This disease was at one time spread over the whole of Europe, but is now limited to certain localities in Norway, Russia, Iceland, and the coast of the Mediterranean. It is still somewhat prevalent in Asia, especially India, Japan, and China; in Africa, where it is very prevalent in Egypt, Abyssinia, and the Islands of the East Coast; and in America, especially in the West India Islands and Mexico. (See Hirsch, "Geograph. Path.," vol. ii., p. 1).
The disease is generally regarded as hereditary, but a considerable number of cases of contagion have been observed.
The question of contagion as a cause of leprosy has been till lately an undecided one. But recently several cases of communication to Europeans, evidently by contagion, have been published, one in which it was communicated by vaccination. A final demonstration of contagion has been furnished by the inoculation of a condemned criminal at Honolulu by Dr. Arning. The inoculation was successful, but the period of incubation was very prolonged. It is probable that the incubation may extend over several years, and if this be so, it will be frequently very difficult to trace the source of contagion. The reality of contagion has received its final demonstration in the case of Father Damien, a Catholic priest who ministered to a leper colony and contracted the disease, of which he died . in 1889. The researches of Thin seem to show that leprosy was introduced into Italy about the time of Christ, and that it spread thence into the countries of Northern and Western Europe. Within a few centuries it had spread to such an extent and excited such disgust and terror, that the populations were roused to drive the lepers from their midst. They were now gathered into ' lazar-houses,' and otherwise isolated. With the adoption of these measures leprosy began to disappear, and soon became almost extinct in the principal countries of Europe.
The Leprosy bacillus somewhat resembles the tubercle bacillus, and can be stained by similar methods. But it can also be stained by methods to which the tubercle bacillus does not react. Its cultivation is very difficult, but is said to have been accomplished on peptone glycerine serum. It is also stated to have been successfully inoculated in animals, and in man there is the successful case of inoculation referred to above. The bacillus is present in quite enormous numbers in the lesions in the skin in leprosy. It presents itself in the interior of round cells (the lepra cells of Virchow) which are considerably larger than leucocytes. (See Fig. 134.) These cells are to some extent the endothelium of the vessels, but other fixed connective-tissue cells apparently .act as phagocytes to the leprosy bacillus. The bacilli are so numerous as to suggest that the characteristic cutaneous swellings may be in part due to the actual bulk of the bacilli.
The disease occurs in two forms which are designated Lepra tuberculosa and Lepra anaesthetica. In the first the new-formation has its seat in the skin or mucous membrane; in the second it is the nerves which are affected. The tubercular form is sometimes called Elephantiasis graecorum.
In both forms the onset of the symptoms is characterized by general -constitutional disturbance in the form of malaise and frequently fever, along with an erythematous eruption of the skin. These symptoms are more pronounced in tubercular leprosy than in the anaesthetic form, which may be very insidious in its onset. Their occurrence would indicate that the infection is present in the blood, and would make the phenomenon of leprosy analogous to the second stage of syphilis. This analogy is further borne out by the symmetrical character of the lesions, which are described below. At the same time the bacillus has not been found in the blood, and its position and condition during the long period of incubation are quite obscure.
Fig. 134. - Leprosy bacillus. Those in groups are inside cells.
Fig. 135. - Leprosy. The face shows nodular swellings, especially on nose, eyebrows, lips, chin, and ears. Patient had also a large ulcer on right leg, and a small one on left. (Virchow).
Tubercular leprosy occurs mainly in the skin, but extends also to mucous membranes. After the acute symptoms referred to above, the erythema, which is a general eruption, passes off, and the permanent lesion limits itself, for the most part, to the exposed parts of the body. The skin of the face and hands are the parts most affected, and the legs if they are exposed. Of the mucous membranes, those of the mouth and larynx are often involved. The disease also extends to the lymphatic glands. In the skin there appear larger or smaller swellings, at first red or bluish in colour, which become firmer and harder. These tubercles may reach the size of a hazel nut or a walnut. They consist of granulation tissue in which cells of various sizes have replaced the cutis vera. These cells contain the bacilli. As in other granulation tumours, we often have ulceration, or, as in the case of lupus, there may be cicatrization without ulceration. By the formation of the swellings and cicatrization, great deformities frequently result, so that the patients have often a peculiarly hideous appearance, the face being knobbed and gnarled (Fig. 135).
Nerve leprosy is characterized by the stems of the peripheral nerves-becoming the seat of spindle-shaped swellings, sometimes of considerable length. The granulation tissue here is in the interstitial connective tissue, so that the nerve-fibres are separated and compressed. The new-formation sometimes, but rarely, extends to the membranes of the spinal cord or brain.
The nerve affection leads to neuralgias and to conditions of the skin which are related to the interruption of the conductivity of the nerves. Localized patches of anaesthesia occur. There are patches in which the colour varies, being darker or paler than normal. In the older patches, the central parts are mostly pale (white leprosy). Deep ulcerations sometimes follow, not infrequently leading to separation of the fingers or toes. No bacilli have been found in these peripheral lesions; they are simply the result of the interference with the nerves.
In leprosy there are sometimes tumours formed in internal organsr but this is very rare.
For a historical account see Hibsch, Handbook of hist, and geograph. path., Syd. Soc. transl., vol. ii.; see also Virchow, Geschwiilste, vol. ii.; Gull, Guy's Hosp. Rep., 1859; Carter, Med. Chir. trans., lvi., and Path, trans., xxvii.; Hansen, Virch. Arch., vol. lxxix.; Neisser, Ziemssen's Handb. d. spec. Path., vol. xiv., and Virch. Arch., vols, lxxxiv. and ciii.; also Neisser and Cornil et Suchard, in translated essays, New Syd. Soc, 1886. Contagion - Munro, Etiology and Hist, of leprosy; Besnier, Acad, de Med.-, Oct. 11, '87; Gairdner, Brit. Med. Jour., 1887, i. 1269, ii. 799, 1055, and 1119; Thin on Leprosy, a full account of history, pathology, etc., London, 1891; Arning's case, Brit. Med. Jour., 1888, ii., 1171; Bevan Rake, Various reports of Leper Hosp., Trinidad; Hutchinson, Archives of Surg., i.-iii.