A novel germline JAK2 splice-site variant causing exon 10 skipping in a patient with clinically diagnosed essential thrombocythemia and early-onset tophaceous gout: a case report

Triple-negative essential thrombocythemia (ET) lacks canonical driver mutations, and its molecular basis remains largely undefined. A 26-year-old man presented with early-onset tophaceous gout and persistent thrombocytosis. Screening for JAK2 V617F, CALR and MPL was negative; extended sequencing identified a novel JAK2 splice-site variant (c.1326+2T>A), and RT-PCR confirmed complete exon 10 skipping, generating a truncated transcript predicted to retain the FERM domain—a configuration resembling recently reported germline JAK2 drivers of hereditary thrombocythemia.