Waardenburg Syndrome Overview
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Questions and Answers

What is the primary function of Merkel cells in the integumentary system?

  • Producing melanin for skin pigmentation
  • Stimulating hair growth
  • Facilitating the immune response in skin
  • Sensing pressure and deformation of skin (correct)

    • Which of the following correctly identifies one of the sources of mesenchyme that gives rise to the dermis?

  • Chorion
  • Dermatome (correct)
  • Ectoderm
  • Endoderm

    • At what gestational weeks do Merkel cells typically appear?

  • 16 to 20 weeks
  • 8 to 12 weeks (correct)
  • 4 to 6 weeks
  • 24 to 28 weeks

    • What type of cells are Langerhans cells classified as?

    <p>Mobile macrophage immune cells</p> Signup and view all the answers

    Which of the following is NOT a source of dermis formation according to the developmental origins?

    <p>Mesodermal Ectoderm</p> Signup and view all the answers

    What is the primary genetic cause of Waardenburg syndrome?

    <p>Mutations in the Pax3 gene</p> Signup and view all the answers

    Which feature is NOT commonly associated with Waardenburg syndrome?

    <p>Hyper-keratinization of skin</p> Signup and view all the answers

    What accounts for the deafness observed in Waardenburg syndrome?

    <p>Absence of melanocytes in the stria vascularis</p> Signup and view all the answers

    Which of the following best describes the inheritance pattern of keratinization defects?

    <p>Autosomal recessive or X-linked</p> Signup and view all the answers

    What is a common feature of ichthyosis vulgaris?

    <p>Mild, non-inflammatory scaling and dryness of skin</p> Signup and view all the answers

    Which pigmentation condition is directly linked to the absence of melanocytes?

    <p>Waardenburg syndrome</p> Signup and view all the answers

    What is the typical appearance of hair in patients with congenital alopecia?

    <p>Completely absent or very sparse</p> Signup and view all the answers

    What distinguishes atrichia from other hair loss conditions?

    <p>Absence of hair in any part of the body</p> Signup and view all the answers

    What condition involves the absence of a nipple?

    <p>Athelia</p> Signup and view all the answers

    When do peridermal cells shed during embryonic development?

    <p>18 weeks</p> Signup and view all the answers

    From which embryonic structure are melanocytes derived?

    <p>Neural crest cells</p> Signup and view all the answers

    What results from the persistence of fragments of the mammary line?

    <p>Accessory nipples</p> Signup and view all the answers

    What part of the skin do peridermal cells contribute to?

    <p>Stratum corneum</p> Signup and view all the answers

    Where is the dorsal dermis derived from?

    <p>Dermatome subdivision of somites</p> Signup and view all the answers

    What is the most severe form of ichthyosis?

    <p>Harlequin ichthyosis</p> Signup and view all the answers

    What is characterized by supernumerary nipples positioned along the milk line?

    <p>Polythelia</p> Signup and view all the answers

    What genetic condition is caused by a mutation in KREMEN 1, leading to ectodermal dysplasia?

    <p>Oligodontia</p> Signup and view all the answers

    Which process is influenced by Wnt signaling during skin development?

    <p>Epidermal commitment</p> Signup and view all the answers

    What characterizes the absence of pigment in the skin, hair, and eyes in albinism?

    <p>Inability of melanocytes to synthesize melanin</p> Signup and view all the answers

    What happens to ectodermal cells that do not respond to Wnt signaling?

    <p>They express BMP and develop into skin appendages</p> Signup and view all the answers

    What is the classification of cases with an absence or reduced amount of pigment specifically affecting skin, hair, and eyes?

    <p>Oculocutaneous albinism (OCA)</p> Signup and view all the answers

    Which of the following factors must be absent for ectodermal cells to express BMPs and commit to epidermal development?

    <p>Wnt signaling</p> Signup and view all the answers

    Individuals affected by which genetic disorder display depigmentation throughout their body?

    <p>Oculocutaneous albinism</p> Signup and view all the answers

    What is the primary role of KREMEN 1 in skin development?

