owing to the relationship between its lesions and those of other multiple malformation syndromes , notably those of the phakomatosis group , and to the possibility of borderline cases with these syndromes , or even with other dystrophies , such as williams-beuren dystrophia , the cardiovascular dysplasia of noonan 's syndrome must be classified within the vast group of histodysplasias which are embryonic diseases of the `` '' layers '' '' or `` '' neuro-ecto-mesodermoses '' '' of unknown genetic mechanism .
C0039082
syndromes
C0012634
diseases