Pentasomy X is associated with short stature, intellectual disability, characteristic facial features, heart defects, skeletal anomalies, and pubertal and reproductive abnormalities.

Though significant disability is characteristic, there are so few diagnosed cases that confident conclusions about the presentation and prognosis remain impossible.

The major clinical features of pentasomy X are intellectual disability, short stature, facial and musculoskeletal abnormalities, and congenital heart defects.

[1] The overall portrait is one of moderate intellectual disability,[3] defined by an adult cognitive capacity similar to that of a six- to eight-year-old and the ability to acquire basic living and employment skills with support.

[3] Pentasomy X is associated with a number of physical anomalies, including short stature, clinodactyly (incurved pinky fingers), and distinctive facial features.

[9] The severity of repeated joint dislocations may lead to a differential diagnosis of Larsen syndrome, as suggested in one reported case.

[12] These findings are not specific to pentasomy X, but rather common to sex chromosome aneuploidies in general and in particular show a strong resemblance to the male counterpart 49,XXXXY.

[13] Epicanthic folds and hypertelorism are also observed in tetrasomy and trisomy X,[7] while clinodactyly and radioulnar synostosis are seen in all sex chromosome aneuploidies[1][14][15] and taurodontism is specifically common to X-chromosome polysomies.

[1] Some adolescents and adults with pentasomy X have been prepubertal,[1] while some have had premature ovarian failure (early menopause)[20] and some have had apparently non-noteworthy pubertal development.

The general profiles of the conditions are similar, with developmental delays, mild dysmorphic features, and shared congenital anomalies such as clinodactyly and radioulnar synostosis.

Both Turner's and pentasomy X are female-only disorders characterized by short stature, heart defects, and abnormal pubertal development.

[1] Though some reviews claim a poor prognosis due to the congenital defects observed in severe cases,[9] support groups report milder abnormalities than common in the medical literature, including adults with pentasomy X in fair health.

[3] The spectrum of severity varies; long-term support is consistent, though some women have been reported as being able to work part-time and manage some of their affairs.

[18] For sex chromosome tetrasomy and pentasomy disorders as a whole, good prognosis is linked to strong parental and personal support.

Girls and women with pentasomy X whose caregivers have acted as advocates for their success have been reported as achieving at higher personal and social levels than the general portrait of the medical literature.

[39] Pentasomy X was one of the later sex chromosome aneuploidies to be discovered, being preceded by Turner,[40] Klinefelter,[41] and trisomy X[42] in 1959, XXYY syndrome in 1960,[43] and XYY[44] and tetrasomy X[45] in 1961.

By the time of Linden, Bender, and Robinson's seminal review of sex chromosome tetrasomy and pentasomy in 1995, only 25 cases had been recorded, the eldest in a girl of 16.