Using exome analysis and deep sequencing of genes on the X-chromosome, a mutation in CLIC2 (c.303C>G, p.H101Q) was discovered, which was found to be associated with X-linked intellectual disability (ID), atrial fibrillation, cardiomegaly, congestive heart failure (CHF), and seizures. The gene discussed is CLIC2; the disease is X-linked intellectual disability.