Tremor-Dominant in Parkinson Disease: The Relevance to Iron Metabolism and Inflammation.

Tremor is one of the most predominant symptoms of patients with Parkinson disease (PD), but the underlying mechanisms for tremor relating to iron and its metabolism-related proteins and the inflammatory factors in cerebrospinal fluid (CSF) and serum have not been fully elucidated. A total of 135 PD patients were divided into a tremor-dominant (PD-TD) group ( = 74) and a postural instability and gait difficulty-dominant (PD-PIGD) group ( = 39) based on the ratio of mean tremor score to the mean bradykinesia/rigid score of the Unified Parkinson's Disease Rating Scale (UPDRS) III. Age and sex-matched healthy controls were recruited ( = 35). Demographic variables were evaluated; iron and its metabolism-related proteins and the inflammatory mediators in both CSF and serum were measured in these groups. The relevance of iron metabolism, inflammation and PD-TD were analyzed. (1) The PD-TD group had significantly decreased L-ferritin, increased iron levels in CSF and increased ferritin levels in the serum compared with the PD-PIGD and control groups ( < 0.05). (2) The PD-TD group had significantly enhanced IL-6 levels in both CSF and serum compared with the PD-PIGD and control groups ( < 0.05). (3) In CSF, the IL-6 level was increased as the iron level was elevated in the PD-TD group ( = 0.308, = 0.022). In serum, the IL-6 level was increased as the ferritin level was elevated in the PD-TD group ( = 0.410, = 0.004). The interplay between disturbed iron metabolism and relevant inflammation might modulate clinical phenotypes of PD.