High incidence of recurrent copy number variants in patients with isolated and syndromic Mullerian aplasia

Background Congenital malformations involving the Mullerian ducts are observed in around 5% of infertile women. Complete aplasia of the uterus, cervix, and upper vagina, also termed Mullerian aplasia or Mayer-Rokitansky-Kuster-Hauser (MRKH) syndrome, occurs with an incidence of around 1 in 4500 female births, and occurs in both isolated and syndromic forms. Previous reports have suggested that a proportion of cases, especially syndromic cases, are caused by variation in copy number at different genomic loci. Methods In order to obtain an overview of the contribution of copy number variation to both isolated and syndromic forms of Mullerian aplasia, copy number assays were performed in a series of 63 cases, of which 25 were syndromic and 38 isolated. Results A high incidence (9/63, 14%) of recurrent copy number variants in this cohort is reported here. These comprised four cases of microdeletion at 16p11.2, an autism susceptibility locus not previously associated with Mullerian aplasia, four cases of microdeletion at 17q12, and one case of a distal 22q11.2 microdeletion. Microdeletions at 16p11.2 and 17q12 were found in 4/38 (10.5%) cases with isolated Mullerian aplasia, and at 16p11.2, 17q12 and 22q11.2 (distal) in 5/25 cases (20%) with syndromic Mullerian aplasia. Conclusion The finding of microdeletion at 16p11.2 in 2/38 (5%) of isolated and 2/25 (8%) of syndromic cases suggests a significant contribution of this copy number variant alone to the pathogenesis of Mullerian aplasia. Overall, the high incidence of recurrent copy number variants in all forms of Mullerian aplasia has implications for the understanding of the aetiopathogenesis of the condition, and for genetic counselling in families affected by it.