Genetics · MU Sofia

53. Disorders of Sexual Development (DSD)

Explains disorders of sexual development as a discordance between chromosomal, gonadal and phenotypic sex, and sets out the three levels of normal sexual development. It then classifies the conditions by karyotype into sex chromosome, 46,XY and 46,XX groups, covering Turner, Klinefelter and mosaic forms, Swyer syndrome, androgen insensitivity, 17β-hydroxysteroid dehydrogenase deficiency and 21-hydroxylase deficiency. It ends with the diagnostic approach and a multidisciplinary management outline.

Inside: 8 sections · 7 labelled pictures · 15 flashcards · 4 min

Topic 53 of 65 in the MU Sofia syllabus for Genetics (Medicine, Year 3). The free AceMed note covers it in 8 sections, about 486 words (4 min of reading), with 15 flashcards.

In this note

  1. Disorders of Sexual Development (DSD)
  2. Normal Sexual Development
  3. II. CLASSIFICATION OF DISORDERS OF SEXUAL DEVELOPMENT
  4. III. SEX CHROMOSOME DSD
  5. IV. 46,XY DISORDERS OF SEXUAL DEVELOPMENT
  6. V. 46,XX DISORDERS OF SEXUAL DEVELOPMENT
  7. VII. DIAGNOSTIC APPROACH TO DSD
  8. VIII. MANAGEMENT PRINCIPLES

Disorders of Sexual Development (DSD)

Disorders of Sexual Development (DSD) are a group of congenital conditions in which there is discordance between chromosomal sex, gonadal sex, and phenotypic (anatomical) sex.

These disorders arise from abnormalities in:

  • sex chromosome constitution,
  • gonadal differentiation,
  • synthesis or action of sex hormones,
  • development of internal and external genitalia.

Normal Sexual Development

Sexual development proceeds through three sequential levels:

  1. 1. Chromosomal sex → established at fertilization (XX or XY)
  2. 2. Gonadal sex → differentiation into testes or ovaries
  3. 3. Phenotypic sex → development of internal and external genitalia

Disruption at any level results in a DSD phenotype.

II. CLASSIFICATION OF DISORDERS OF SEXUAL DEVELOPMENT

Modern classification is based on karyotype.

Main Categories

  1. 1. Sex chromosome DSD
  2. 2. 46,XY DSD
  3. 3. 46,XX DSD

III. SEX CHROMOSOME DSD

Disorders caused by numerical or structural abnormalities of sex chromosomes, affecting gonadal development.

Examples

  • Turner syndrome (45,X)
  • Klinefelter syndrome (47,XXY)
  • Mosaic karyotypes (45,X/46,XY)

Pathogenesis

  1. 1. Abnormal sex chromosome number.
  2. 2. Impaired gonadal differentiation.
  3. 3. Hormonal insufficiency.
  4. 4. Abnormal sexual development.

Clinical Features

  • Gonadal dysgenesis
  • Delayed or absent puberty
  • Infertility
  • Variable genital phenotype

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