CDKN2A and familial congenital mirror movements: At the somatic level, the very low frequency of disease-causing alterations (by mutation or inactivation by loss of expression) of the CDKN2A gene in sporadic CMM cases with allelic losses of 9p21 is again consistent with the presence of additional tumour suppressor gene(s) within this chromosomal area (Gonzalgo et al, 1997; Ruiz et al, 1998; Wagner et al, 1998).