Gender differences in clinical presentations and sensory profiles in patients with fibromyalgia: implications of peripheral and central mechanisms.

Introduction: Fibromyalgia has a high female predominance and research work has been focussing mainly on women. Objectives: We aimed to answer (1) gender differences in pain scores and quality of life, (2) any gender-specific subgroups defined by quantitative sensory testing (QST), and (3) correlations of QST parameters with pain intensity and questionnaire scores. Methods: We evaluated clinical presentations and QST profiles from 38 male and 38 age-matched female patients. Results: Women reported significantly higher scores in average daily pain, daily sleep interference score, average weekly pain, weekly sleep interference score, and revised fibromyalgia impact questionnaire (rFIQ). Based on LOGA classification, L0G2, mechanical allodynia or hyperalgesia without abnormal sensory loss, was the most common QST subtype which accounted for 28.9% of men and 26.3% of women. Approximately 34.2% of men and 26.3% of women displayed loss of function of small fibres with an increased cold or warm detection threshold. Cold detection threshold was negatively correlated with pain intensity and functional impairment, suggesting a peripheral mechanism. Central sensitization, defined as allodynia and hyperalgesia to thermal or mechanical stimuli, was found in two-thirds of male and female patients. Mechanical pain sensitivity was positively correlated with the severity of pain and associated symptoms in women, but not men. Conclusion: There was a marked gender difference in reported pain and quality of life. We have confirmed that central sensitization is a major mechanism for women. Our data suggested an important role of small fibre pathology in both men and women.