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Skin problems on the trunk

Author: Hon Assoc Prof Amanda Oakley, Dermatologist, Hamilton, New Zealand, September 2015.


Links to pages about skin conditions that favour the trunk.

Trunk: erythema without surface change

Erythema is less pronounced in dark skin.


  • Intermittent redness eg when hot, embarrassed or with certain foods
  • Often lifelong tendency
  • Systemically well
  • May precede/accompany rosacea


  • Sun-exposed site
  • Painful
  • Consider phototoxic drugs


  • Weals can arise on any site
  • Spontaneous and inducible types

Trunk: red papules/pustules

Acne vulgaris

  • Upper trunk
  • Open and closed comedones
  • Nodules + cysts if severe

Hot tub folliculitis

  • Bathing costume distribution
  • Exposed to hot tub
  • Papulopustules
  • Rarely, fever

Lichen planus

  • Lower back
  • Firm, violaceous papules + white streaks
  • Favours areas of earlier injury
  • Also examine mouth, distal limbs

Malassezia follicultiis

  • Upper trunk
  • Monomorphous superficial papulopustules


  • Mid trunk
  • Acute non-follicular papulopustules
  • Follows heat/sweating

Morbilliform drug eruption

  • Entire trunk spreading to limbs
  • Commenced new drug within 10 days
  • Monomorphic macules and papules
  • Variable itch

Trunk: erosions/crusting

Herpes zoster

  • Dermatomal
  • Painful
  • Erythema may precede vesicles
  • Culture/PCR: Herpes varicella zoster


Scabies rash

  • Burrows between fingers, wrists
  • Nodules in axillae, groin
  • Intense itch, especially at night
  • Dermatoscopy of burrow reveals mite

Transient acantholytic dermatosis / Grover disease

  • Acute or chronic
  • Itchy or asymptomatic
  • Elderly males
  • Crusted papules


  • Febrile illness
  • Also involves face, oral mucosa
  • Monomorphic eruption
  • Culture/PCR: Herpes varicella zoster

Trunk: dry/scaly + very itchy

May also blister, swell.

Allergic contact dermatitis

  • Acute flares on any site
  • Asymmetrical, odd-shaped patches/plaques
  • Patch tests positive

Atopic dermatitis

  • Patchy or diffuse
  • Acute flares are erythematous
  • Chronic eczema is lichenified

Nummular dermatitis

Secondary syphilis

  • Rash involves palms, soles
  • Positive syphilis serology

Trunk: dry and scaly with minimal itch

Annular erythema

  • Slowly enlarging rings
  • Scale just inside periphery

Pityriasis rosea

  • Distribution along Langers lines (fir tree pattern)
  • Larger herald patch appears several days before others
  • Oval shaped plaques with scale just inside periphery
  • Variable itch

Pityriasis versicolor

  • Mid-upper back and mid chest
  • Pale, pink or brown macules, patches
  • Diffuse bran-like scale
  • Mycology microscopy negative, culture positive


  • Roughly symmetrical distribution
  • Well-circumscribed erythematous scaly plaques
  • Variable itch

Seborrhoeic dermatitis

  • Mid-upper back and mid chest
  • Erythema, flaking
  • Skin feels rough on palpation
  • Often, follicular prominence

Subacute cutaneous lupus erythematosus

  • Upper trunk
  • Thin erythematous plaques
  • Peripheral scale
  • Check CBC, ANA, ENA
  • Biopsy confirmatory

Tinea corporis

  • Asymmetrical annular or discoid shaped plaques
  • Peripheral scale
  • Mycology microscopy + culture positive

Trunk: multiple skin coloured papules

Comedonal acne

  • Open and closed comedones
  • Folliculocentric

Granuloma annulare

  • Arranged in rings

Steatocystoma multiplex

  • Genodermatosis
  • Superficial pseudocysts

Pigmentary changes

Pigmentation is more pronounced in dark skin.

Postinflammatory pigmentation

  • Preceding eczema, psoriasis, acne etc
  • Distribution depends on cause

See also pigmentary disorders



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