| Abstract: | Menkes disease is a neurodegenerative disorder of copper metabolism. Because the enzyme dopamine-b?-hydroxylase requires copper to catalyze the conversion of dopamine to norepinephrine, we reasoned that patients with Menkes disease would have a neurochemical pattern similar to that seen in patients with congenital absence of dopamine-b?-hydroxylase, i.e., high levels of dopamine, the dopamine metabolite dihydroxyphenylacetic acid (DOPAC), and the catecholamine precursor dihydroxyphenylalanine (DOPA), and low levels of norepinephrine and its neuronal metabolite dihydroxyphenylglycol (DHPG). We measured plasma and cerebrospinal fluid (CSF) levels of catechols in 10 patients ranging in age from 9 days to 27 months. In contrast to patients with congenital absence of dopamine-b?-hydroxylase, norepinephrine levels were normal in plasma of 4 Menkes patients and in CSF of all 10 patients. However, the ratios of DOPA : DHPG and DOPAC : DHPG in plasma and CSF of Menkes patients were invariably increased beyond the ranges of control values. These neurochemical findings indicate partial deficiency of dopamine-b?-hydroxylase in Menkes patients, with compensatory increases in catecholamine biosynthesis in sympathetic nerves and in the brain. Increased tyrosine hydroxylation and increased exocytotic release of norepinephrine may be responsible for preservation of plasma and CSF norepinephrine levels in Menkes patients. The abnormal neurochemical pattern, including high ratios of DOPA : DHPG and DOPAC : DHPG, may serve as a biochemical marker for Menkes disease and provide a baseline against which the influence of proposed therapies can be judged. |
