Disorders of the trunk

Psoriasis

• Peak onset in 20’s
• Can suffer explosive eruptions following strep pharyngitis, severe sunburn or in AIDS
• Stress and alcohol ingestion can cause exacerbations
• Steroid withdrawal, lithium, beta-blockers and anti-malarials can also cause exacerbations
• Well-demarcated, erythematous papules and plaques with silvery white scale
• Auspitz sign – Removal of plaque reveals minute bleeding points
• Tends to be symmetrical with predisposition for extensor surfaces
• Koebner phenomenon positive
• Guttate psoriasis – Scattered discrete lesions

Seborrhoeic dermatitis

• Midchest, axillae and groin involvement can occur
• Erythema with a greasy yellowish scale
• More severe in Parkinson’s, Down’s syndrome and AIDS

Pityriasis rosea

• Herald patch followed by generalised eruption in 1-2 weeks
  • Salmon coloured, 2-5cm wide, fine scaling (herald patch)
  • Christmas tree distribution
  • Collarette of scale with open edge on the inside of the lesion is pathognomonic
• Women > men
• 15-40yo
• HHV-6,7
• Spontaneously resolves in 4-12 weeks
• Treatment
  • Oral antihistamines, topical steroids (hydrocortisone 1%) and emollients

Tinea corporis

• Superficial dermatophyte infection
• Spreads via autoinoculation
• T. rubrum and T. mentagrophytes are most common
• Pets may harbour T. verrucosum and Microsporum canis
• Ringworm presentation with advancing scaling border (pathognomonic)
• Rx – Topical antifungals

Pityriasis versicolor

• Overgrowth of yeast Pityrosporum ovale (aka Malassezia furfur)
• Mostly in younger people during summer
• Asymptomatic hypo- or hyperpigmented coalescing, scaly macules
• Central upper chest and back most common sites
• Fine scale
• Treat with dandruff shampoo or topical clotrimazole

Lichen planus

• Constellation of 4 P’s: Purple, polygonal, papules and pruritis
• Violaceous flat-topped papules
• Typically on lumbar region, flexor wrists, pretibia, scalp and penis
• Koebner phenomenon seen
• Wickham striae – Fine, white, lacy reticulate lines that adhere to papules (looks like lichenification)
• 50% have mucous membrane involvement

Urticaria

• Transient pruritic wheal and flare
• Angioedema = Larger oedematous areas that involve superficial dermis and subcutanous tissue
• Lesions wax and wane over 24-48 hours
• Usually lasts <6 weeks
• Usually history of atopy
• Common triggers – Penicillin, sulfa drugs, food allergies, stings/bites, and infections
• Chronic urticaria (>6 weeks)
  • Usually trigger unknown but may be intolerant to NSAID’s, contrast, opioids, physical stimulation, cold, pressure, sunlight and cholinergic (exercise)
  • Dermatographism may be seen (firm stroking of skin leads to wheal)
• Rx – Antihistamines + oral steroids if severe angioedema or widespread urticaria

Pruritic urticarial papules and plaques of pregnancy

• PUPP
• Usually third trimester of first pregnancy
• Rarely occurs in subsequent pregnancies
• 1-2% of pregnancies
• No effect on outcomes
• Intensely pruritic, 1-2cm papules on abdomen and spread
• Face, mucous membranes, palms and soles are spared
• Usually resolves within 10 days of delivery
• Topical high potency steroids
• Oral antihistamines ARE NOT effective

Drug reactions

• Includes:
  • Morbilliform exanthems
  • Urticaria/angioedema
  • Acneiform eruptions
  • Photosensitivity
  • Lupus-like eruption
  • Hyperpigmentation
  • Fixed drug eruption
  • Vesiculobullous eruption
  • Lichenoid eruption
  • Skin necrosis (Warfarin, heparin)
    • Typically areas of high subcutaneous fat (buttock, thigh, breasts)

• Usually within 3 weeks of initiation (but not always)
• Morbilliform eruption
  • Most common
  • Diffuse, symmetric on trunk then spreads to extremities
  • Pruritis is common (vs. viral exanthem)
  • Antibiotics, bactrim most commonly
  • Amoxicillin in EBV especially common
• Urticaria/angioedema
  • Aspirin, NSAID’s, contrast, ACEi
  • Usually within 36 hours of exposure

• Lupus-like
  • Procainamide, phenytoin, hydralazine
• Acneiform
  • Beta-lactams, steroids, OCP, phenytoin, lithium, haloperidol
• Pigmentation
  • Zidovudine, phenytoin, OCP, amiodarone (gre—blue), antimalarials

• Fixed drug eruption
  • Tetracyclines, sulfas, NSAIDs, barbiturates
  • Solitary or multiple discrete round to oval erythematous patches that turn dusky red/violaceous
  • Mostly oral mucosa or genitals
• Lichenoid
  • May occur months after initiation
  • Gold, ACEi (captopril), beta-blockers, thiazides and NSAID
  • May take years to resolve after cessation of drug

Blistering diseases

• Vesicular
  • <1cm
  • Herpes, insect bite and allergic contact dermatitis
• Bullous
  • >1cm
  • Bullous pemphigoid, severe allergic contact dermatitis, SJS/TEN, bullous impetigo, necrotising fasciitis, vasculitis
• Pustular
  • White fluid-filled
  • Any blistering disease over time may become pustular
  • Primary pustular diseases include infection, acne and pustular psoriasis

Last Updated on October 13, 2021 by Andrew Crofton