Clinical Classification of Leprosy

Abstract

Leprosy is a chronic disease with varied manifestations. Its varied course, prognosis, and complications require a distinct classification. A uniform classification helps in communication at field level with appropriate diagnosis and management of disease. But at the research level, the perception is different. Here we have described currently available different classifications of leprosy to meet the expectations of both primary healthcare workers and researchers.

Introduction

Leprosy can present with cutaneous lesions and/or neural symptoms. The wide variations in disease presentation and its course, prognosis, and complications force one to consider these variants as a distinct entity and need to classify the disease. But a single classification can’t meet all the criteria at all levels. Hence, a uniform classification by WHO helps in easy communication among field workers and early diagnosis and treatment of leprosy. The comparison of clinical, histological, bacteriological, and immunological parameters by Ridley-Jopling helps the researchers to understand the finer aspects of the disease.

Classification of Leprosy

Classification of leprosy is important because it decides the line of treatment and stage and prognosis of the disease.

Criteria Deciding Classifications

• 1. Bacteriological criteria: measures the density of organism in lesions and estimated by slit skin smear technique or in biopsy specimens.

• 2. Immunological criteria: deficiency of cell-mediated immunity against M. leprae is measured by lepromin testing. Patients are classified as lepromin positive (good immunity) and lepromin negative (poor immunity).

• 3. Histological criteria: it reflects the actual process going on inside the body in the form of tissue reactions. It is the most definitive criteria for defining different entities.

• 4. Clinical criteria: Easiest to apply as clinical features can be identified and applied easily.

Types

Madrid classification, Indian, New IAL, Ridley-Jopling, WHO classification

Ridley-Jopling Classification [1, 2]

Defined five groups on the basis of clinical, bacteriological, histological, and immunological features (Table 1.1). It is very useful in research purposes, but not feasible in primary health centers and field levels. This classification does not include indeterminate type and pure neuritic type of leprosy.

• 1. Tuberculoid leprosy (TT)

• 2. Borderline tuberculoid (BT)

• 3. Borderline borderline (BB)

• 4. Borderline lepromatous (BL)

• 5. Lepromatous leprosy (LL)

Table 1.1 Characteristics of Ridley-Jopling classification [3]

Indian Classification [4]

It includes six groups that have maculo-anesthetic (MA) and pure neuritic as separate categories. The main drawback was the classification was not entirely clinical and its usefulness at all levels of leprosy workers was doubtful. But it adds the pure neuritic leprosy cases which were not in Ridley-Jopling classification.

The types are as follows:

• Lepromatous (L)

• Tuberculoid (T)

• Maculo-anesthetic (MA)

• Polyneuritic (P)

• Borderline (B)

• Indeterminate (I)

New IAL Classification [5]

A modification of Indian classification has been adopted by IAL where maculo-anesthetic (MA) leprosy was merged with tuberculoid (T) leprosy.

• Lepromatous (L)

• Tuberculoid (T)

• Polyneuritic (P)

• Borderline (B)

• Indeterminate (I)

WHO Classification (1988)

It was the most important classification of the disease for any treating leprologist. The patients were categorized depending upon whether slit skin smears demonstrate any bacilli or not.

Paucibacillary leprosy (PB): Only smear-negative cases and include indeterminate (I), tuberculoid (T), and borderline tuberculoid (BT) cases under Ridley-Jopling.

Multibacillary leprosy (MB): All smear-positive cases and mid-borderline (BB), borderline lepromatous (BL), and lepromatous (LL) types under Ridley-Jopling classification.

WHO Classification (1998) [6]

Application of slit skin smear universally to maintain their quality in control programs was the biggest challenge. Hence, in 1998, the WHO categorized PB and MB leprosy depending upon the number of skin lesions to overcome the operational problem of slit skin smear.

• Paucibacillary single lesion leprosy (SLPB)

• Paucibacillary leprosy (PB) (two to five skin lesions)

• Multibacillary leprosy (MB) (six or more skin lesions and all smear-positive cases)

Current WHO Classification

For field workers, the WHO has classified leprosy based on number of skin lesions for treatment purposes (Table 1.2). The sensitivity and specificity of this operational classification tested using slit skin smear and biopsy results as the gold standard were found to be 63% and 85%, respectively. 8th WHO expert excludes SLPB [7].

Table 1.2 WHO classification for field workers

Classification Under NLEP, India (2009) [8]

This classification is currently used in India for treatment purposes. It considers the number of nerve involvement along with skin lesion count while categorizing PB and MB leprosy (Table 1.3). The main advantage includes early diagnosis of pure neuritic leprosy that constitutes around 4–5 percent of all leprosy cases in our country.

Table 1.3 NLEP classification

Conclusion

Not a single classification can only meet the expectations at all levels of leprosy workers. Currently, the WHO classification, based on skin/nerve lesion count, is simple and practical to follow for treatment purposes worldwide. Ridley-Jopling classification remains the most useful one for academic and research purposes.