Although the frequency of the CT/TT (variant or ‘other’) allele of MTHFR CLCN6 gene at rs9651118 was high in our study compared to the CC (‘usual’) allele, there remained a significant association with KC development in a combined American and Irish cohort which may be of benefit in future studies on skin cancer in transplant recipients. Here, MTHFR is linked to keratoconus.