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Nummular dermatitis

May 22, 20252 min read

Case Five

Case Five: History

  • HPI: Kamil is a 35-year-old man who presents with three months of an extremely itchy red rash on his arms and legs.
  • PMH: seasonal allergic rhinitis, childhood eczema
  • Allergies: peanuts
  • Medications: loratadine
  • Family history: brother with asthma
  • Social history: lives with wife and two children
  • ROS: negative

  • Since this rash is scaly, you correctly start with a KOH exam, which is negative.
  • The round eczematous plaques are on his arms, legs, and back.
  • His scalp, umbilicus, nails, palms, and soles are unaffected.

Question 1

  • Mr. Kamil’s exam shows erythematous, coin-like, scaling, weeping, crusted plaques on his arms and legs. What is the most likely diagnosis?

    a. Guttate psoriasis (usually not weeping, crusted) b. Nummular dermatitis c. Pityriasis rosea (does not last this long, or weep) d. Secondary syphilis (does not last this long, or weep) e. Tinea corporis (KOH is negative, no central clearing)

Nummular dermatitis(discoid)

  • Nummular dermatitis presents as multiple coin-shaped eczematous plaques on the extremities and trunk
    • May be scaly but lacks the central clearing seen in tinea corporis and is KOH negative
    • Very pruritic
    • May exhibit weeping, cracking, vesicles, or crusts
    • Pathology shows spongiotic dermatitis

Now let’s look at a few examples of nummular dermatitis

Nummular dermatitis

Nummular dermatitis

Question 2

  • You diagnose Mr. Kamil with nummular dermatitis. What treatment would you recommend? a. Desonide cream (not strong enough) b. Clobetasol ointment (potent steroid) c. Oral erythromycin (for pityriasis rosea) d. Oral terbinafine (not fungal) e. Ultraviolet B (UVB) phototherapy (for guttate psoriasis)

Treatment

  • Treat like atopic dermatitis or any other eczema
  • Potent topical steroids are necessary to control this type of eczematous eruption
  • Apply emollients twice a day

Now, can you list four common causes of the papulosquamous eruption?

Try it before moving on to the next slide.

Papulosquamous eruption: differential diagnosis

  • Common causes:
  1. Tinea corporis
  2. Pityriasis rosea
  3. Psoriasis
  4. Nummular (discoid) dermatitis
  • Eruptions that do not fit the clinical description of one of these should be referred to dermatology

Graph View

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