Is It Anthrax?

March 1, 2006
David L. Kaplan, MD

A 34-year-old woman awoke with apainful, crusted ulcer on her upperarm. She has been repairing dry wallin her home but recalls no trauma.The necrotic ulcer features an erythematousborder.

Case 1:
A 34-year-old woman awoke with apainful, crusted ulcer on her upperarm. She has been repairing dry wallin her home but recalls no trauma.The necrotic ulcer features an erythematousborder.

Is this anthrax?

Case 2:
Several days after a painful, progressivelygrowing lesion erupted on histhigh, a 68-year-old man seeks medicalcare. He has a low-grade feverand flu-like symptoms. There is nohistory of trauma or bite.

Cutaneous examination revealsan erythematous plaque with a centraleschar overlying a necrotic ulcer.

Anthrax or something else?

Case 1:
The sudden, overnightonset of the painful lesion led to thepresumptive diagnosis of brownrecluse spider bite. These arthropodsprefer dark, secluded areas, suchas behind walls and in attics andbasements, usually in the Midwestand Southwest.

Dapsone was prescribed. Within48 hours, the patient's pain abated,and the ulcer healed rapidly over thenext 10 days without sequelae.

Case 2:
The eruption on nonexposedskin and the lesion's large size areclues that this is not anthrax. Somestaphylococcal and streptococcal infectionscan be difficult to distinguishfrom early-stage anthrax.

Culture of the ulcer grew outStaphylococcus aureus, which confirmedthe diagnosis of ecthyma, anulcerative form of impetigo. This patient'sinfection responded slowly-but completely-to a long course ofa cephalosporin.

Case 3:
A 52-year-old woman with a history ofinflammatory bowel disease presentswith a painful lesion on her shin of afew days' duration. She reports notrauma or bite.

The erythematous plaque witha central, dusky, cyanotic, necroticappearingbulla is draining sanguineousfluid.

Anthrax or mimic?

Case 4:
Two days earlier, a painful lesion suddenlyappeared on a 49-year-oldwoman's thigh. The tender, erythematouspapule contains a central, crustedulcer. The patient has long-standingrheumatoid arthritis; there is no historyof trauma or bite.

Anthrax or look-alike?

Case 3:
The patient's history of inflammatory bowel disease heightened thesuspicion of pyoderma gangrenosum, which often occurs in persons withCrohn's disease or ulcerative colitis. Drainage from a bulla is not typical of anthraxlesions. A biopsy supported the diagnosis of pyoderma gangrenosum.Prednisone brought about a partial response; the skin disease completely resolvedfollowing a 2-week course of ciprofloxacin.

Case 4:
The pain and the patient'sunderlying connective tissue diseasereduced the likelihood of anthrax. Askin biopsy confirmed the suspecteddiagnosis of acute vasculitis, whichwas caused by a flare of the patient'srheumatoid arthritis.

A complete workup ruled outmore extensive internal involvement,such as kidney disease. Prednisonewas added to the patient's regimen ofNSAIDs; the arthritis responded tothis more aggressive systemic therapy,and the vasculitis resolved.

Case 5:
A 38-year-old importer of Asian rugs is concerned about an enlarging, red"bump" on her arm. She recalls no history of trauma but frequently has superficialabrasions from handling the carpets.

The patient reports that the lesion's central blister developed during thelast 2 days. The painless blister became black, and small lesions appearednear the original eruption.

Is this anthrax?

Case 6:
A 42-year-old woman presents with a2-day history of a painful lesion on thesuprapubic region. The central ulcerof the tender, erythematous plaque isdraining serosanguinous fluid. Shehas no history of trauma or bite.

What are you looking at here?

Case 5:
The clinical appearance of this lesion-a painless,black eschar surrounded by erythema and brawny,nonpitting edema-suggested cutaneous anthrax. Satellitevesicles can also occur. One of the patient's superficialabrasions probably provided a portal for Bacillus anthracis.

The diagnosis was confirmed by Gram staining andculture of the skin lesion; these positive results obviatedthe need for a skin biopsy, which must be performed whenthe culture and Gram stain are negative for B anthracis butclinical suspicion remains high.1

Doxycycline, 100 mg bid, or ciprofloxacin, 500 mgbid, is the recommended treatment. The recommendedduration of therapy has recently been extended from 7 to10 days to 60 days.2

Case 6: A bacterial culture grew outStaphylococcus aureus, confirming thediagnosis of folliculitis. The presentationof a painful, draining pustule orpapule around a hair follicle on nonexposedskin argues against anthraxand suggests folliculitis instead. Acephalosporin is appropriate inthis setting. This patient was givencephalexin, 500 mg tid, for 1 week.

Case 7:
This reddish, tender papule appeared on the arm of a 42-year-old woman 2 days after she had returned from acamping trip in Colorado. While hiking, she had sustainedseveral tick bites. She also has a low-grade fever and mildbody aches.

What does this look like to you?

Case 8:
A 58-year-old man presents with a nonproductive cough,low-grade fever, and a lesion on the dorsum of his righthand. The nontender, crusted ulcer first developed 2 or 3days ago; now an eschar overlies the necrotic ulcer. For afew years, the patient has been taking an iron-chelatingagent to treat iron overload.

Could this be anthrax?

Case 7:
The papule developed into avesiculopustule within a few days.The lesion then evolved into a necroticulcer that was covered with a blackeschar. The eschar was later shed,leaving a chancre-like lesion. A fewdays later, the patient's regional lymphnodes became tender and enlarged.

The results of Gram stainingand culture of the exudate, a punchbiopsy of the lesion, and serologic testingconfirmed tularemia. Francisellatularensis infection usually is contractedthrough broken skin from directcontact with an infected animal orfrom the bite of an infected flea or tick.Rarely, transmission occurs througheating infected meat.

Maintain universal precautionsin handling suspicious tissues or culture media; the organism is highly infectious.However, physicians are not thought to be at risk for contracting pulmonarytularemia from cutaneous lesions.

Aminoglycosides, macrolides, chloramphenicol, and fluoroquinoloneshave each been used successfully to treat tularemia.

Case 8:
The initial chest film was unremarkable; however, a second film obtained2 days later showed extensive interstitial disease. Culture of the affectedhand produced Zygomycetes fungi, which subsequently grew out on bloodcultures. Zygomycosis, or mucormycosis, was diagnosed. Iron chelation therapyis a risk factor for this infection.1

Despite aggressive therapy with intravenous amphotericin B, the patientdied 3 days later.




Ribes JA, Vanover-Sams CL, Baker DJ. Zygomycetes in human disease. Clin Microbiol Rev. 2000;13:236-301.

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