Dermatology

Pemphigus vulgaris can be fatal bc lesion within epidermis can cause bullae to pop and lose water and prone to infection. Therefore Pos nikolsky. Infect oral mucosa. Bullous pemphigoid doesn’t pop, bc lesion between epi and dermis. See linear under immuno imaging. Neg nikolsky.

Porphyria cutanea tarda see skin blisters from photosensitivity. Rx w phlebotomy. Associated w chronic hep C, iron overload, liver disease. Vs AIP which is guts and nuts (abd pain and psychosis).

Penicillin, sulfa drugs, rifampin, lamotragine can all cause skin rash:
Mobilliform rash, erythema multiforme, SJS, toxic epidermal necrolysis in order of severity. Mobilliform looks like measles. Erythema multiforme has many forms and small rings. SJS involves mucosa. TEN is nikolsky positive. Pemphigus vulgaris and scalded skin syndrome are also nikolsky pos.

Stevens Johnson syndrome you can die from lung epithelium sloughing off in lungs.

Dermatophytes rx: if involve just skin, use any topical Azoles. If involve nail or hair, use terbinafine or itraconazole, because oral. Terbinafine inhibit squalene epoxidase, inhibiting ergosterol synthesis. Accumulate in keratin. Azoles inhibit 14-alpha-demethylase in ergosterol synthesis.

KOH prep best for diagnosing fungal infection. But need culture to diagnose specific fungus. KOH melts away skin to reveal fungus.

Impetigo — infection of epidermis only. Treat with bacitracin or mupirocin bc topical. Aka bactroban.
Erysipelas — infection of epidermis and dermis.
Cellulitis — infects of subcutaneous tissue.

In general if don’t know what it is, rx skin infection w amoxicillin, dicloxicillin, naficillin, etc. which rx staph and strep.

Methicillin and griseofulvin is never the answer. Methicillin causes interstitial nephritis.

Necrotizing fasciitis is like cellulitis but has gas producing anaerobes. Add clindamycin and surgical debridement to management. Will die wo surg debridement.

Only do Tzank smear if you can’t tell what it is, like if looks like chancroid. Hsv you’ll see multinucleated giant cells.

Gonorrhea flows, hence the rrhea. No ulcers.

Rx HZV w Acyclovir. Acyclovir and ganciclovir both require thymidine kinase to be activated. Ganciclovir can also be activated by CMV kinase, which does not have thymidine kinase. Foscarnet is backup.

Imiquimod can treat verruca vulgaris by telling body to slough off the cell. Does not hurt or burn you, unlike other treatments.

Primary syphilis diagnose w dark field microscopy. VRDL not used bc chancre can resolve before formation of antibodies.
Secondary (systemic rash, condyloma lata) syphilis diagnose w VRDL.
Treat primary and secondary w IM penicillin. Tertiary w IV penicillin. If allergic, rx w doxycycline.

scabies. What makes you itch is hypersensitivity to scabies poop under your skin. Treat with Permethrin. Lindane works too but not as good.

toxic shock has shock (hypovolemia). Scalded skin only in skin. Both from staph.

Basal cell carcinoma. Shiny like a pearl. Biopsy and remove.

Kaposi Sarcoma is cuboidal epithelium w blood oozing its way thru hence redness. Caused by hhv8. Fix HIV and it will resolve.

Atopic dermatitis and psoriasis u can both use topical steroids, but prefer others bc ae. Atopic dermatitis (eczema) rx w antihistamines loratidine or fexofenadine, or immunosupp tacrolimus sirolimus. Psoriasis has antibody involvement so rx w mab (adalimumab, a TNF inh immunosupp) or vit a/d3 (calcipotriene) bc help maturation of cells. If wide area or systemic, use uv light. Last resort methotrexate bc liver fibrosis, or coal tar.

Seborrheic dermatitis (dandruff) is hypersensitivity rxn to fungus therefore rx w both steroid and antifungal.

Contact dermatitis like poison ivy…. Remove agent and give steroid if necessary.

Ptyriasis rosea looks like secondary syphilis except neg RPR and VDRL, and not on hands and feet like syphilis. Have herald patch. Cause unknown, but prob virus.

Body programmed to move every 90-120min at night to prevent decubitus ulcer. After 2-3 hrs skin can start to necrose.

Alopecia areata is autoimmune attack on hair follicles. Causes balding on areas. Rx by injecting steroids and hair will grow back. Associated w syphilis so also test VDRL.

Alopecia areata totals is total loss of all hair on body. Genetic and autoimmune.

Telogen effluvium: telogen means hair follicle. This is thinning of hair from being sick or on meds…body has better things to do than make hair.

Acne: rx first w antiseptic l benzoyl peroxide, then topical vitamin a (retinoic acid), then topical antibiotic l erythromycin or clinda, then oral antibiotic l minocycline (vs erythro which can give u diarrhea), then lastly oral retinoic acid derivatives l Accutane (isotretinoin) or tazarotene, teratogenic.