Clinical review

An update on the diagnosis and treatment of leprosy☆

Global situation^1,2

Over the years through expert committees and study groups, the WHO has assumed responsibility for recommending guidelines especially to underdeveloped countries for the management of leprosy. These guidelines take into consideration not only their efficacy, but also the cost and availability of the necessary personnel. Although it has become literally the authoritative resource, one must recognize that in some endemic areas such as Ethiopia, Brazil, and India, and in the non-endemic areas such

Diagnosis of leprosy^5,6

Leprosy is a slowly progressive infectious disease caused by Mycobacterial leprae and complicated by potential intermittent hypersensitivity reactions (the so-called lepra reactions). It is highly infective with low pathogenicity and virulence and has a long incubation period. The skin, superficial peripheral nerves, anterior chamber of the eyes, and testes, all cooler parts of the body are the most frequently affected organs. Its geographic distribution varied in the past, but presently it is

Classification of leprosy¹¹

In 1966, Ridley and Jopling created a classification of leprosy, based on the immunologic response of the host to M leprae, into a five-group system: TT (polar tuberculoid), BT (borderline tuberculoid), BB (borderline), BL (borderline lepromatous), and LL (polar lepromatous) (Table III).¹² In 1982, the WHO study group for chemotherapy for control programs recommended the classification of all patients be based on Ridley-Joplin classification and the estimated bacterial load in skin-slit smears.

Reactions^13,15

There are two main categories of reactions in leprosy: Type I¹⁴ reaction, which is called a reversal lepra reaction and is an example of Type IV cell mediated allergic hypersensitivity reaction (Coombs and Gell); and Type II lepra reaction,¹⁵ which is reported as erythema nodosum leprosum and is an example of Type III humoral hypersensitivity reaction (Coombs and Gell) (Table II). Among the precipitating factors are physical and mental stress, multiple drug therapy, vaccines, pregnancy,

Hansen's disease and pregnancy^20,21

It is not uncommon for leprosy to present itself during pregnancy or early puerperium. Because of alterations in immune responses during pregnancy, leprosy patients who become pregnant are more prone to develop type I and II reactions, a downgrading of their disease, and relapses. Type II reaction usually occurs during pregnancy, especially during the third trimester and lactation. Type I reaction occurs, especially during puerperium. Infants run a relatively high risk of contracting leprosy

Hansen's disease and HIV disease^22,23

Unlike in tuberculosis, HIV disease has not had a significant impact on the clinical course of treated and untreated leprosy. However, it has been reported that the neuritis in co-infected people can be more severe and the reversal reaction may be more frequent after therapy. In endemic areas of HIV disease and leprosy, there does not appear to be a greater incidence of leprosy among HIV patients. It may be because of the very slow proliferation of the bacilli or the prolonged incubation

Therapy of nonreactive disease^24-26

In 1981, the WHO Study Group recommended multiple drug therapy (MDT) for the following reasons:²⁴

• 1.

  To address dapsone resistance and to discourage resistance to other drugs to be used.

• 2.

  To promote compliance and to get away from long-term monotherapy such as dapsone.

• 3.

  To keep rifampin in all therapeutic regimens because of its powerful bactericidal action and its effectiveness even when taken once a month.

• 4.

  To promote compliance and cost effectiveness.

In 1997, the WHO Expert Committee suggested that it

Vaccination

Anti-leprosy vaccination can be immunoprophylactic or immunotherapeutic.28., 29., 30. The immunoprophylactic aim is to restore the host recognition of shared mycobacterial antigens to promote TH1 responses to them, to induce CD8 cytotoxic cells, and to downregulate the proportion of T cells producing interleukins 4 and 5. The aim of immunotherapy is to switch off the mechanisms leading to immunopathology and to increase intracellular mechanisms by which bacilli are killed. The first vaccine

Treatment reactions

Unfortunately in spite of the significant advances in the chemotherapy of the disease in the last ten years, the understanding of the etiology and management of reactions has not changed much. MDT has not significantly impacted on the incidence of the reversal reaction (Type I). The treatment of the reaction14., 16., 31. depends on its severity, the type of the reaction, the presence of neuritis, facial involvement in Type I reaction, pregnancy, and drug allergies or adverse drug reactions. If

Prevention of disabilities and rehabilitation^36,37

The socioeconomic impact resulting from the physical and psychological disabilities of leprosy continues to be a burden in endemic countries. 25% of leprosy patients have some degree of disability, which are greatest in patients with BL and LL disease. It is greater in the older age group and males. Duration of disease and disability are directly proportional to each other. Hands are most frequently involved followed by the feet and eyes. There is an estimated 3 million people with physical

Conclusions

In spite of its relative simplicity, the classification of leprosy into paucibacillary and multibacillary disease based on lesion count in conjunction with an MDT program has proven to be effective in the reduction of the prevalence without significant relapse or Type I and II reactions. In fact, the incidence and severity of these reactions, especially Type II, have been reduced. When facilities are available to do the necessary laboratory studies, it is advisable to continue to use the

Acknowledgements

I acknowledge the exemplary technical support of Janet Couturier and the library assistance of Carol Spencer.