Pathogenic variants in RAC1 cause the autosomal dominant inherited intellectual developmental disorder type 48 (OMIM # 617751), while heterozygous pathogenic variants in CDC42 can cause Takenouchi-Kosaki syndrome (OMIM # 616737). Here, RAC1 is linked to macrothrombocytopenia-lymphedema-developmental delay-facial dysmorphism-camptodactyly syndrome.