Brain biopterin and tyrosine hydroxylase in asymptomatic dopa‐responsive dystonia

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Abstract
It is assumed that brain biopterin and dopamine loss should not be as severe in asymptomatic dopa‐responsive dystonia caused by GCH1 mutations as it is in symptomatic dopa‐responsive dystonia. However, the actual status of dopaminergic systems in asymptomatic cases is unknown. In the autopsied putamen of an asymptomatic GCH1 mutation carrier, we found that brain biopterin loss (−82%) paralleled that reported in dopa‐responsive dystonia patients (−84%). However, tyrosine hydroxylase protein and dopamine levels (−52 and −44%, respectively) were not as severely affected as in symptomatic patients (exceeding −97 and −88%, respectively). Our data suggest that the extent of striatal tyrosine hydroxylase protein loss may be critical in determining dopa‐responsive dystonia symptomatology.