Combined immunodeficiency due to RELA haploinsufficiency is a rare genetic disorder caused by a mutation in the RELA gene. This mutation results in a deficiency of the RELA protein, which is important for the development and function of the immune system. People with this disorder have a weakened immune system, which makes them more susceptible to infections. They may also have other health problems, such as recurrent infections, skin rashes, and digestive issues. Treatment typically involves antibiotics, immunoglobulin therapy, and other medications to help manage symptoms.