PCSK1 and endocrine system disorder: One of these variants, the N309K mutation in the PCSK1 gene, appeared to be the probable cause of the CDD and endocrinopathies, given that other mutations in PCSK1 are known to cause similar symptoms, whereas the other three variants (HADHA, FBXL17 and GTF3C2) are not known to be involved in CDD.