Histopathological correlation of skin biopsies in leprosy

Introduction

Leprosy is a chronic, infectious disease caused by Mycobacterium leprae which expresses itself in different clinico-pathological forms, depending on the immune status of the host.[1]

The study of pathological changes in leprosy lesions has contributed a great deal to understanding of the disease and clinico-pathological correlative studies have provided further insights into the disease, its varied manifestations and complications. Pathological examination helps to confirm a presumptive clinical diagnosis and also helps for exact typing.[2],[3]

The study was undertaken to correlate different types of leprosy histopathologically and clinically.

Materials and Methods

A total of 372 leprosy skin biopsies were studied over a period of 24 months between 1997 and 1999. All the biopsies were received in the Department of Pathology, J.J.M.M.C, Davangere. Cases were selected regardless of their age, sex, socio-economic status and occupation. Biopsies were fixed in 10% formalin and processed. 5 micron sections were stained with haematoxylin and eosin; modified Fite and studied.

Results

There were 242 (65.05%) males and 130 (34.95%) females between 3 and 86 years of age. The majority of patients were in the age group of 20-29 years (20.70%) and least affected were children below 9 years (6.45%).The distribution of cases in the leprosy spectrum based on clinical and histopathological criteria are as shown in [Table - 1].

Although almost similar distribution of cases was seen in clinical and histopathological classification, number of IL cases were more by histopathological classification than by clinical classification.

The correlation between clinical and histo-pathological classification was as shown in [Table - 2].

Overall coincidence of diagnosis of classification was seen in 233 cases (62.63%). The correlation between the two modes of classification was maximum at lepromatous pole than at tuber-culoid pole, with the correlation being least in IL.

The coincidence of classification by two modes, histopathological and clinical examination as percentage for each mode of examination was as shown in [Table - 3]. While correlating the histopathological diagnosis with clinical diagnosis, maximum correlation (80%) was noted in LL patients followed by BL(70%), BT(66.54%), BB(50%), Tr (46.15%) and it was very poor in IL (20%).On the other hand, clinical diagnosis coincided with the histopathological diagnosis more often for BT (88.18%) type than for other types.

Discussion

In the present study, Ridley-Jopling classification was used to classify leprosy both clinically and histopathologically. Out of 372 cases, the diagnosis of 233 cases correlated clinically and histopathologically (62.63%).

The Ridley-Jopling classification is based on clinical, histopathological and immunological features, which is widely accepted by histopathologists and leprologists. The discordance between clinical and histopathological diagnosis was noticed because the clinical diagnosis was made on the lines of Ridley -Jopling classification, even when a histopathologial examination had not been done.[4]

[Table - 4] shows comparative study of clinico-pathological correlation by different workers in percentage. It is clear from [Table - 4] that, the correlation was better at lepromatous pole (LL and BL) than the tuberculoid pole (TT and BT). The correlation was least in IL except in the study conducted by Jerath and Desai in 1982.

There is no independent gold standard for diagnosis of leprosy. Taking any of the clinical signs, clinical types, histopathologicaI parameters or histopathological types as a gold standard is not ideal. The variation in different studies may be due to different criteria used to select the cases and difference in number of cases of each type. Various factors also influence the histopathological diagnosis such as differences in sample size,choosing the biopsy site,age of the lesion,immunological and treatment status of the patient at the time of biopsy.[4],[5]

IL is an early and transitory stage of leprosy found in persons, whose immunological status is yet to be determined and it may progress to one of the other determinate forms of the disease. The IL type appears to be problematic due to the non-specific histology of their lesion. The diagnosis of IL also depends on many factors such as nature and depth of the biopsy, the quality of sections and number of sections examined, both H& E stained and acid-fast stained.[4],[7],[8]

Clinical diagnosis of early leprosy lesions offer difficulties even to experienced dermatologists and leprologists. A definitive diagnosis may be possible by histopathological examination. The other important point to be considered is inter-observer variation, both clinically and histopathologically.[4],[9]

As there can be some degree of overlap between different types of leprosy, both clinically and histopathologically, correlation of clinical and histopathological features along with bacteriological index appears to be more useful for accurate typing of leprosy than considering any one of the single parameters alone.