Parkinson's disease is "a progressive neurological disorder that results from the degeneration of dopaminergic nerve cells in a region of the brain that involves the control of smooth coordinated muscle movement. The first symptom of the disease is usually tremor of a limb, especially when the body is at rest." 
"The disease was first brought to the attention of the medical world in 1817 by an English physician by the name of James Parkinson, who described the condition as the “shaking palsy” because of the trembling limbs of those who suffer from the malady. Rigid or “frozen” muscles, slowness of movement and clumsiness are among other common symptoms of Parkinson’s disease." Diagnosis is often problematic "because the symptoms of the disease are often confused with those of other conditions. Misdiagnosis, especially in the early stages of the disease, is fairly common and in fact many Parkinson’s patients are never diagnosed at all (the condition may only be revealed after death during a post mortem)." "In recent years, the disease can be effectively managed as long as it’s identified early enough and appropriate treatment is started."