Clinical Review
and therefore leprosy can mimic other skin diseases leading to incorrect diagnosis. Multiple and giant patches are associated with the ‘borderline’ forms of the disease. Leprosy can also present with diffuse skin thickening associated with hair loss or multiple flesh- coloured or erythematous papules and nodules: these clinical presentations are characteristic of ‘lepromatous’ or multibacillary leprosy, which is associated with poor cell-mediated immunity to M leprae and is significantly more infectious than paucibacillary leprosy (see Figure 2). Whenever leprosy is suspected the patient should be completely undressed in order to look for any other signs that might provide further clues to the diagno- sis: visible enlargement and thickening of peripheral nerves should be actively sought, in particular that of the greater auricular (see Figure 2), radiocutaneous, and posterior tibial nerves; the presence of neuropathic ulcers is indicative of established nerve damage; and male patients may have testicular atrophy and gyneco- mastia secondary to hypogonadism although this is rare. A full motor and sensory assessment is important to es- tablish whether nerve involvement has resulted in motor and sensory impairment such as wrist drop (radial nerve damage) or foot drop (common peroneal nerve dam- age), claw hand (ulnar and median nerve damage) (see Figure 3) or claw feet (posterior tibial nerve damage). Two different classification systems for leprosy exist depending on available diagnostic facilities. In the field and in resource-limited limited settings, WHO has sug- gested clinical classification according to the number of skin lesions present (up to five lesions is classified as paucibacillary and more than six lesions as multibacil- lary leprosy).2
This system of classification places a great
deal of emphasis on anaesthetic skin patches which are characteristic of tuberculoid forms of leprosy but it risks missing lepromatous cases of leprosy. If facilities and resources permit and if there is available expertise, slit skin smears should be taken to detect mycobacteria ba- cilli and to assess the bacillary load or ‘bacterial index’
(BI). If slit skin smears are negative and there is clinical uncertainty of the diagnosis, skin histopathology can sometimes be diagnostically helpful. These tests enable the use of the Ridley–Jopling system of classification which is more robust and relies on the clinical and his- tological features together with the bacterial index.3 Classifying leprosy is important as it determines the
choice of multi-drug therapy (MDT) which was suc- cessfully implemented in 1982. Prior to MDT, dapsone monotherapy was given for decades but was found to be associated with increasing rates of relapse and the development of drug resistance. WHO’s current recom- mendations for MDT are combinations of monthly rifampicin (600mg) and daily clofazamine (50mg) and dapsone (100mg), which are given for a minimum of 6 and 12 months for paucibacillary and multibacillary leprosy respectively. Rifampicin is highly bactericidal and therefore patients are no longer deemed infectious after the first dose. The most significant change to MDT since its introduction was to the duration of therapy which was significantly shortened for multibacillary leprosy from 24 months or until the BI was negative to the current regimen of 12 months. The early longer MDT regimens proved to be highly effective and drug resistance or failure was not a significant issue. The current shorter regimens have been an issue of debate amongst leprologists as patients with multibacillary leprosy are at greater risk of relapse when the drugs are discontinued and if the mycobacteria are not completely eradicated.4 Even with bacteriological cure, treated patients still
have long-term risks of serious and debilitating compli- cations: sensory impairment can predispose to neu- ropathic ulcers and the risk of osteomyelitis; acquired motor impairment can cause muscle weakness and contractures; and trigeminal and facial nerve involve- ment can result in blindness. Therefore, even after completing MDT, leprosy patients need appropriate care and advice to prevent these potential complica- tions of established nerve damage.5
In addition, there is
the risk of ‘reactions’, which are serious immunologi- cal phenomena that manifest as acute inflammation of skin and nerve lesions. There are two types of reactions: type 1 or ‘reversal reactions’ which are a delayed-type hypersensitivity reaction directed against M leprae antigenic determinants; and type 2 or ‘erythema nodo- sum leprosum’ reactions which are probably immune
Figure 2 Nodule of lepromatous leprosy seen on the ear and enlarged greater auricular nerve.
July 2012
Figure 3 Ulnar nerve impairment with clawing of the lateral fingers and small muscle wasting.
Africa Health 53
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