Approximately 1/1000 apparently normal females has a 47,XXX (trisomy X) karyotype (1 Reference Approximately 1/1000 apparently normal females has a 47,XXX (trisomy X) karyotype ( 1). Advanced maternal age increases risk of trisomy X, and the extra X chromosome is usually maternally derived... read more ).
Advanced maternal age increases risk of trisomy X, and the extra X chromosome is usually maternally derived.
Physical anomalies are rare. Menstrual irregularity and infertility sometimes occur. Affected girls may have mildly impaired intellect and may have more school problems than siblings.
Although rare, 48,XXXX and 49,XXXXX females exist. There is no consistent phenotype. The risk of intellectual disability Intellectual Disability Intellectual disability is characterized by significantly subaverage intellectual functioning (often expressed as an intelligence quotient < 70 to 75) combined with limitations of adaptive... read more and congenital anomalies increases markedly when there are > 3 X chromosomes. The genetic imbalance in early embryonic life may cause anomalous development.
(See also Overview of Chromosomal Abnormalities Overview of Chromosomal Abnormalities Chromosomal abnormalities cause various disorders. Abnormalities that affect autosomes (the 22 paired chromosomes that are alike in males and females) are more common than those that affect... read more and see Overview of Sex Chromosome Abnormalities Overview of Sex Chromosome Abnormalities Sex chromosome abnormalities may involve aneuploidy, partial deletions or duplications of sex chromosomes, or mosaicism. (See also Overview of Chromosomal Abnormalities.) Sex chromosome abnormalities... read more .)
Reference
1. Skuse D, Printzlau F, Wolstencroft J: Sex chromosome aneuploidies. Handb Clin Neurol 147:355-376, 2018. doi: 10.1016/B978-0-444-63233-3.00024-5