๐ ็ธฝ็ฎ้ ๏ฝ ๐ ่ฑๆๅๆ๏ผๆฌ็ฏ๏ผ ๏ฝ ๐ ๅฎๆด็ฟป่ญฏ ๏ฝ โญ ็ฒพ่ฏ็ญ่จ
CUTANEOUS ANTHRAX
CUTANEOUS ANTHRAXย ย ICD-10: A22.000
โข Etiology. B. anthracis, a nonmotile, gram-positive, aerobic rod. Zoonosis. Spores can remain dormant in the soil for decades. Low-level germination occurs at the primary site, resulting in local edema and necrosis. Primary infection: Skin, pulmonary, and GI. Pathogenesis: Toxin mediated.
โข Transmission. Zoonosis of mammals, especially herbivores. Human infections result from contact with contaminated wild and domestic animals or animal products. Human-to-human transmission does not occur. At risk: Farmers, herders; slaughterhouse, textile workers.
โข Cutaneous anthrax. Accounts for 95% of anthrax cases in the United States.
โข Cut or abrasion on exposed sites of head, neck, extremities. Nondescript, painless, pruritic papule (resembling insect bite) appears 3 to 5 days after introduction of endospores. In 1 to 2 days, evolves to vesicle(s) ยฑ hemorrhage + necrosis. Vesicles rupture to form ulcers with extensive local edema (Fig. 25-46), ultimately forming dry eschars (1 to 3 cm). Satellite lesions can form in a nodular lymphangitis proximally on edematous extremity (Fig. 25-46).
โข Differential Diagnosis, Ecthyma, brown recluse spider bite, ulceroglandular tularemia, orf, or glanders.
โข Diagnosis. Isolation of B. anthracis from skin lesions, blood, or respiratory secretions, or by measuring specific antibodies in blood of persons with suspected symptoms.
โข Course and Treatment. Mortality rate in untreated persons with cutaneous anthrax is about 20%. Systemic penicillin is the drug of choice; alternatives are erythromycin, azathioprin, clarithromycin, or cephalosporins.
A
B
FIGURE 25-46 โข A cutaneous anthraxโA 40-year-old farmer with anthrax. (A) A black eschar at the site of inoculation with a central hemorrhagic ulceration on the thumb associated with massive edema of the hand. (B) A nodular lymphangitis extending proximally from the primary lesion on the thumb.