Current treatments in the field of haemophilia are changing the phenotype of many patients with severe haemophilia to that of mild haemophilia. Although this has the potential to improve the quality of life of these patients, 1 many unmet needs remain in patients with mild-to-moderate haemophilia. Bleeding phenotypes in patients with mild-to-moderate haemophilia A, especially those with high-moderate haemophilia (factor VIII [FVIII] levels >2%), are variable; many patients only experience bleeding after trauma. 2 Therefore, these individuals may lack the ability to recognize a bleed and to self-infuse factor treatments, leading to musculoskeletal complications, including poor joint outcomes. Importantly, patients with mild-to-moderate haemophilia A or haemophilia B are often not included in or a focus of clinical trials 3 ; thus, there is a need for large, prospective studies to assess which patients could benefit from innovative treatments and to identify outcomes for this patient population. 2 | UNI QUE AT TRIBUTE S OF PATIENTS WITH MILD-TO-MODER ATE HAEMOPHILIA Patients with mild-to-moderate haemophilia possess several unique attributes, including a challenging diagnosis, variability in bleeding symptoms and treatment needs, and disease complications. Diagnosis of mild-to-moderate haemophilia A is often difficult, owing to significant variability in FVIII levels and bleeding symptoms. 4 Notably, the diagnosis may be missed or delayed as a consequence of normal screening test results. 3,5 Therefore, many patients with mild-to-moderate haemophilia are diagnosed at an older age than those with severe haemophilia; diagnosis usually occurs after a trauma or surgery. 4,5 In patients with moderate and severe haemophilia A, FVIII levels are generally concordant when measured by one-stage or chromogenic clotting factor assays. However, in approximately 30% of patients with mild haemophilia A, discrepancy in the one-stage and chromogenic assays may be seen. 6 This