The most frequent variant in the whole population of MD and CD/CRD cases was the ABCA4 c.5882G > A, p.(Gly1961Glu), which recurred in 49 patients (34 MD and 5 CD/CRD), i.e. in 10.5% of all the screened alleles. The gene discussed is ABCA4; the disease is Cowden disease.