Clinical & Biological Features

PD presents with a range of clinical symptoms and biological features measurable both in living patients and in post mortem examination (Jankovic, 2008). This section of the PD Guide describes the clinical and biological presentation of PD and the various investigative tools by which these features are measured.

Diagnosis of PD in living patients always carries a degree of ambiguity, for several reasons. There is substantial overlap of PD symptoms with those of other neurodegenerative diseases. Coupled with patient-to-patient variations in symptom presentation over the course of disease progression, this overlap makes a definitive differential diagnosis based on clinical symptoms impossible. At present, there are no definitive biomarkers measurable in living patients.  A diagnosis of PD is not considered definitive until post mortem examination of brain tissue confirms the presence of pathological cellular inclusions known as Lewy bodies.

It is notable that carriers of some genetic mutations associated with PD present patterns of symptoms and pathological signs that differ from those observed in sporadic cases. There is evidence based on the presentation of specific clinical symptoms for the existence of subtypes of PD patients.