The good, the bad and the ugly of pain in haemophilia. Recent evidence on the epidemiology, molecular mechanisms and knowledge gaps preventing optimal treatment

Introduction: Haemophilia is an inherited, X-linked blood clotting disorder caused by the deficiency of coagulation factors VIII (FVIII, haemophilia A) or IX (FIX, haemophilia B). Spontaneous bleeds are common in severe forms of haemophilia and can also occur in moderate and mild haemophilia. Severe or repeated bleeding at a joint can evolve into chronic haemophilic arthropathy, with functional damage of the joint, disability, and intense chronic articular pain. Nonetheless, acute and chronic pain may emerge due to secondary conditions related to bleedings. Aim: This narrative review aims to critically discuss the most recent evidence about pain in haemophilia to give healthcare professionals a clear picture of current knowledge hence favouring the optimisation of clinical management of pain. Methods: Extensive literature search with the terms 'hemophilia' AND 'pain', focusing on the time window 2021-2023. Results: Acute and chronic pain is a critical aspect of haemophilia at all ages. It should be considered a multifaceted phenomenon, with a positive role as an early emergency signal of a clinical event (haemarthrosis), and numerous detrimental aspects linked to its burden that heavily affects the health-related quality of life, with psychological and social consequences. Conclusion: Despite its prevalence and frequency in people with haemophilia, pain is often underestimated by healthcare professionals, leading to insufficient and inadequate treatment, also due to uncertainty linked to the presence of the coagulation disorder or arthritic flares.