Genotypic screening of the whole blood revealed compound heterozygous mutations in the CTSK gene (c.158delA, P.Asn53Thr/c.C830T, P.Ala277Val [Asn, asparagine; Thr, threonine; Ala, alanine; Val, valine]) (Fig. 3), but no mutation in the rearranged during transfection gene (RET) proto-oncogene associated with familial forms of MTC. The gene discussed is CTSK; the disease is medullary thyroid gland carcinoma.