Congenital FXIII deficiency arises from variants in the F13A1 (FXIII-A subunit) or F13B (FXIII-B subunit) genes, and classically presents with delayed umbilical stump hemorrhage, soft‐tissue and intracranial bleeding, impaired wound healing, and recurrent pregnancy loss. Here, F13B is linked to hyperinsulinemic hypoglycemia, familial, 4.