Fragile X affection (FXS), or Martin-Bell syndrome, is a abiogenetic affection which after-effects in a spectrum of appropriate concrete and bookish limitations and affecting and behavioral actualization which ambit from astringent to balmy in manifestation.
Frequency
Conservative estimates address that brittle X affection affects about 1 in 4000 males and 1 in 8000 females.
Pathology
The affection of brittle X affection are acquired by abnormalities in DNA on the X chromosome. Examination of the karyotype reveals a binding at the end of the continued arm of the X chromosome, followed by a attenuate fiber of abiogenetic material. The binding and attenuate fiber accord the actualization of a brittle allocation of the X chromosome. Sequencing of the abiogenetic actual reveals a repeating abject brace leash that is amenable for the syndrome.
Symptoms and Signs
People with brittle X affection accept physical, cerebral and behavioral abnormalities. They accept large, angled ears; a arresting button and forehead; a aerial angled palate; and, in postpubertal males, macroorchidism. The joints may be hyperextensible, and affection ache (mitral valve prolapse) may occur. Cerebral abnormalities may accommodate balmy to abstinent brainy retardation. Actualization of autism may develop, including adamant accent and behavior, poor eye contact, and amusing anxiety. Women may acquaintance menopause in their mid-30s.
Physical phenotype
Arresting aerial (one or both)
Continued face (vertical maxillary excess)
High-arched aficionado (related to the above)
Hyperextensible feel joints
Double-jointed thumbs
Flat feet
Soft skin
Larger testes in men
Low beef tone.
Transmission
Fragile X syndrome is an X-linked dominant condition with variable expressivity and possibly reduced penetrance.
Females have two X-chromosomes and thus have an increased probability of having a working FMR1 allele. Males with the fragile X cannot transmit it to any of their sons (since males contribute a Y-chromosome, not an X, to their male offspring), but will transmit the premutation to all of their daughters, as males contribute their X to all of their daughters. Males never transmit their full mutation (males with full mutations in their blood have premutations in their sperm), and expansion to full mutations never occurs through paternal transmission.
Females carrying one copy of the fragile X can transmit it to their sons or daughters; in this case each child has a 50% chance of inheriting the fragile X. Sons who receive the fragile X are at high risk of intellectual disability.
Diagnosis
Fragile X affection is frequently not doubtable until academy age or adolescence, depending on the severity of the symptoms. Boys with autism and brainy amentia should be activated for brittle X syndrome. DNA testing can ascertain aberrant DNA on the brittle X chromosome. The greater the cardinal of aberrant repetitions of DNA found, the added acceptable the adolescent will accept symptoms.
Treatment
Early intervention, including accent and accent analysis and anatomic therapy, can advice accouchement with brittle X affection to aerate their abilities. Stimulants, antidepressants, and antianxiety drugs may be benign for some children.
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