Derma 241120_155016 PDF - Skin Lesions & Diseases

# Merkel Cells: mechanoreceptor to light touch ## Skin Appendages - **Sweat**: - **Eccrine glands**: Thermoregulation, mostly in palms and soles. - **Apocrine glands**: Its function starts at puberty. Axilla, inguinal region. Part of pilosebaceous apparatus, discharges through hair orifice...

# Merkel Cells: mechanoreceptor to light touch ## Skin Appendages - **Sweat**: - **Eccrine glands**: Thermoregulation, mostly in palms and soles. - **Apocrine glands**: Its function starts at puberty. Axilla, inguinal region. Part of pilosebaceous apparatus, discharges through hair orifice. - **Sebaceous (fat) glands**: Found in body except palms and soles ## Primary Skin Lesions - **Macule**: Flat discoloration < 1cm - **Patch**: Flat discoloration > 1cm - **Papule**: Elevated solid lesion < 1cm - **Plaque**: Elevated solid lesion > 1cm, sometimes confluence of papules - **Nodule**: Elevated solid lesion > 1cm, has depth, large nodule is referred to as tumor - **Vesicle**: Collection of free fluid < 1cm - **Bulla**: Collection of free fluid > 1cm - **Pustule**: Collection of pus (leukocytes) & free fluid - **Whea (hivel):** Superficial pale swelling, surrounded by erythema. Lasts < 24h. Seen in urticaria ## Secondary Skin Lesions - **Scale**: Excess dead epidermal cells by abnormal keratinization and shedding - **Crust (scab)**: Collection of dried serum & cellular debris - **Erosion**: Focal loss of epidermis heals w/o scarring - **Ulcer**: Focal loss of dermis & epidermis. Heals w/ scarring - **Fissure**: Linear loss of dermis & epidermis, sharp, V shape walls - **Scar**: Abnormal formation of CT after injury /surgery. Can be atrophic/hypertrophic. # Diagnostic Skin Lesions - **Excoriation**: Erosion, linear, caused by scratching - **Comedone**: Pilosebaceous ductal hypercornification - **Blackhead**: Dilated opening - **Closed comedone**: Narrow - acne - **Milia**: Small keratin cyst w/o opening - **Cyst**: Circumscribed lesion w/ walled lumen - **Petechia**: Deposit of blood < 1cm - **Purpura**: Deposit of blood > 1cm - **Burrow (tunnel)**: Narrow tortuous channel produced by parasite sarcoptes scabie (scabies). - **Lichenification**: Thickening of epidermis induced by scratching, skin lines accentuated. - **Telangiectasia**: Dilated superficial blood vessels # Cutaneous Manifestations of Systemic Diseases ## 1. Diabetes Mellitus - Most common - 30% develop skin disorder: - **Necrobiosis lipoidica** - **Granuloma annulare** - **Acanthosis nigricans** ## **Necrobiosis Lipoidica** - 75% of pts with NL either have or will develop DM - Anterior surface of lower legs. - Oval, slow expanding patch, advancing red border, atrophic center - Ulceration easily occur after trauma - Small risk squamous cell carcinoma ## 2. Dyslipoproteinemia & Xanthoma - Lipid deposits in skin & tendons (xanthoma). - **Xanthelasma**: Most common form. Eyelids, atherosclerosis risk. - **Eruptive xanthoma**: Indication of hypertriglycemia! Papules on buttocks & limbs. - **Plane**: Palmar crease. - **Tuberous**: Elbows, knees. - **Tendinous**: Tendons on elbows/knees, Achilles tendon => persistent! ## 3. Neurofibromatosis - Skin, CNS, eyes, bones - Hamartomatous tumors surrounding nerves - **NF-1**: Most common - **NF-2**: Bilateral acoustic neuroma + other tumors - **NF-5**: Segmental # NF-1 Criteria - 7 Criteria, 2 of them enough for diagnosis. - 6 cafe au lait macules - Neurofibroma - Axillary freckling. - Lish nodules (melanocytic iris hamartoma) - Optic glioma - Osseous lesions - 1st degree relative w/ NF-1 - High lifetime malignancy risk.