Classification of leprosy.

The three latest International Congresses of leprologists (Madrid 1953, Tokio 1958, Rio 1963) have recognised two polar types of leprosy, tuberculoid and lepromatous and one inter­ mediate group, borderline. These three categories faintly reflect the con­ cept of a spectrum of clinicai, immunological, bacteriological and histological signs. Apart from these categories a group of cases with incharacteristic macular lesions, not fitting into the spectrum, called indeterminate, is recognised. Although the basic concept of this classifica­ tion is now almost generally accepted, few workers are really satisfied with its application in practice. Not a few workers have difficulties in fitting certain types of patients into this classification. Often there is agreement about the right place of patients in the spectrum, but disagreement about the designation. The result is that considerable differences in type distribution are reported from the same area by different workers. Reports are difficult to compare unless one is familiar with the views of the investigator about classification. The greatest differences are found in the pro­ portions of indeterminate and 'intermediate' patients. The less experienced worker is confused by designations such as reactional tuberculoid and tuberculoid in reaction, indeterminate and inter­ media te, dimorphous and borderline, which cover part of the same field but are not inter­ changeable. It can hardly be denied that the situation in the field of classification is still highly confusing for the average fieldworker in leprosy and rather indigestible for the general practioner who has to deal with leprosy only incidentally and who has no time nor need for a special study of the subject. Much can be said for a simple classification for the lay-worker and a more detailed classi­ cation for the scientific worker. It is however doubtful that a simple classification can be de­ signed without loss of significance. Classification should give information about important items such as infectiousness, complications to be expected, duration of treatment needed, ulti­ mate prognosis, etc. A division between open and closed cases has only momentary value. The open case of today may be a closed case tomorrow, and the reverse. A division between benign and malign is an unsatisfactory substitute for cases on lhe tuber­ culoid si de and on the lepromatous side. Many tuberculoid patients truly are benign, but many of the most severely crippled patients also belong to the tuberculoid category. Lepromatous leprosy, called malign, may be present for a decade or more, without serious complications and without producing deformity. The fact that leprosy patients present an un­ in terru pted scale of all degrees of tissue resistance to Myco !eprae means that each grouping is arbitrary and a compromise. One should not expect sharply defined groups. It is not logical to distinguish between tuber­ culoid and lepromatous types and borderline and indeterminate groups. In fact all categories are groups. At most one could speak of patients as tuberculoid and lepromatous polar types, e.g. the small, single, rapidly self healing typical tuberculoid lesion and the pure, primary, diffuse lepromatous case respectively. It is also not logical to divide the scale into a very large tuberculoid group, a very small bor­ derline group and a large lepromatous group. The large groups thus become very heterogellous, whereas the borderline group is restricted to a small, rather well defined section of a large inter­ mediate (dimorphous) group. Nor is it logical to classify together a large number of macular lesions with an entirely different evolution, but which cannot be fitted into the scale at first glance, into an indeterminate 'dustbin'.