Partial deletion of X chromosome syndrome initially have normal ovarian development in utero. Amenorrhea is the result of accelerated atresia of the follicles. The fibrotic ovaries are called streak ovaries.
In addition to gonadal failure, there are associated stigmata with Turner syndrome that include short stature, webbed neck, shield chest, cubitus valgus (increased carrying angle of the arms), low hair line, high arched palate, multiple pigmented nevi, and short fourth metacarpals (4). X inactivation is a process that inactivates most of the genes on one X chromosome. Of the genes on the X chromosome, 20% escape X inactivation, and it is believed that loss of the second copy of these genes in a 45,X patient causes the stigmata associated with Turner syndrome (5).
After the diagnosis of Turner syndrome is confirmed by karyotype, studies should be performed to ensure that cardiac (30% have coarctation of the aorta), renal (especially horseshoe kidney), and autoimmune (thyroiditis) abnormalities are diagnosed and treated.
Cardiac magnetic resonance imaging (MRI) should be used in addition to echocardiography (6). Evaluation should be performed in childhood to identify potential attention-deficit or nonverbal learning disorders. Women with Turner syndrome should be screened for diabetes mellitus, aortic enlargement, hypertension, and hearing loss throughout their lives (6).
Abnormal X Chromosome Those 46,XX individuals with partial deletions of the X chromosome have variable phenotypes depending on the amount and location of the missing genetic material. Patients with a deletion of the long arm of the X chromosome (Xq−) from Xq13 to Xq26 have sexual infantilism, normal stature, no somatic abnormalities, and streak gonads (7). Some patients may be eunuchoid in appearance and have delayed epiphyseal closure. Patients with a deletion of the short arm of the X chromosome (Xp) usually are phenotypically similar to individuals with Turner syndrome (8). Many genes on the Xp chromosome escape X inactivation and act similarly to genes on autosomes. The effective monosomy created by the deletion results in the phenotypic features of Turner syndrome (5). Most patients with a ring X have ovarian failure and phenotypes similar to Turner syndrome, although some are able to reproduce successfully. These patients differ from those with Turner syndrome in that they are more likely to have intellectual disability and have syndactyly. Patients with isochrome of the long arm of the X chromosome (i[Xq]) are similar to XO patients, with the exception that autoimmune disorders are more common. Half of the women with balanced translocations of the X chromosome to an autosome have gonadal failure. Typically, the normal X is inactivated to preserve the balance of autosomal genes. The gonadal failure can be caused by the chromosomal break occurring in a gene that is required for ovarian function, abnormal meiosis, or X inactivation of the translocated X and adjacent autosomal genes (5,9).
Mosaicism Primary amenorrhea is associated with various mosaic states, the most common of which is 45,X/46,XX (10). The clinical findings in 45,X/47,XXX and 45,X/46, XX/47,XXX are similar to those in 45,X/46,XX and vary in estrogen and gonadotropin production, depending on the number of follicles in the gonads. When compared with the pure 45,X cell line, individuals with 45,X/46,XX are taller and have fewer abnormalities, although 80% of those with 45,X/46,XX mosaics are shorter than their peers, and 66% have some somatic abnormalities. Spontaneous menstruation occurs in approximately 20% of these patients (10).