Clinical laboratory characteristics and gene mutation spectrum of Ph‐negative MPN patients with atypical variants of JAK2, MPL, or CALR

Abstract

Abstract Objective To evaluate the incidence, clinical laboratory characteristics, and gene mutation spectrum of Ph‐negative MPN patients with atypical variants of JAK2, MPL, or CALR. Methods We collected a total of 359 Ph‐negative MPN patients with classical mutations in driver genes JAK2, MPL, or CALR, and divided them into two groups based on whether they had additional atypical variants of driver genes JAK2, MPL, or CALR: 304 patients without atypical variants of driver genes and 55 patients with atypical variants of driver genes. We analyzed the relevant characteristics of these patients. Results This study included 359 patients with Ph‐negative MPNs with JAK2, MPL, or CALR classical mutations and found that 55 (15%) patients had atypical variants of JAK2, MPL, or CALR. Among them, 28 cases (51%) were male, and 27 (49%) were female, with a median age of 64 years (range, 21–83). The age of ET patients with atypical variants was higher than that of ET patients without atypical variants [70 (28–80) vs. 61 (19–82), p = 0.03]. The incidence of classical MPL mutations in ET patients with atypical variants was higher than in ET patients without atypical variants [13.3% (2/15) vs. 0% (0/95), p = 0.02]. The number of gene mutations in patients with atypical variants of driver genes PV, ET, and Overt‐PMF is more than in patients without atypical variants of PV, ET, and Overt‐PMF [PV: 3 (2–6) vs. 2 (1–7), p < 0.001; ET: 4 (2–8) vs. 2 (1–7), p < 0.05; Overt‐PMF: 5 (2–9) vs. 3 (1–8), p < 0.001]. The incidence of SH2B3 and ASXL1 mutations were higher in MPN patients with atypical variants than in those without atypical variants (SH2B3: 16% vs. 6%, p < 0.01; ASXL1: 24% vs. 13%, p < 0.05). Conclusion These data indicate that classical mutations of JAK2, MPL, and CALR may not be completely mutually exclusive with atypical variants of JAK2, MPL, and CALR. In this study, 30 different atypical variants of JAK2, MPL, and CALR were identified, JAK2 G127D being the most common (42%, 23/55). Interestingly, JAK2 G127D only co‐occurred with JAK2V617F mutation. The incidence of atypical variants of JAK2 in Ph‐negative MPNs was much higher than that of the atypical variants of MPL and CALR. The significance of these atypical variants will be further studied in the future.

Keywords

• atypical variant
• classical mutation
• co‐existence
• driver genes
• myeloproliferative neoplasms