Cutis marmorata telangiectatica congenita (CMTC) is a cutaneous disorder often accompanied by additional anomalies, most commonly segmental overgrowth. Recently a clinically discrete condition has been described comprising CMTC and congenital macrocephaly together with pre- and post-natal macrosomia, segmental overgrowth, central nervous system malformations, connective tissue abnormalities and intellectual handicap. We describe the natural history of macrocephaly-CMTC (M-CMTC) syndrome in a further five patients including the oldest reported patient, a 22 year old. The addition of our five patients brings the total number of reported patients to 28 and now makes it possible to more accurately delineate the phenotype and the frequency of clinical manifestations. We add some further clinical associations to those previously described, including anomalies of the growth of hair and teeth, neuronal migration defects, dislocated hips and stridor. We discuss potential genetic mechanisms that might account for the pleiotropic manifestations of this apparently rare segmental overgrowth disorder.