Immunohistochemical staining of renal biopsy tissue samples showing positive MUC1fs staining in affected individuals with ADTKD-MUC1 and negative MUC1fs staining in controls. (A) Kidney section from a negative control at 10× magnification. (B) Negative control at ×40 magnification. (C) Kidney section from an individual affected by ADTKD-MUC1 at ×10 magnification, showing positive staining of the distal tubules and collecting ducts at ×20 magnification. (D) Kidney section from an individual affected by ADTKD-MUC1 at ×20 magnification, showing positive staining of the distal tubules and collecting ducts at ×20 magnification.