Despite the distinct underlying genetic defects: polycystin 1 and 2 (PC1 and PC2) for the most prevalent autosomal dominant PKD (ADPKD) and fibrocystin for a rapidly evolving “juvenile” autosomal recessive PKD (ARPKD), the malicious epithelial‐to‐cyst cell transformation is associated with a drastic switch in overall transport direction from predominantly reabsorptive to secretory (Belibi et al., 2004; Sullivan et al., 1998). The gene discussed is PKHD1; the disease is autosomal dominant polycystic kidney disease.