There are almost 2,000 different variants in the CFTR gene2 and up to 70% of CF patients contain at least one allele with a mutation at position 508 (c.1521_1523delCTT; commonly known as ΔF508), which results in the loss of Phe508 and disruption of the folding pathway of CFTR in the ER3. The gene discussed is CFTR; the disease is cystic fibrosis.