EC Microbiology

Leprosy emerges as a contagious, chronic infectious disease engendered by Mycobacterium leprae. Lesions are preponderantly confined to cutis, peripheral nerves, mucosa of upper respiratory tract and ocular region. Lymph nodes are exceptionally involved. Infiltration of lymph nodes with lymph node enlargement is infrequent. Subjects demonstrate pyrexia, neurological symptoms as significant pain, palpable bilateral ulnar nerve, worsened palmoplantar esthesiometric examination, classical lesions of erythema nodosum or absence of pain. The intensely variable clinical representation is indicative of host immunological spectrum in response to Mycobacterium leprae infection comprised of Th1 and Th2 pattern of immune reaction [1,2]. Clinically, leprosy simulates diverse disease processes and expounds varied manifestations as numbness of extremities, non healing ulcer, repetitive ulcers, sensory loss or erythematous macules [1,2]. Localized pain with radiation, chills, insomnia, night sweats and spontaneous weight loss may ensue. Unilateral or bilateral lymphadenopathy may occur. Painless thickening of bilateral ulnar nerves and discrete infiltration of earlobes may be observed. Lepromatous leprosy expounds infiltration of spleen and hepatic parenchyma. Lymphoma may simulate or concur with lepromatous leprosy [2,3]. Besides, leprosy may simulate diseases as sarcoidosis, cutaneous lymphomas, Jessner’s lymphocytic infiltrate or connective tissue diseases [2,3]. Fine needle aspiration cytology (FNAC) of lymph node depicts foamy macrophages and poorly defined epithelioid cell granulomas [2,3]. Upon microscopy, lepromatous leprosy is comprised of lesions enunciating an infiltration of enlarged, pale, spherical histiocytes. An absence of epithelioid cell granulomas is encountered [3,4]. Alternatively, surgical tissue samples depict superficial ulceration, epithelioid cell granulomas and foamy macrophages. A distinct Grenz zone impregnated with acid fast bacilli of Mycobacterium leprae is observed. Necrosis is absent to minimal [3,4]. Discrete foci of perivascular inflammatory infiltrate with absent acid fast bacilli may be enunciated [3,4]. Infiltrated perilesional region is associated with epidermal rectification and a distinct Grenz zone expounding innumerable bacilli [4,5]. Disorganized dermal and perineural epithelioid cell granulomas are accompanied by an intense infiltrate of xanthomatous histiocytes impregnated with innumerable acid fast bacilli of Mycobacterium leprae. Morphologically, lymph node stroma is disorganized. Quantifiably significant histiocytes are observed. Absence of necrotic areas or infiltration of leukocytes may concur with lymph node reaction due to leprosy [4,5]. Leprosy induced lymph node involvement appears as a component of visceral disease observed in multi-bacillary subjects. The reticuloendothelial system expounds spectral infiltration by Mycobacterium lepra, akin to cutaneous lesions [4,5].

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12. Image 1 Courtesy: International Journal of Medicine.
13. Image 2 Courtesy: Leprosy review.