Nummular Eczema and Fixed Drug Eruption

May 1, 2006

For the past few weeks, pruriticpatches have been erupting on a38-year-old man’s extremities. He recallsthat similar lesions occurredduring the last 2 winters. The patienthas a history of seasonal allergies;he owns a cat and 2 dogs.

Case 1:
For the past few weeks, pruriticpatches have been erupting on a38-year-old man's extremities. He recallsthat similar lesions occurredduring the last 2 winters. The patienthas a history of seasonal allergies;he owns a cat and 2 dogs.

Your clinical impression is . . .
A. Nummular eczema.
B. Ringworm.
C. Psoriasis.
D. Contact dermatitis.
E. Pityriasis rosea.

What action do you take?

F.

Perform a skin biopsy.

G.

Perform a potassium hydroxide evaluation.

H.

Recommend the use of mild soapsand moisturizers.

I.

Recommend that a veterinarianexamine the pets.

J.

Prescribe a corticosteroid cream.

Case 2:
A 39-year-old woman, who is being treated for a urinary tract infection, is concernedabout a red, slightly tender spot on her forearm. She recalls having hada similar lesion several years earlier. The patient has 2 cats.

What do you suspect?

A.

Superficial basal cell carcinoma.

B.

Nummular eczema.

C.

Fixed drug eruption.

D.

Tinea corporis.

E.

Contact dermatitis.

What course of action do you pursue?
F. Ask the patient about the medications she is taking.
G. Perform a skin biopsy.
H. Question the patient about the previous similar eruption.
I. Prescribe an antifungal cream.
J. Switch to another antibiotic for the urinary tract infection.

Case 1: Multiple, pruritic, coinshapedlesions that erupt during coldweather--particularly in personswith atopy--strongly suggest nummulareczema,A. Typically, only 1 or2 inflamed lesions occur when a petis the source of ringworm, which canbe ruled out by a potassium hydroxideevaluation, G.

The lesions of contact dermatitisusually are less well-defined andgenerally occur on exposed areas;because it was winter, this patient'sarms and legs had been covered.Pityriasis rosea arises on the trunk,and psoriasis affects the knees andelbows, which were clear in this patient.

The seasonal recurrence ofmultiple lesions is not a feature ofskin cancer; thus, a biopsy was notwarranted.The patient was advised to usea mild soap and to apply moisturizerassiduously, H, to his sensitive skin.The eczema responded quickly to atopical corticosteroid, J.

Case 2: Further questioning revealed that the patient was taking a sulfaantibiotic, F, for the urinary tract infection. She also remembered that theprevious eruption had occurred after she had been given a sulfa agent, H.This history supported the diagnosis of a fixed drug eruption,C-a circular,erythematous lesion that recurs at the same location after rechallenge withthe same drug. The original antibioticwas discontinued, and a nonsulfaagent was prescribed, J. If theeruption had not cleared, a biopsyto rule out skin cancer may havebeen appropriate.

The coin shape of this lesionsuggested nummular eczema, but itssolitary appearance and the absenceof pruritus ruled out that disease.Pruritus is characteristic of contactdermatitis and tinea corporis lesions,which are not transient or tender.

Case 3:
The parents of an 8-year-old boy seekevaluation of a red patch on their son'sshoulder. The asymptomatic spoterupted 2 weeks earlier. The patienthas seasonal allergies and frequentlyplays with his dog.

What does this look like to you?

A.

Psoriasis.

B.

Tinea corporis.

C.

Impetigo.

D.

Contact dermatitis.

E.

Erythema migrans.

What is your initial approach?

F.

Perform a skin biopsy.

G.

Perform a patch test.

H.

Perform a potassium hydroxideevaluation.

I.

Perform a bacterial culture.

J.

Recommend that a veterinarianexamine the dog.

Case 4:
For a few months, a 47-year-old man has noted a persistent,asymptomatic patch on his upper arm. The patienthas no significant medical problems, takes no medications,and has no history of seasonal allergies. He keeps apet cat and enjoys gardening.

Do you recognize this lesion?

A.

Nummular eczema.

B.

Basal cell carcinoma.

C.

