PDE8B and striatal degeneration, autosomal dominant: In 2010, a heterozygous mutation of PDE8B was first described in a German family as causative of autosomal dominant striatal degeneration (ADSD), a rare genetic disorder that is characterized by slowly progressive dysarthria, brisk deep tendon reflexes, and mild parkinsonism without tremor and poor response to l‐dopa treatment.7