A 65 year old women has developed thick, erythematous nodules on her ears and nose with significant associated sensory loss. The nodules have grown slowly over the course of many years. Biopsy of the lesions shows dermal granulomas with giant cells but no acid-fast bacteria. Culture on blood agar and Lowenstein-Jensen medium shows no growth. These findings are most consistent with which of the following diagnoses?
Correct Answer: Tuberculoid leprosy
Description: Mycobacterium leprae is endemic to pas of Africa, Asia, and South America. Tuberculoid leprosy is an indolent disease, typically affecting cooler pas of the body, such as the nose and ears, producing dermal granulomas with very rare, acid-fast bacilli and damage to peripheral nerves. This is in marked contrast to lepromatous leprosy, which is progressive and invasive and generally characterized by the presence of numerous acid-fast bacteria in a histiocytic, but non-granulomatous tissue response. M. leprae has not been grown in any culture medium. Cutaneous leishmaniasis is due to Leishmania species that show a worldwide distribution. The infection is transmitted through a sandfly bite, and the skin lesion is typically ulcerated. Histology shows intracellular parasites within the dermis and epidermis. Granulomas are not formed. Onchocerciasis, or river blindness, is a roundworm infection transmitted by black flies of Africa and South America. The microfilariae grow at the site of inoculation, and cause an inflamed subcutaneous nodule. The organism is seen on tissue sections. Rhinoscleroma is a destructive granulomatous infection of the nasopharynx caused by Klebsiella rhinoscleromatis. Gram-negative rods can be cultured from the lesions. Ref: Ray C.G., Ryan K.J. (2010). Chapter 27. Mycobacteria. In C.G. Ray, K.J. Ryan (Eds), Sherris Medical Microbiology, 5e.
Category:
Microbiology
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