Major histocompatibility complex class I chain-related genes (MIC) belong to a multicopy gene family located within the HLA class I region of chromosome 6. They encode for proteins that have a completely different organization, expression, and products from classical HLA class I gene products. One member of this family is the MICA gene, which is characterized by its high degree of polymorphism, with over 50 MICA alleles described. Moreover, MICA exon 5 presents a microsatellite polymorphism consisting of a variable number of GCT repeats that encode for 4, 5, 6, 9, or 10 alanine residues, and a variant (MICA A5.1) that includes a nucleotide insertion (GCT-->GGCT). In this study, we report a novel allele in the transmembrane region of the MICA gene consisting of seven GCT repeats found in a family based study of MICA polymorphism in celiac disease.