Trace element and cytokine concentrations in patients with Fibrodysplasia Ossificans Progressiva (FOP): A case control study.

Fibrodysplasia Ossificans Progressiva (FOP) is a rare inherited disease characterized by progressive heterotopic ossification. Disease onset, severity and symptoms vary between FOP patients, as does the frequency and activity of so-called flare-ups, during which tendons, ligaments, muscle and soft tissue are replaced by bone. Traumata, infections or other stressors are known inducers of flare-ups, and the hormone Activin A may be involved in disease activity; however, reliable biomarkers for FOP activity are missing, and the basal trace element and inflammatory state of patients are unknown. We hypothesized that FOP patients develop characteristic deficiencies in inflammation-related trace elements and display a chronically increased inflammatory cytokine level, collectively aggravating disease course and flare-up risk. Serum samples from 15 FOP patients and 25 relatives were collected under highest quality standards. Concentrations of Cu, Se and Zn were determined by total reflection X-ray fluorescence, and 27 cytokines along with Activin A by specific antibody-based techniques. Data were tested for normal distribution and analyzed by parametric or non-parametric tests. Concentrations of Se and Cu were not different between the groups, while Zn levels were slightly higher in FOP as compared to controls (1110±251 vs. 970±176ng/ml, P=0.04). The average concentrations of cytokines and Activin A were not different. When focusing on the two patients with self-reported flare-ups, again no obvious differences were noted. The cytokines Eotaxin, G-CSF, hbFGF and TNF-α were within the upper half of measured concentrations, and may warrant further longitudinal analyses. Our data do not support the hypothesis that FOP patients display a characteristic pattern of trace elements or have a generally increased tone of pro-inflammatory cytokines.