They are also found in patients with biallelic hypomorphic mutations of RAG1 or RAG2 and combined immunodeficiency (Walter et al., 2015), in men with hemizygous mutations of FOXP3 and IPEX (Rosenberg et al., 2018), and in women with heterozygous null mutations of X-linked NEMO and incontinentia pigmenti (Bastard et al., 2020b). The gene discussed is FOXP3; the disease is incontinentia pigmenti.