Heamatological malignancies in giant cell arteritis: a French population-based study

Objectives. An increased risk of haematological malignancies (HM) has been reported in GCA patients. Our study aimed to investigate the incidence and the type of HM occurring in GCA. Methods. All patients with GCA and HM living in Cote d'Or (France) were identified by crossing data from the RHEMCO (Registre des He ` mopathies Malignes de Cote d'Or) and those having a positive temporal artery biopsy between 1 January 2001 and 31 December 2018. Results. Among 276 biopsy-proven GCA patients, 14 HM were identified in 12 patients (4.3%). In comparison with the general population aged >50 y, the incidence of myeloid HM and myeloproliferative syndromes were increased in GCA patients [standardized incidence ratios (SIR) = 2.71 and 5.16, respectively], with a specific increase in men with GCA (SIR = 4.82 and 9.04, respectively) but not in women. In addition, the study of SIR depending on the chronology between GCA and HM diagnoses suggests that there was an increased risk of developing GCA in men but not in women, after a diagnosis of myeloid HM (SIR = 9.56), especially if it was a MPS (SIR = 17.56). Conclusions. Our study shows a particular epidemiology of HM in GCA patients, which is characterized by an increased incidence of myeloid HM, especially MPS, in male GCA patients. The chronology of the diagnoses of GCA and HM raises the hypothesis that clonal hematopoiesis may be implicated in some cases of GCA.