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Dermatophyte Infection and Brown Recluse Spider Bite


A painful necrotic lesion, a pruritic rash that recurs after corticosteroid therapy, an ulcer on the tongue-do you recognize the disorders pictured here?

Case 1:

A 73-year-old man presents with an itchy rash that developed 4 months earlier on his forearm. Previous treatment with tapering courses of prednisone and application of a topical corticosteroid cream resolved the rash, but it recurred when the medications were discontinued. The patient is otherwise healthy.

What do you suspect?


Contact dermatitis to the patient's watch or watchband.


Dermatophyte infection.






Cutaneous lupus.

(Answer on next page.)

Case 1: Dermatophyte infection

A positive potassium hydroxide (KOH) examination confirmed the suspected diagnosis of dermatophyte infection, B. The patient was successfully treated with a topical antifungal cream. In some cases, however, an oral antifungal agent is needed.

Contact dermatitis should have resolved following prednisone and corticosteroid therapy unless the patient was being re-exposed. Moreover, the area involved was too broad to be the result of contact with his watch or watchband.

Eczema is unusual in a man of his age, and it would be rare for eczema to be confined to the forearm. Neurodermatitis would be a reasonable diagnostic consideration if the KOH examination had been negative. Lupus could manifest on the forearm (the left forearm is a more common site than the right one in patients with lupus who drive a great deal), although it tends to be more erythematous and more indurated than this patient's rash.

Case 2:

For 1 week, a 56-year-old physical therapist has had a worsening painful lesion on the back of one calf. He has no history of recent trauma, and he is otherwise healthy.

What is your clinical impression?



Staphylococcus aureus

(MRSA) infection.


Brown recluse spider bite.


Dermatophyte infection.


Cutaneous vasculitis.



(Answer on next page.)

Case 2: Brown recluse spider bite

Culture results were negative, and oral antibiotics, which were given for about 1 week pending the results of the culture, had no effect on the lesion. In fact, the patient's condition worsened during this period. He was then given dapsone for a presumptive diagnosis of brown recluse spider bite, B, and within 48 hours the pain resolved. The lesion subsequently healed uneventfully over several days without any sequelae or recurrence.

MRSA should grow out on culture and respond to appropriate antibiotics. Dermatophyte infections are typically pruritic, not tender or ulcerated. Vasculitis is a possibility, although this patient had no underlying disease or other manifestations of vasculitis. Ecthyma is usually bacterial in origin and can be identified on culture.

Case 3:

A 55-year-old woman presents for evaluation of an asymptomatic eruption of a few months' duration on the dorsa of both hands. She is essentially healthy and has started no new medications recently.

Which of the following would you include in the differential?


Granuloma annulare.


Tinea corporis/manus.


Cutaneous larva migrans.


Actinic granuloma.


Polymorphous light eruption.

(Answer on next page.)

Case 3: Actinic granuloma

A biopsy confirmed the diagnosis of actinic granuloma, D. This dermatoheliosis is induced by chronic sun exposure that breaks down the elastin, producing an immune response to the altered elastic fibers. Topical corticosteroids are effective treatment. Advise affected patients that daily application of sunscreen is mandatory.

Granuloma annulare, A, is a possibility, but a biopsy would rule out this condition. Tinea is scaly and pruritic. Both cutaneous larva migrans and polymorphous light eruption are more pruritic and erythematous than the eruption seen here.

Case 4:

For several days, a 57-year-old man has had a painful ulcer on the side of his tongue. He had a similar episode 1 year earlier that eventually resolved. He is otherwise healthy.

Which of the following statements about this patient's condition is/are false?


There is evidence of a genetic predisposition.


This condition is associated with iron deficiency.


This condition is associated with vitamin B




This condition is associated with folate deficiency.


Several studies have linked this condition with herpes simplex virus.

(Answer on next page.)

Case 4: Aphthous stomatitis

Recurrent aphthous ulcers are associated with hematinic deficiencies, including iron, folate, and vitamin B12. There is evidence of a familial occurrence with this condition. However, numerous studies have failed to demonstrate any microbial association, E.1-3




Miller MF, Garfunkel AA, Ram C, Ship II. Inheritance patterns in recurrent aphthous ulcers: twin and pedigree data.

Oral Surg Oral Med Oral Pathol.



Koybasi S, Parlak AH, Serin E, et al. Recurrent aphthous stomatitis: investigation of possible etiologic factors.

Am J Otolaryngol.



Sciubba JJ. Oral mucosal diseases in the office setting-part I: aphthous stomatitis and herpes simplex infections.

Gen Dent.



• Scully C, Gorsky M, Lozada-Nur F. The diagnosis and management of recurrent aphthous stomatitis: a consensus approach. J Am Dent Assoc. 2003;134:200-207.

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