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This cheat sheet presents the main concepts of skin diseases
Typology: Cheat Sheet
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Definitions: Definitions (cont.): Skin Diagram: Major Skin Cells:
Viral Infections: Viruses are obligate intracellular organisms – metabolic basal cells. Human Papilloma Virus (HPV): DNA virus with numerous subtypes. Skin and oral mucosa causes squamous papillomas, verrucae vulgaris, verruca plantaris, verruca plana, condyloma acuminatum (genital warts) Molluscum contagiosum: DNA pox virus – umbilicated self- limiting lesion in children. Herpes virus: HVS1 and HPV (blistering vesicles), herpes zoster (chickenpox) and shingles. Human herpes virus 8 (HHV8): Kaposi’s sarcoma (HIV) Bacterial Infections: Impetigo: Staph.aureus in children but Strep. in elderly Celluliltis: Streptococcus pyogenes Tuberculosis of the skin (lupus vulgaris): Mycobacterium tuberculosis or Mycobacterium bovis the cause of scrofuloderma. Bacterial Infections: (cont) Leprosy (Hansen’s disease): Mycobacterium leprae (lepromatous and tuberculoid). Lepromatous form fatal while tuberculoid form destroy tissue and nerves resulting in mutilated leonine facies and auto- amputations of digits. Fungal and Protozoa Infections: Fungal: Common ringworm (tinea) Tinea pedis (athletes foot) Candida, Blastomyces and Norcardia Protozoal: Leishmaniasis infections transmitted by sandflies, organism infiltrates the macrophages Uticaria: Hives or wheals (reaction pattern), itching and swelling. Sudden marked increase in the permeability of the dermal blood vessels resulting in edema of the dermis – erythematous or edematous lesions. Histology: shows marked infiltrate of eosinophils and mast cells Uticaria: (cont) Causes: Plant and animal toxins, physical stimuli e.g. heat, cold or stress, various drugs (aspirin and antibiotics) Histamine is the mediator and increase in IgE. Lupus erythematosus (SLE or LE) -Autoimmune disease affecting connective tissue with antibodies directed against DNA. -Multisystem disease involving almost any organ, most common is skin and kidneys. -Epidermis and adnexa involved. -Skin only: Discoid lupus – erythematous, scaly and older lesions show hyperpigmentation. -Often symmetrical on the face with a butterfly rash over nose and cheeks, and on scalp it may cause scarring alopecia. -Immunofluorescence show IgG and IgM at the epidermal basement membrane – “lupus band test” Psoriasis: Genetically determined – HLA haplotypes (HLA Cw6, B13 and B17). Disease of epidermal proliferation and excess keratin production, driven by cytokines released from activated T-cells in the dermis Silver-grey scales of parakeratosis on extensor surfaces such as knees and elbows. First appearance may be at site of trauma e.g. surgical wound – “Koebner effect”. Result in destructive arthropathy (psoriatic arthritis) Small bleeding points – Auspitz’s sign. Histology: rete ridges becomes acanthotic with the dermal papillae covered by thin epidermis two or three layers thick. Loss of the granular cell layer. By AlbertEinstein Published 22nd March, 2018. Last updated 14th March, 2018. Page 2 of 5. Sponsored by Readability-Score.com Measure your website readability! https://readability-score.com
Squamous cell carcinoma (SCC): -Are common and usually caused by chronic UV exposure. -Other: immunosuppression, irradiation, chemical carcinogens, HPV infections and chronic infections. -More common in the elderly. -Rarely SCC arises at the edge of a chronic skin ulcer (Majolin’s ulcer). -Very aggressive and invasive however metastasize late. -Excision can be curative and SCC are more sensitive to radiation than BCC’s. Keratoacanthoma: Rapidly growing, cup-shaped squamous epidermal lesion Involves sun-exposed skin of elderly - face Keratoacanthoma: (cont) Regresses spontaneously if left untreated Histology: -Endophytic-endophytic squamous proliferation, -Cup-shaped lesion -Crater-like center filled with laminated keratotic material -Resembles a well differentiated squamous cell carcinoma Melanocyte Derived Lesions:
Melanocytes are pigmented cells Found in basal layer of epidermis Melanin is synthesized by melanosomes Found on skin and mucosal surfaces – oral cavity, vagina, conjunctiva etc. Types of Benign Lesions: Lentigos: Increase in single melanocytes in basal areas. Small, pigmented macule. Naevi: Increase in groups of melanocytes. Melanocytes form nests. Types of Benign Lesions: (cont) Freckle: Increase in melanin production by normal melanocytes which are taken up by adjacent keratinocytes. UV stimulation. Naevis: Common in light-skinned individuals. Absent at birth and appear in early childhood. Increase in number through early adulthood. Found mainly on sun-exposed areas. Different stages STAGE 1 - JUNCTIONAL: At dermo-epidermal junction –intraepidermal nests. Tan or brown pin-point macules (1- 2mm). Gradually enlarge. Increase in number of individual melanocytes at dermo-epidermal junction. STAGE 2 – COMPOUND: Nevus is elevated above skin surface. Childhood
adolescence.Slightly raised due to nests of melanocytes Naevis: (cont) STAGE 3- INTRADERMAL: Middle to old age. Nevus cells detach from dermo-epidermal junction. Smaller, more mature and less metabolically active. Cannot divide. Two components Junctional and intradermal. Pink due to lack loss of melanin Histology of Stage 2:
Melanoma (cont)
6mm
1 mm depth indicates significant risk for metastasis