Diseases of the skin vary from inflammatory disorders to highly malignant neoplasms. This chapter will discuss disorders of pigmentation, melanocytic proliferations (both benign and malignant), other pigmented lesions, non–melanocytic preneoplastic and neoplastic disorders, inherited skin neoplasia syndromes, acute and chronic inflammatory dermatoses, bullous diseases, other inflammatory skin diseases (including erythema nodosum), infectious disorders, and cutaneous manifestations of systemic disorders.
Overview: The three common disorders of pigmentation discussed below are vitiligo, freckles, and lentigo. These disorders represent predominantly cosmetic problems, but rarely may be mistaken for a premalignant lesion.
- Gross: Macules or patches of skin with loss of pigment.
- Areas affected: Hands, wrists, and perioral and anogenital regions.
Pathogenesis of vitiligo: Partial or complete loss of melanocytes, possibly of autoimmune etiology.
- Vitiligo versus albinism: Albinism is lack of melanin pigment due to genetic deficiency of tyrosinase.
- Vitiligo is associated with other autoimmune diseases, and is often seen in patients with Hashimoto thyroiditis, type 1 diabetes mellitus, or Addison disease.
Basic description: Hyperpigmented lesions occurring as a result of an increased amount of melanin pigment.
Important point: A freckle darkens with sunlight.
Basic description: Hyperpigmented lesions occurring as a result of an increased number of melanocytes along the basement membrane.
Important point: A lentigo does not darken with sunlight.
Overview: Melanocytic proliferations vary from the benign melanocytic nevus to the highly aggressive malignant melanoma.
Basic description: Benign proliferation of nevus cells, which are derived from melanocytes.
Types of melanocytic nevus
- Junctional nevus: Proliferation of nevus cells confined to the basal portion of the epidermis.
- Compound nevus: Proliferation of nevus cells at the basal portion of the epidermis and upper dermis.
- Intradermal nevus: Proliferation of nevus cells confined to the dermis (Figure 20-1).
Intradermal nevus. Note the proliferation of nevus cells within the dermis only, surrounding the skin appendages. As the nevus cells penetrate deeper into the dermis, they acquire a more “neural” appearance (arrow). Hematoxylin and eosin, 100×.
Microscopic morphology of melanocytic nevus: Nests of uniform round cells with inconspicuous nucleoli and few if any mitotic figures. As cells get deeper into the dermis, they acquire more of a neural appearance as a result of maturation of the cells.
Basic description: Proliferation of dysplastic nevus cells; dysplastic nevi are precursors of malignant melanoma.
Morphology of dysplastic nevus
- Gross: Variable pigmentation; > 5 mm in size; irregular borders.
- Microscopic: Fusion and coalescence of nests of ...
Log In to View More
If you don't have a subscription, please view our individual subscription options below to find out how you can gain access to this content.
Want remote access to your institution's subscription?
Sign in to your MyAccess profile while you are actively authenticated on this site via your institution (you will be able to verify this by looking at the top right corner of the screen - if you see your institution's name, you are authenticated). Once logged in to your MyAccess profile, you will be able to access your institution's subscription for 90 days from any location. You must be logged in while authenticated at least once every 90 days to maintain this remote access.
If your institution subscribes to this resource, and you don't have a MyAccess profile, please contact your library's reference desk for information on how to gain access to this resource from off-campus.
AccessPhysiotherapy Full Site: One-Year Subscription
Connect to the full suite of AccessPhysiotherapy content and resources including interactive NPTE review, more than 500 videos, Anatomy & Physiology Revealed, 20+ leading textbooks, and more.
Pay Per View: Timed Access to all of AccessPhysiotherapy
24 Hour Subscription $34.95
48 Hour Subscription $54.95
Pop-up div Successfully Displayed
This div only appears when the trigger link is hovered over.
Otherwise it is hidden from view.