine-beta-hydroxylase in familial dysautonomia.

The mean value of serum dopamine-beta-hydroxylase (D beta H) in patients with familial dysautonomia, 1 to 5 years of age, does not differ significantly from control children of the same age (24.0 plus or minus 21.06 S.D. as compared to 34.0 plus or minus 33.12). Among patients 6 years of age and over, the mean value was slightly but significantly lower than in control subjects (62.7 plus or minus 49.61, as compared to control values of 86.1 plus or minus 54.31 p less than 0.025). However, the determination of serum D beta H does not contribute to the diagnosis of familial dysautonomia because well over half the children have levels within 1 S.D. of the mean levels of the control subjects. There is no correlation with clinical symptomatology. The disease process may tend to depress the level of serum D beta H but the effect is neither consistent nor decisive.