Combination therapy has been associated with the highest estimated incidence of IH, ranging from 7.7 to 10.5%, remarkably higher than monotherapy with anti-CTLA-4 (1.8–5.6%) or anti-PD-1 drugs (0.3–1.1%) (1, 18, 19, 20, 21, 22, 23). This evidence concerns the gene CTLA4 and isolated hemihyperplasia.