    <p>Modulating Wnt signaling</p> Signup and view all the answers

    Which condition is described by an infant being encased in a translucent, taut, parchment-like membrane?

    <p>Collodion baby</p> Signup and view all the answers

    What is hypertrichosis characterized by?

    <p>Overgrowth of hair in various regions</p> Signup and view all the answers

    What are the modified sweat glands that develop from the mammary ridge called?

    <p>Lactiferous ducts</p> Signup and view all the answers

    What occurs in anonychia?

    <p>Complete absence of nails</p> Signup and view all the answers

    Which type of abnormality can cover the lumbar region particularly in association with spina bifida?

    <p>Hypertrichosis</p> Signup and view all the answers

    What is the primary skin appendage abnormality associated with overdevelopment of nails?

    <p>Anonychia</p> Signup and view all the answers

    Which condition involves epidermal changes characterized as epidermolytic hyperkeratosis?

    <p>None of the above</p> Signup and view all the answers

    What does the canalization of epithelial downgrowth in mammary gland development lead to?

    <p>Formation of alveoli and lactiferous ducts</p> Signup and view all the answers

    Study Notes

    Waardenburg Syndrome (WS)

    • Caused by defective neural crest cell migration and proliferation, resulting in loss of melanocytes.
    • Absence of melanocytes in the cochlea's stria vascularis leads to deafness.
    • Mutations in the Pax3 gene are primarily responsible for WS.
    • Key features include:
      • White patches in skin and hair, often found on the forelock.
      • Heterochromia iridis, or irises of different colors.
      • Hearing loss associated with loss of pigment cells.

    Congenital Alopecia

    • Characterized by hair absence on the scalp, eyebrows, and eyelashes.

    Ichthyosis

    • Group of hereditary disorders resulting in skin hyper-keratinization.
    • Inherited primarily as an autosomal recessive trait, but can also be X-linked.
    • Symptoms include non-inflammatory scaling, dryness, and deep fissures in the skin.
    • Types include:
      • Ichthyosis vulgaris (autosomal dominant): Mild form.
      • Lamellar Ichthyosis (autosomal recessive): Infants exhibit a "collodion baby" appearance.
      • Epidermolytic hyperkeratosis (autosomal dominant): More severe form.

    Hypertrichosis

    • A condition of excessive hair growth, localized or generalized.
    • Commonly seen over areas like the lumbar region, especially covering spina bifida occulta.

    Mammary Glands

    • Modified sweat glands that develop from the mammary ridge.
    • Formation involves epidermal downgrowth into the dermis, leading to the creation of alveoli and lactiferous ducts.
    • Ducts drain into the epithelial pit, forming the future nipple.

    Anonychia

    • Characterized by absent or underdeveloped nails that may occasionally show overdevelopment.

    Merkel Cells

    • Appear between the 8th to 12th weeks of intrauterine life.
    • Associated with free nerve endings and function as mechanoreceptors, sensing skin deformation.

    Langerhans Cells

    • Mobile immune cells in the skin, functioning as macrophages.

    Pigment Disorders

    • Albinism leads to absence or reduced melanin in skin, hair, and eyes.
    • Various types of oculocutaneous albinism exist due to inability of melanocytes to synthesize melanin.

    Molecular and Genetic Basis of Skin Development

    • Wnt signaling absence and FGF response influences ectodermal cell commitment to epidermal development.
    • Skin appendage development involves BMP signaling pathways.

    Breast Development Anomalies

    • Breast hypoplasia occurs when one mammary gland fails to develop, potentially resulting in the absence of a nipple (athelia).
    • Supernumerary nipples (polythelia) can develop from persistence of the mammary line.

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    Description

    This quiz delves into Waardenburg syndrome (WS), a genetic condition caused by mutations in the Pax3 gene. Key features include the defective migration of neural crest cells leading to absent melanocytes, resulting in white patches of skin and hair, as well as deafness. Test your knowledge on the characteristics and implications of this syndrome.

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