The potential that the recognition of the presence of a rare disease in a founder population can lead to targeted therapies is exemplified by the CD55 variant in the Bukharian Jewish community, which can cause a spectrum of presentations from mild abdominal discomfort following a high-fat meal to a severe syndrome including protein-losing enteropathy, and is effectively treated by the complement C5-inhibitor eculizumab [28]. This evidence concerns the gene C5 and Protein-losing enteropathy.