Based on quantitative reverse transcription PCR (RT–qPCR), the mRNA for DDX5, a component of spliceosome complexes9, but not all other tested splicing factors, including CDC5L, PRPF18, DHX8, DHX15, HNRNPA1 and SRSF1, was significantly decreased in whole skin lesions from patients with AD and psoriasis compared with healthy controls (Fig. 1a and Extended Data Fig. 1b). Here, PRPF18 is linked to psoriasis.