In 20 of the analyzed patients, MCPH1 c.904_916del was the only deleterious mutation identified, whereas one unselected case (BR-0336, diagnosed with breast cancer at the age of 79 and melanoma at the age of 82, Table 2) carried also pathogenic mutation (rs80357571) in BRCA1. In this one case, the disease predisposition can be caused by either MCPH1 or BRCA1 mutation, or by their combined effect. The gene discussed is MCPH1; the disease is breast cancer.