Turner's syndrome

(Harry Turner, 1892 - 1970, American endocrinologist), (also called ovarian agenesis, gonadal dysgenesis, gonadal agenesis or gonadal aplasia), a rare inherited chromosomal disorder of females characterized by short stature and absence of sexual development at puberty. Other physical features may include a webbed neck, heart defects, kidney abnormalities, and various other malformations such as coarctation of the aorta, and abnormalities of the eyes and bones. It affects 1 in 3,000 live births. Normally, females have two X chromosomes. In some cases of Turner's syndrome, however, one X chromosome is missing from the cells (45,X); research studies suggest that approximately 40% of these individuals may have some Y chromosomal material in addition to the one X chromosome. In other affected females, both X chromosomes may be present, but one may have genetic defects. In still other cases, some cells may have the normal pair of X chromosomes while other cells do not (45,X/46,XX mosaicism). Although the exact cause of Turner's syndrome is not known, it is believed that the disorder may result from an error during the division (meiosis) of a parent's sex cells.

The most common karyotypic abnormality is 45, XO. It is estimated that the majority (perhaps as high as 95%) of conceptuses with monosomy X are miscarried. A substantial number of patients, however, are mosaics, with several cell lines. Because mosaics do not completely express the classic phenotype, there is a wide range of clinical findings. However, streak ovaries and sexual infantalism are classic findings. At puberty, there is failure to develop normal secondary sex characteristics. The genitalia remain infantile, breast development is inadequate, and there is little pubic hair. The gonads in Turner's syndrome fail to develop normally and appear as white streaks located where the ovaries would normally be. Fibrous tissue, microscopically indistinguishable from that of the normal ovarian stroma, is the major component of the streak, which consists of an attenuated cortex, a medulla, and a hilus. The cortex is composed of characteristic ovarian stroma. Rete tubules (rete ovarii) and hilar cells are typically present in the hilus region.

The main role for imaging is usually in the evaluation of the hypoplastic and infantile Mullerian duct derivatives, such as the uterus which is small in size. MRI images can also demonstrate low signal intensity with indistinct zonal anatomy of the uterus. Ovarian streaks are seen as very small, often linear to oval adnexal structures which on MRI T2-weighted images have low signal intensity.

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