Chronic mucocutaneous candidiasis (CMC) may be secondary to, for instance, HIV infection or steroid use, or there may be a primary immunodeficiency of genetic origin. Most cases of primary CMC are sporadic but both dominant and recessive inheritance has been described. Described gene mutations include those of the autoimmune regulator gene (AIRE) that causes the autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED) syndrome and the signal transducer and activator of transcription 3 gene (STAT3), causing the hyper-IgE syndrome. An autosomal dominant candidiasis-thyroiditis syndrome has been located to chromosome 2 and candidiasis with low expression of intercellular adhesion molecule 1 (ICAM-1) to chromosome 11. Now (New England Journal of Medicine 2009;361:1727–35; see also editorial, ibid: 1798–801) another gene mutation has been described in a large Iranian family with CMC. The study included 36 family members in five generations. Four living members had had recurrent fungal infections, three from early childhood. Three members of the family had died in adolescence, …