The hybrid transcripts from MB4-1 patients encode the full-length MMSET protein, while hybrid transcripts from MB4-2 patients lack the first translated exon of MMSET. MB4-3 patients lack the first and second translated exons of MMSET. The aim of this study was to clarify whether the overexpression of full-length (MB4-1) or truncated forms (MB4-2 and MB4-3) of MMSET influences the prognosis of MM patients with t(4;14). Here, NSD2 is linked to Miyoshi myopathy.