Diagnosis And The Differential Diagnosis Of The Skin Lesions In Leprosy

Funom Makama By Funom Makama, 21st Mar 2014 | Follow this author | RSS Feed | Short URL http://nut.bz/201_3_g3/
Posted in Wikinut>Health>General Health>Diseases & Infections

Diagnosis of lepromatous leprosy is confirmed by the demonstration of M. leprae in the skin. A skin slit smear is prepared from the ear lobe or other areas by scraping the subepidermal tissue through a small incision. The material is stained by modified Ziehl Neelsen method.

Diagnosis Of Leprosy

For the proper diagnosis of leprosy, the following cardinal criteria should be insisted upon:
1. Skin lesions with sensory loss
2. Thickened nerve trunks; and/or
3. Demonstration of acid- fast bacilli in skin lesions by standard slit skin smears.

Other conditions that produce localized sensory loss are entrapment neuropathies and injury to peripheral nerves. It is a golden rule to consider thickened nerves as diagnostic of leprosy in endemic areas, unless proven otherwise. Rarely, nerves may be thickened in hypertrophic polyneuritis, Refsum’s disease, amyloidosis and traumatic neuromas.

Diagnosis of lepromatous leprosy is confirmed by the demonstration of M. leprae in the skin. A skin slit smear is prepared from the ear lobe or other areas by scraping the subepidermal tissue through a small incision. The material is stained by modified Ziehl Neelsen method. Quantitative estimation of the bacterial count is obtained by noting the density of the bacilli in the smear which is recorded as the bacterial index. Presence of many clumps of bacilli in an average field is recorded as 6+ whereas presence of 1 to 10 bacilli in hundred fields is recorded as 1+. In addition, the morphology of the bacilli enables the observer to assess their viability. This morphological index is used for recording progress with treatment. Nasal mucosa shows organisms and nasal smears give an idea of infectivity of the patient. In borderline leprosy M. Leprae are scanty and in tuberculoid leprosy, they are not present in the skin smears.

None of the cardinal diagnostic criteria like sensory changes, thickened nerves or organisms may be present in indeterminate leprosy. A high index of suspicion and familiarity with the early signs and symptoms are the only factors which help to diagnose this stage. Diagnosis has to be confirmed by the demonstration of M. leprae inside nerves or arrector pill muscle.

Differential Diagnosis Of The Skin lesions

Many other common skin conditions give rise to macular lesions. These are pityriasis alba, tinea versicolor, nutritional dyschromias, birth marks and early vitiligo. Raised lesions or plaques have to be differentiated from fungus infections, cutaneous tuberculosis, lupus erythematosus and lichen simplex. Psoriasis and lichen planus do not give rise to problems in diagnosis due to their distinctive features. Post-kala azar dermal leishmaniasis has to be distinguished from lepromatous leprosy. Reactions in leprosy may be mistaken for other forms of vasculitis as in systemic lupus erythematosus or polyarteritis nodosa.

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