??? ??? ?? ? ? ?? ?? ??? ????? ??? ?? ??? ???? ??? ???? ?????.????? ??? ????? ???? ????.????? ???? ??? ??? ??? ???? ?????.A chromosomal abnormality consisting with the absence of one of the copies of chromosome 7 in somatic cells. [from NCI]By adolescence, all people with MLIV have extreme visual impairment. A neurodegenerative part of MLIV has gr