Most cases of Parkinsons (PD) are not known to be related to inheritance. About 1/4 people with this disorder have a relative who has PD. People with PD who are younger have an increased risk of a genetic cause of Parkinsons. People with Parkinsons who are older than 50 have a decreased risk of having a genetic cause. There are several genes that are linked to Parkinsons, but most cases are not linked to genes that have been identified.
Testing for genetic factors for Parkinsons disease is worth considering when the symptoms occur before age 50 and there is a history of a parent or sibling affected by the condition at a young age.
A more common but similar condition is essential tremor. Sometimes this condition is mislabeled as Parkinsons. This condition is often present in multiple family members.
What a doctor sees in a Parkinsons patient is increased muscle tone, slow movements, and difficulty with balance (instability). Sometimes there is a tremor at rest.
A person with essential tremor should have normal muscle tone and speed of movement, but there may be a tremor affecting the hands, the head or the speech. The hand tremor is normally absent at rest.