2/5/16 - Exam 3 Flashcards
List skin diseases (skin cancer, photodermatoses) caused by ultraviolet radiation.
Cancers caused by UVR:
Melanoma
Non-melanoma Skin Cancer like Basal Cell Carcinoma and Squamous Cell Carcinoma
Photodermatoses
-Idiopathic probably immunologic Solar urticaria, PMLE, actinic prurigo -DNA repair Defects
Xeroderma pigmentosum -Chemical photosensitivity
Drug induced
Porphyria -Photoaggrevated dermatoses
Psoriasis
Atopic Dermatitis
-Connective Tissue Disease Lupus Erythematosus
Dermatomyositis
Mixed Connective Tissue Disease
Be familiar with the function of the melanocyte, melanogenesis and melanin.
Melanocytes are known as honorary neurons. They have dendritic processes that interdigitate with surrounding basal and suprabasal keratinocytes.
Melanin is synthesized within intracellular organelles known as melanosomes. The process of melanin polymerization results in generation of free radicals that have the capability of damaging cells, hence the need for limiting melanin biosynthesis to melanosomes.
List Skin Defenses Against Ultraviolet radiation
- DNA Repair
- Apoptosis of Cells with DNA Damage
- Defenses Against Reactive Oxygen
- Melanin
Know which types of ultraviolet radiation cause various conditions (i.e. sunburn, photoaging, corneal burns etc).
Examination of the wavelengths that impact different types of skin damage after UV exposure shows that erythema (skin reddening) or sunburn is very similar to that observed for DNA damage and for non-melanoma skin cancer (NMSC). This observation suggests that UVB exposure results in DNA damage that plays a big role in development of NMSC. The other important observation is that both UVB and longer wavelength UVA are associated with incidence of melanoma. Recognition of this fact is critical in our understanding of the tanning salon industry that argues that UVA introduces a “protective tan”. UVA wavelengths are also the most effective at inducing reactive oxygen species (ROS) and immunosuppression.
Understand the composition and effects of solar radiation
The UV spectrum is divided into UV-C (100 - 280 nm), UV-B (280 - 320 nm), and UV-A (320 - 400 nm) radiation. The UV-C radiation as well as the radiation at shorter wavelengths is absorbed in the upper and middle atmosphere.
Define SPF, what increasing or decreasing SPF means, and the rationale for the use of sunscreen agents.
Sun Protective Factor refers to UVB rating
Describe vitamin D metabolism in the skin
-UVR (UVB) induces the non-enzymatic synthesis of cholecalciferol (VitD3) and ergocalciferol (VitD2). -Both converted to active form in liver and kidney
(Di-hydroxy Vitamin D3) is important systemic active form
-Dietary supplements contain VitD3 and vitD2 -Controversy regarding Vitamin D and cancer protection, and the need for ultraviolet induced Vitamin D
Discuss the role of ultraviolet radiation effects on the skin.
1) damage to DNA, RNA, lipids and proteins,
2) pro-inflammatory effects,
3) Immunosuppressive effects,
3) induction of innate defenses, 4) induction of apoptosis,
5) Vitamin D synthesis.
Melanocytes are known as
honorary neurons. They have dendritic processes that interdigitate with surrounding basal and suprabasal keratinocytes.
Review methods of skin cancer prevention
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Identify treatment options for premalignant and malignant skin tumors
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Know the difference in Breslow depth and Clark’s level used in staging of melanoma as important prognostic factors of melanoma
Breslow depth is recorded in millimeters with lesions less than 1.0 mm having an excellent prognosis with infrequent metastases and melanomas thicker than 4mm having a rather poor prognosis with a 5-year survival of approximately 50%.
Clark level, describes how far a melanoma has penetrated into the skin instead of actually measuring it. The Clark level of a melanoma uses a scale of I to V (with higher numbers indicating a deeper melanoma) :
§ the cancer stays in the epidermis (Clark level I)
§ the cancer has begun to invade the upper dermis (Clark level II) § the cancer involves most of the upper dermis (Clark level III)
§ the cancer has reached the lower dermis (Clark level IV)
§ the cancer has invaded to the subcutis (Clark level V)
Learn common mutations leading to skin cancer and chemotherapeutic interventions
- BCC = patch1 mutation, vismodegib
* Melanoma = BRAF mutation, vemurafinib
Understand that AKs are precursors to SCC
The actinic keratosis (AK) is the earliest identifiable lesion that can eventually develop into an invasive squamous cell carcinoma (SCC). One prospective study estimates that one AK/1000/year transforms into SCC, while retrospective studies predict that from 5-20% of all untreated AKs will progress to SCC. AK’s are typically produced by ultraviolet radiation, but ionizing radiation, arsenic, or polycyclic hydrocarbon exposure may also cause them. At least two prospective studies have demonstrated that sunscreen reduces the likelihood of developing more AKs. Actinic keratoses are distributed in areas of increased sun exposure and are characterized by hyperkeratosis and erythematous papules which are often easier to palpate than to visualize.
Identify risk factors for skin cancer
What youd think plus:
Gender
Men are 2 times as likely as women to have basal cell cancers and 3 times as likely to
have squamous cell cancers of the skin. This could be because they spend more time outdoors.
• Genetic Skin Diseases
o Basal Cell Nevus Syndrome
o Xeroderma pigmentosum
• Smoking
Smoking is a risk factor for squamous cell skin cancer, but not for basal cell cancer.
