PIK3CA and familial atrioventricular septal defect: The frequency of mixed disease in one ECD cohort is 19% [19] and BRAF V600E is a common driver in both diseases.[43] The discovery of concurrent PIK3CA and BRAF mutations in a proportion of ECD patients may be particularly relevant to our Pten-disrupted model.[44] However, most of the histocytes that accumulate in the spleen and lymph nodes of these mice are CD8+, unlike LCH cells.