By showing defective retrograde transport in patient-derived URECs and mutant IFT140 transfected CRISPR/Cas9-derived Ift140 knockout cells, we confirm the clinical and molecular diagnosis of SRTD9/Mainzer–Saldino syndrome in this patient. The gene discussed is IFT140; the disease is short-rib thoracic dysplasia 9 with or without polydactyly.