Understanding the pain profile in patients with haemophilia: Impaired descending pain inhibition as measured by conditioned pain modulation

Introduction Haemophilic arthropathy is associated with pain that often becomes chronic, likely caused by peripheral and central mechanisms. In the field of haemophilia, to our knowledge, the role of the descending pain pathway, which can also be involved in these pain processes, has not been examined to date. Aim In light of the dearth of existing literature, we sought to evaluate the function of endogenous descending pain modulation in patients with haemophilia. Methods Thirty adult patients with moderate to severe haemophilia A or B (median [interquartile range] age 51.0 [42.0-54.0]) and 23 healthy adult controls (age 46.5 [36.8-54.3]) underwent conditioned pain modulation (CPM) in order to examine the function of endogenous pain modulation. The CPM response was determined by scoring a test stimulus (heat) alone as well as under the influence of a conditioning stimulus (cold) on the basis of a numeric rating scale (NRS) (0 = 'no pain' to 100 = 'worst possible pain'). Results Patients with haemophilia demonstrated a statistically significant reduced CPM response when compared with the age-matched healthy controls (median (interquartile range) NRS score: patients: -10 (-17.5-[-7.5]) vs controls: -20 (-30.0-[-13.75]); P = .002). The determined difference in the CPM response between both cohorts showed a medium effect size of r = .433. Conclusion The results of this study indicate that an impaired degree of endogenous pain modulation could be present in patients with haemophilia. Therefore, the function of the descending pain pathway should be considered regarding an individual and comprehensive pain management.