Mechanism of blister formation in leprosy patients

1- Leprosy patients frequently get burns of their anesthetic hands, because the lack of sensation prevents tham from realizing when the heat to which they are exposed is excessive and harmful. Hence they get burned unknowingly. 2- There are instances, however, in which the heat is not excessive for normal skin, but a part of one hand or one or more of the fingers are anesthetic. In that event blisters will appear only on the anesthetic parts, and not on the adjacent or on the corresponding normal parts. In these cases, evidently, the heat is not unbearable, or so great as to cause burns of normal parts. 3- To finf out why the effect of the same temperature should be so different in the anesthetic and in the nonanesthetic parts, an investigation was carried out on 22 patients during the last four years with the use of a thermocouple and light-trace galvanometer. The temperatures of the anesthetic and of the corresponding normal parts were recorded, before the application of heat (52°C for 5 minutes) and also immediately afterward. 4- Before the application of heat the anesthetic parts usually showed a lower temperature than the corresponding normal parts. This is held to be indicative of less active blood circulation in the anesthetic parts, due to contraction of the blood vessels. 5- After the application of heat the anesthetic parts always showed a higher temperature than the normal parts, indicative of less dissipation of heat. This is ascribed to insufficient dilatation of the blood vessels causing more accumulation of heat in the anesthetic parts than in the corresponding normal parts. 6- It is concluded that there are two factors in selective blistering. (a) The initial temperature of an anesthetic part being lower than that of the corresponding normal part, that part has to adjust to a greater difference of temperature after application of heat. (b) There is more accumulation of heat and more rise of temperature in an anesthetic part than in the corresponding normal part. These two factors appear to be responsible for the production of blisters in the anesthetic parts. A temperature which is just insufficient to produce blisters in a normal part may be just sufficient to roduce blisters in an anesthetic part. 7- The experiment reported further confirms my previous observation that the neural signs in leprosy are closely associated with capillary contraction, causing diminution of blood supply in the skin of anesthetic parts...

The mechanism of the neural signs and symptoms of leprosy

1- The signs and symptoms in leprosy such as hypopigmenation, anidrosis, keratosis, depilation, loss of sensation, paralysis, and trophic ulceration are often explained as due to degeneration of nerves, semsory, motor and sympathetic. 2- While recognizing that nerves are involved in leprosy, and that this involvement gives rise to various symptoms, the autor does not agree that degeneration of the nerves is always the cause of the conditions mentioned. The reasons for this belief are enumerated. 3- The clinical, therapeutic, and experimental work done to investigative this problem is described. 4- The results of the investigation indicate that the various signs and symptoms under discussion are due mainly to diminution of the blood circulation in the cappilaries of the skin, its appendages, the nerves, and the muscles affected by the disease. 5- It is concluded that, although these symptoms of lerposy are beyond doubt related to changes in the nerves, in a majority of cases the changes are not of the nature of degeneration of the nerve fibers. In most cases it is diminution of blood supply to the nerves that results in their dysfunction, and with the restoration of normal blood supply the function can be restored. Restoration of function is complete in some cases, but in other cases there may be actual degeneration of nerves or irreparable damage of the skin and other structures supplied by the nerve, and as a result the normal function cannot be restored or can be restored only partially. 6- The symptoms like hypopigmentation, anidrosis, keratosis, and depilation in patches probably do not depend on nerve involvement but are caused by diminished blood supply to the skin and its various appendages, and the disappearance of these symptoms and return of normal functions of the skin depend on the return of normal blood circulation to different parts of the skin.