Mutations of the parkin gene on chromosome 6 cause autosomal recessive, early 
onset parkinsonism. This is the most frequent form of monogenic parkinsonism so 
far identified. The associated phenotypical spectrum encompasses early onset, 
levodopa-responsive parkinsonism (average onset in the early 30s in Europe), and 
it overlaps with dopa-responsive dystonia in cases with the earliest onset, and 
with clinically typical Parkinson's disease in cases with later onset. Despite 
clinical features, Lewy bodies are not found at autopsy in brains of patients 
with parkin mutations. The parkin protein possesses ubiquitin ligase activity, 
which is abolished by the pathogenic mutations.