Actinic keratosis.

D.

Pityriasis rosea.

E.

Tinea corporis.

What do you do now?

F.

Prescribe an antifungal antibiotic.

G.

Perform a potassium hydroxide evaluation.

H.

Perform a complete laboratory workup.

I.

Perform a skin biopsy.

J.

Observe and follow up in 3 months.

Case 3: A potassium hydroxide evaluation, H, confirmed tinea corporis,B,which responded to a topical antifungal. The family was advised to have theirdog examined by a veterinarian, J, since the pet was the suspected source ofthe dermatophyte.

Erythema migrans associated with Lyme disease was unlikely, since thepatient had no prodromal symptoms and the lesion developed in winter, far beyondthe tick bite transmission season. Because the single lesion was not pruriticand erupted on a site that was covered by clothing, patch tests for contactdermatitis were not warranted. The lesion demonstrated far less scale than isseen in psoriasis; the absence of tender, crusted vesicles ruled out impetigo.

Case 4: A skin biopsy, I, confirmedthe clinical suspicion of basal cell carcinoma,B. Because the patientworked shirtless every summer inhis garden, actinic keratosis was a diagnosticconsideration. The basal cellcarcinoma was excised completely,and the patient was instructed to usesunscreen when exposure to the suncould not be avoided.

This asymptomatic lesion wasneither pruritic nor scaly, thus rulingout nummular eczema and pityriasisrosea, respectively. Fungal infectionsgenerally are scaly and often pruritic;although they expand slowly, theydo so more quickly than basal cellcarcinoma.

Case 5:A 41-year-old man has been bothered by an itchy rash on his hands for severalweeks. The patient, a florist whose hands are frequently in water, has usedthe same moisturizer for years.

What has caused this condition?

A.

Psoriasis.

B.

Tinea manus.

C.

Lupus erythematosus.

D.

Contact dermatitis.

E.

Dyshidrotic eczema.

How would you confirm your diagnosis?

F.

Examine the patient's nails.

G.

Perform patch tests.

H.

Obtain an antinuclear antibody titer.

I.

Perform a skin biopsy.

J.

Perform a potassium hydroxide evaluation.

Case 6:

A 14-month-old boy presented with a 1-week history of a spreading, red rashon his left hand. He frequently sucks on the hand. The child is otherwisehealthy; there is no family history of seasonal allergies.

What is your tentative diagnosis?

A.

Impetigo.

B.

Candidiasis.

C.

Irritant dermatitis secondary to maceration and moisture.

D.

Dermatophyte infection.

E.

Herpetic whitlow.

How do you confirm your diagnosis?

F.

Perform a bacterial culture.

G.

Perform a fungal culture.

H.

Perform a viral culture.

I.

Perform a potassium hydroxide evaluation.

J.

Perform patch tests.

Case 5: Patch tests, G, not only confirmed contact dermatitis,D, but determinedthe culprit was African violets. A topical corticosteroid hastened resolutionof the outbreak. The patient now wears vinyl gloves when handlingthese plants.

Examination of the nails, F, did not reveal nail pitting, which is a hallmarkof psoriasis. Tinea manus features scaling, erythematous eruptions on thepalms that often spare the dorsa of the hands; this dermatophyte infection canbe ruled out by a potassium hydroxide evaluation. The rash of lupus erythematosususually involves the upper trunk and only the dorsa of the hands. Dyshidroticeczema is a chronic condition that features deep-seated vesicular eruptions,primarily on the palms and the sides of the fingers.

Case 6: A potassium hydroxide evaluation,I-the least costly and mostexpedient of the diagnostic procedures-confirmed candidiasis,B, andruled out a dermatophyte infection,which would be unusual in an infant.If necessary, a bacterial culture couldbe done to eliminate impetigo, whichmay resemble a Candida infection.

More severe redness and scalingis expected at the site of an irritantdermatitis secondary to macerationand moisture. The typical presentationof herpesvirus infection-groupedvesicles on an erythematous base-was not seen here.

A topical antifungal agent clearedthe candidiasis. To prevent the childfrom sucking on the treated hand, asingle coat of the agent was appliedafter he fell asleep for the night.