Mosaic variegated aneuploidy (MVA) syndrome is a very rare predisposition to mitotic non-disjunction leading to a high level of different aneuploid cells, which causes there to be cells with missing chromosomes (monosomy) or too many chromosomes (trisomy). Less than 15 patients have been described in the literature. Multiple different chromosomes and body tissues can be affected in the same individual and the proportion of aneuploid cells is usually more than 25%. Features of this condition include severe microcephaly, growth deficiency and short stature, mild physical abnormalities, eye abnormalities, central nervous system and brain abnormalities, seizures, developmental delay, and intellectual disability. The risk of cancer is high, with rhabdomyosarcoma, Wilm's tumor, and leukemia reported in several cases.
MVA is an autosomal recessive condition and is caused by changes (mutations) in the BUB1B gene, which encodes BUBR1, a key protein in the mitotic spindle checkpoint. During mitosis (the process of making new body cells), the spindle checkpoint helps to prevent too many or too little chromosomes separating into each new cell. Source: Genetic and Rare Diseases Information Center (GARD), supported by ORDR-NCATS and NHGRI.