Dermatology Lecture Notes for USMLE

High-Yield Topics

Rash on Palms and Soles

• Mnemonic: TRICKS
  • T: Toxic Shock Syndrome
  • R: Rocky Mountain Spotted Fever
  • I: Infective Endocarditis
  • C: Coxsackie A
  • K: Kawasaki
  • S: Staphylococcal Scalded Skin Syndrome
  • S: Secondary Syphilis
• Infective Endocarditis: Janeway lesions on the palms

Erysipelas vs. Cellulitis

• Erysipelas: Raised, sharp borders, intense erythema (superficial)
• Cellulitis: Indistinct, non-sharp borders (deep infection)

Erythema Nodosum vs. Erythema Multiforme

• Erythema Nodosum:
  • Tender nodules, often on shins
  • Associated with IBD, sarcoidosis, medications
• Erythema Multiforme:
  • Target lesions
  • Associated with Herpes Simplex Virus

Lyme Disease

• Erythema Chronicum Migrans
• Treatment:
  • < 8 years: Amoxicillin

  • 8 years: Doxycycline

• Photosensitivity: Tetracyclines
  • Mnemonic: SAT (Sulfonamides, Amitriptyline, Tetracyclines)

Redman Syndrome

• Caused by Vancomycin and Ciprofloxacin
• Differentiate from sunburn via patient history

Skin Conditions Associated with Hepatitis C

• Porphyria Cutanea Tarda
  • Triggered by estrogens, ethanol
  • Treat with phlebotomy or hydroxychloroquine
• Lichen Planus
  • Five P’s: Purple, Poetic, Polygonal, Papules, Plaques

Herpes Zoster

• Reactivation of Varicella Zoster Virus
• Treatment: Acyclovir
• Risk Factors: Age, immunocompromised status

Dermatitis Herpetiformis

• Associated with Celiac Disease
• Treatment: Gluten-free diet, Dapsone

Tinea Versicolor

• Superficial fungal infection
• Treatment: Selenium sulfide, Ketoconazole, Terbinafen
• HIV increases risk

Pityriasis Rosea

• Begins with herald patch
• Lesions in Christmas tree pattern
• Treatment: Reassurance, antihistamines

Vitiligo

• Autoimmune destruction of melanocytes
• Associated with other autoimmune disorders

Skin Disorders & Associations

• Ash Leaf Spots: Associated with Tuberous Sclerosis
• Hidradenitis Suppurativa: Risk factors include smoking, diabetes, chronic stress
• Scabies: Type IV hypersensitivity

Pediatric Dermatology

• Mongolian Spots vs. Congenital Melanocytic Nevus
• Alopecia Areata: Autoimmune, treat with steroids

Acanthosis Nigricans

• Associated with insulin resistance, GI malignancy

Acne

• Treatment progression: Topical retinoids -> Topical antimicrobials -> Oral antibiotics -> Isotretinoin

Psoriasis

• Features: Silvery plaques, nail pitting, eye changes
• Trigger: Local skin trauma
• Treatment: Topical steroids, Vitamin D derivatives, Methotrexate

Dermatitis

• Seborrheic Dermatitis: Greasy scales
• Contact Dermatitis: Vesicles in exposed areas
• Atopic Dermatitis: Process of elimination

Skin Cancer

• Risk Factors: Sun exposure
• Melanoma: Use ABCDEs for diagnosis, excisional biopsy
• Basal Cell Carcinoma: Most common, treated with Mohs surgery
• Squamous Cell Carcinoma: Arises in chronic wounds, associated with keratin pearls

High-Yield Syndromes

• Nikolsky Sign: Positive in SJS/TEN, Staphylococcal Scalded Skin Syndrome
• Pemphigus Vulgaris vs. Bullous Pemphigoid: Differentiate by mucosal involvement, Nikolsky sign

Conclusion

• Comprehensive guide for USMLE dermatology prep
• Emphasize the importance of high-yield associations and mnemonics