F508del/L138ins compound heterozygotes do not have meconium ileus, CF-associated diabetes mellitus, severe liver damage and chronic Pseudomonas aeruginosa (Pseudomonas aeruginosa) infection is much less common than those who are homozygous for the most common pathogenic CFTR gene variant, F508del [19,20]. The gene discussed is CFTR; the disease is cystic fibrosis.