Dermclinic

April 2, 2009

The mother of this 6-year-old girl brings her to your office for evaluation of an itchy rash that started on her left cheek at the end of December. Another physician prescribed cephalexin for presumed impetigo; the rash abated but did not completely clear. During the past 2 to 3 weeks, new lesions have appeared on the child's neck, arms, and trunk.

Case 1:

The mother of this 6-year-old girl brings her to your office for evaluation of an itchy rash that started on her left cheek at the end of December. Another physician prescribed cephalexin for presumed impetigo; the rash abated but did not completely clear. During the past 2 to 3 weeks, new lesions have appeared on the child's neck, arms, and trunk.

 

 What do you suspect?

A. Impetigo with inadequate treatment course.B. Methicillin-resistant Staphylococcus aureus (MRSA) infection.C. Dermatophyte infection.D. Granuloma annulare.E. Contact dermatitis.

 

 

What action would you take?

F.Prescribe a different antibiotic.G. Order a bacterial culture.H. Perform a potassium hydroxide (KOH) examination.I. Perform a biopsy.
J. Perform patch testing.

 

 

 

(Answers on next page.)

Case 1: Tinea corporis

A KOH examination, H, showed a few sparsely scattered dermatophytes, C. The patient's mother volunteered that she and her husband had given their daughter 2 rats as a Christmas present the week before the rash developed.

 Impetigo and MRSA infections are usually tender rather than pruritic; moreover, impetigo should have responded to cephalexin. Granuloma annulare is typically asymptomatic. Because the child had no history of exposure to possible contactants, contact dermatitis was unlikely.

A 1-week course of oral terbinafine and a topical antifungal cream were prescribed for the child. Removal of the rats from the home was recommended. However, the family have become very attached to the animals and would prefer to keep them.

Bonus question: What treatment would be appropriate for the rats?    

(Answer on next page.)

Case 1: Tinea corporis

Answer to bonus question:

Washing the rats with an over-the-counter ketoconazole shampoo was recommended. In addition, oral terbinafine has been administered to rats at dosages of 20 to 400 mg/kg/d in clinical trials without adverse effects.

1

 

 

  

REFERENCE :
1. Walzer PD, Ashbaugh A. Use of terbinafine in mouse and rat models of Pneumocystis carinii pneumonia. Antimicrob Agents Chemother. 2002;46:514-516.

 (Dermclinic Case 2.)

 

Case 2:

For 6 years, a 71-year-old man has had these painful growths on his feet. He has tried various topical creams without success.

Which of the following would you include in the differential?

A. Plantar keratoderma.
B. Psoriasis.C. Dermatophyte infection.D. Lichen planus.E. Atopic dermatitis.F.Poor foot hygiene.

 

(Answer on next page.)

 

Case 2: Psoriasis

A skin biopsy confirmed the diagnosis of psoriasis, B. The other conditions in the differential were reasonable considerations that were excluded by the biopsy results.

What treatment would you offer?

G. Topical 40% urea cream.
H.
Potent topical corticosteroids.
I.
Topical calcipotriene or calcitriol.
J.
Topical tazarotene.
K.
Systemic treatment with an oral agent, such as acitretin or methotrexate, or an injectable biologic agent, such as etanercept.
L.
Referral to a podiatrist.

 

 

 

 

 (Answer on next page.)

Case 2: Psoriasis

All of the treatment options would be appropriate; however, the optimal approach is stepwise, with the topical medications as the first choices.

 

 

 

 

 

(Dermclinic Case 3.)

 

Case 3:

A 16-year-old girl presents for evaluation of urticaria that has occurred daily for the past several months. Recently, she has experienced occasional lip swelling but has had no difficulty in breathing. Antihistamines have not relieved her symptoms. Prednisone is the only treatment that seems to be effective. She is otherwise healthy.

 

Which of the following would you include in the workup?

 

A. Complete blood cell count.
B. Chemistry panel.C. Free thyroxine level.D. Free thyroid-stimulating hormone level.
E. Antinuclear antibody titer.
F. Erythrocyte sedimentation rate.

(Answer on next page.)

Case 3: Chronic urticaria

All of the laboratory studies would be reasonable to include in the workup. In this patient, the results of these studies were normal. Despite therapeutic trials of various oral antihistamines as well as montelukast, she again responded only to prednisone.

 What question would you ask this patient?    (Answer on next page.)

 

 

 


Case 3: Chronic urticaria and giardiasis

Inquiry about this patient's travel history revealed that she had been camping in Alaska. Subsequent testing showed a positive (1-3) ova and parasite examination. Treatment with metronidazole was successful.

 Giardia infestation has been associated with urticaria and angioedema.1

 

 

 

REFERENCE :
1. McKnight JT, Tietze PE. Dermatologic manifestations of giardiasis. J Am Board Fam Pract. 1992;5:425-428.

 (Dermclinic Case 4.)

 

Case 4:

 A 6-year-old girl presents with a flare of eczema, which had been stable for the past 2 years.

 Which of the following would you prescribe?

 A.Low-potency topical corticosteroid (eg, desonide).B.Mid-potency topical corticosteroid (eg, fluticasone).
C. High-potency topical corticosteroid (eg, fluocinonide).
D.Immunomodulator (eg, tacrolimus, pimecrolimus).
E.Over-the-counter anti-itch lotion.
F.Oral antihistamine.G.Oral prednisone.

 

(Answer on next page.)

Case 4: Eczema

This patient's flare did not resolve with the application of a mid-potency topical corticosteroid, B, and emollients.

What question would you ask this girl's parents?     

(Answer on next page.)

 

 

 

  

 

Case 4: Eczema and tinea corporis

On further questioning, the parents said that their daughter's best friend had received 2 rats as a Christmas present (see Case 1) and their daughter had been playing with the rats.

This patient was treated with a 1-week course of oral terbinafine as well as a topical antifungal cream, and the rash resolved.

 

 

 

 

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