DEFINITIONS AND EPIDEMIOLOGY
The nomenclature, Disorders of Sex Development (DSDs), replaces the term “intersex,”1,2 to encompass various congenital conditions in which there is inconsistency between chromosomal, gonadal, and/or anatomical sex. Conditions with ambiguous external genitalia are included, encompassing atypical genital development. While this system (Table 6-1) allows the incorporation of new genetic and other information, the primary clinical advantage is a guideline for early diagnostic evaluation, approaching by phenotype and karyotype, to guide further etiological evaluation and management. This classification of diagnostic categories (Table 6-2) is limited because some conditions fail to fit into a single specific diagnostic category or fit into more than one category; for example, forms of gonadal dysgenesis may have a 46,XY, 46,XX, or 45,X/46,XY karyotype. This schema includes the genetic cause when known and allows for phenotypic variation within etiological categories. DSDs primarily include those conditions impacting reproductive or sexual function, while including variations of normal development such as mild hypospadias and idiopathic clitoromegaly. Even though a karyotype is used for initial categorization, the ideal current approach involves specific molecular etiologies, as genes are more specific, and would avoid the perception that sex is determined by chromosomes. For example, the presence of a Y chromosome may not be associated with consistent findings regarding factors important in determining sex assignment or assessing outcome, including fetal androgen exposure, genital masculinization, or germ cell development.
Table 6-1.Nomenclature: Disorders of Sex Differentiation1 |Favorite Table|Download (.pdf) Table 6-1. Nomenclature: Disorders of Sex Differentiation1
|Sex Chromosome DSD ||46,XY DSD ||46,XX DSD |
|45,X Turner syndrome ||Aberrant testicular development ||Aberrant ovarian development |
|47,XXY Klinefelter syndrome ||Disorders of androgen synthesis or action ||Disorders of androgen excess |
|45,X/46,XY Mixed gonadal dysgenesis ||Disorders of MIH synthesis or action ||Vaginal or uterine atresia |
|46,XX/46,XY Chimeric, ovotesticular ||Other ||Other |
Table 6-2.Examples of Diagnoses Using DSD Classification1 |Favorite Table|Download (.pdf) Table 6-2. Examples of Diagnoses Using DSD Classification1
|A. Sex chromosome DSD |
| 1. 45,X—Turner syndrome and variants |
| 2. 47,XXY—Klinefelter syndrome and variants |
| 3. 45,X/46,XY—Mixed gonadal dysgenesis, ovotesticular DSD |
| 4. 46,XX/46,XY (Chimeric, ovotesticular DSD) |
|B. XY DSD |
| 1. Disorders of testicular development |
| a. Complete gonadal dysgenesis (Swyer syndrome) |
| b. Partial gonadal dysgenesis |
| c. Gonadal regression syndrome |
| d. Ovotesticular DSD |
| 2. Disorders in androgen synthesis or action |
| a. Androgen biosynthesis defects |
| i. 5α-Reductase deficiency |
| ii. 17-Hydroxysteroid dehydrogenase deficiency |
| iii. StAR mutations |
| b. Defects in androgen action |
| i. Partial androgen insensitivity |
| ii. Complete androgen insensitivity |
| c. LH receptor defects (Leydig cell aplasia/hypoplasia) |
| d. Disorders of AMH (MIH) and AMH receptors (persistent müllerian duct syndrome) |
| 3. General categories |
| a. Hypospadias not associated with hormone defect |
| b. Cloacal exstrophy |
|C. 46,XX DSD |
| 1. Disorders of gonadal (ovarian) development |
| a. Ovotesticular DSD |
| b. SRY+, dup SOX9 testicular DSD |
| c. Gonadal dysgenesis |
| 2. Androgen excess |
| a. Fetal adrenal |
| i. 21-Hydroxylase deficiency |
| ii. 11-Hydroxylase deficiency...|
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