Landgren O et al. (2008) Increased risks of polycythemia vera, essential thrombocythemia, and myelofibrosis among 24,577 first-degree relatives of 11,039 patients with myeloproliferative neoplasms in Sweden. Blood 112: 2199–2204

Myeloproliferative neoplasms (MPNs), including polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (MF), demonstrate familial clustering. A population-based, case–control study by Landgren et al. has quantified the risks of developing these malignancies for relatives of patients with MPNs.

The study included 6,217 patients with PV; 2,838 with ET; 1,172 with MF, and 812 with unclassified MPNs. In addition, 43,550 population-matched controls, 24,577 first-degree relatives of patients with MPNs and 99,542 first-degree relatives of controls were included. The authors showed that relatives of patients with MPNs had an increased risk of PV, ET and unclassified MPNs (relative risks 5.7, 7.4, and 7.5, respectively), although the risk of MF was not increased. Analyses conducted for first-degree relatives showed that siblings were at increased risk for development of MPNs. The mean age at diagnosis was not statistically different for affected relatives of controls and cases (60.6 and 57.5 years, respectively), which suggests that sporadic and familial MPNs have a similar age of onset. Moreover, the risk of developing MPNs according to age was not different between parents and offspring of the cases (P = 0.10). Relatives of MPNs patients had a borderline increased risk of chronic myeloid leukemia (relative risk, 1.9; P = 0.09).

These results show that relatives of patients with MPNs have a 5–7-fold increased risk of developing MPNs, and support the hypothesis that common susceptibility genes are involved in MPN pathogenesis.