Acute myeloid leukemia (AML) with isolated trisomy 4 is rare. Associations with KIT mutations on chromosome 4q12 have been documented. The clinicopathologic features and mutational status of KIT, FLT3, NPM1, CEBPA, and RAS were assessed in 13 AML cases with isolated trisomy 4. There were 9 men and 4 women with a median age of 54 years. Median blast count was 84% (range, 24%-93%). Morphologic features varied across five 2008 World Health Organization categories. FLT3 (5/10) and NPM1 (4/10) mutations were observed at a frequency similar to normal-karyotype AML cases. KIT D816V (1/10), RAS (1/11; NRAS), and CEBPA (0/9) mutations were rare or absent. In 11 of 13 cases, complete remission was achieved. In 8 cases, relapse occurred, with median relapse-free survival of 11 months. Median overall survival was 28 months. AML with isolated trisomy 4 is rare and associated with high bone marrow blast counts and an intermediate to poor prognosis. KIT mutations are uncommon.