You can say that this disease is a degenerative disorder characterized by the tremors, akynesia, rigidity and postural imbalance. This disorder is caused by the low concentration of the dopamine in the body.
Dopamine decreases in the body and as a result of which acetylcholine increases in the body that decreases the effect of the dopamine.
Normally this disease occurs in the old ages. It is the second major disease after the Alzheimer disease. It is basically the mutual disorder of the dopamine and the GABA receptors. It can be treated by the MAO-B inhibitors, COMT inhibitors and dopamine receptor agonist.