After the leprosy bacillus invades the organism, it is generally believed that the incubation period averages 2 to 5 years, ranging from a few months in the shortest cases to more than 10 years in the longest. If the disease develops, it is mostly unrecognized. Before the onset of typical symptoms, some of them tend to be characterized by general malaise, muscle and joint aches and pains, abnormal sensations in the extremities, and other generalized prodromal symptoms. These manifestations are not specific. Those who are more immunocompetent move towards the tuberculoid leprosy end of the spectrum, and those who are immunocompromised or deficient move towards the neoplastic end. The characteristics of the symptoms of each type of leprosy are described according to a five-level classification as follows:

I. Tuberculosis-like leprosy

In this type, the patient's immunity is strong, and Mycobacterium leprae is confined to the skin and nerves. Skin damage has patchy rash and plaque, the number is often one or two, the edge is neat, clear, often have obvious feeling (wet, pain, touch) obstacles distribution asymmetry, damage at the cui hair off, which is very important features. Prevalent in the limbs, face, shoulders and arms and other parts of the body susceptible to friction. The color of the plaque is light and reddish, and the surface is often without scales. The plaques are often dark red in color, well defined, with elevated margins either tilting inward and migrating to flattened atrophic centers, or tending to be semi-circular, circular, or bowed with varying thicknesses of the margins. The surface is mostly dry and scaly, sometimes the damage is seen as an accumulation of numerous small papules. Thick cutaneous nerves may be palpated in the vicinity of the damage. Sometimes the lymph nodes near the damage are also enlarged. Eyebrows usually do not fall off.

After the involvement of peripheral nerves in this type (such as the great auricular nerve, ulnar nerve, peroneal nerve, etc.), the nerve rods become enlarged in the form of pikes, nodules, or beads, and are hard and painful to the touch, mostly unilateral, and in severe cases, pustules or fistulas can be formed due to delayed-type hypersensitivity reactions. Some patients have neurological symptoms without skin damage, which is called pure neuritis. Clinical manifestations of nerve enlargement, corresponding parts of the skin sensory impairment and muscle weakness. When nerve involvement is severe, nerve nutrition, movement and other functional disorders occur, then the size of the interosseous muscle and interosseous muscle atrophy, the formation of "claw hand" (ulnar nerve involvement), "ape hand" (median nerve involvement), "hanging wrist" (radial nerve involvement). "(involvement of the radial nerve), "ulceration", "rabbit's eye" (involvement of the facial nerve), "resorption of the bones of the fingers (toes)" and many other manifestations. The deformity occurs relatively early.

Bacterial tests are generally negative in this type. The lepromin test is strongly positive. Bacterial immune function is normal or near normal. The histopathological changes of tuberculosis-like granuloma, which is characterized by the invisibility of "no infiltration zone" in the subepidermis, antacid staining can not be detected antacid bacilli. A small number of patients can heal spontaneously without treatment, or subside more quickly if treated. The general prognosis is good, but the formation of deformity is often not easy to recover.

Second, the boundary class partial tuberculosis-like leprosy

The occurrence of this type is similar to tuberculosis-like type, for the patchy rash and plaques, the color of light red, purple or brownish-yellow, the boundary is neat and clear, and some plaques appear in the center of the "blank area" or "hole-perforated area" (also known as non-infiltrating area). Some plaques have a "blank zone" or "punch hole zone" in the center of the plaque (also known as the no-infiltration zone or immune zone), forming a ring-shaped damage with clear inner and outer edges, and the skin within the hole zone seems normal. The surface of the damage is mostly smooth, with a few scales attached. The number of damages is multiple, varying in size, some scattered, with the trunk, limbs, face as the most common, more widely distributed, but asymmetric. Sensory deficits are present but are milder and slightly later than TT. The frown is usually not detached. Nerve involvement is thick and asymmetric, not as thick and irregular as TT. Mucous membranes, lymph nodes, testes, eyes, and viscera are less frequently and mildly involved.

Bacterial detection in this type is generally positive, with a cell density index (logarithmic classification, later the same) of 1 to 3+. The leprosin test is weakly positive, suspicious or negative. Cellular immune function tests are lower than normal. Histopathologic changes were similar to those of TT, but there were fewer and looser lymphocytes surrounding the epithelioid cells. A narrow "no-infiltration zone" is seen under the epidermis, and sections stained with antacid are free of or have a few Mycobacterium leprae. Prophylaxis is generally good. The "upgraded reaction" can become TT, and the "downgraded reaction" can become BB. Leprosy reaction is prone to deformity and disability.

Third, the intermediate boundary class leprosy

This type of skin lesions are characterized by polymorphism and multicolor. The rash type is macular, plaque, infiltration, etc.. The colors are wine-colored, withered yellow, brownish yellow, red, tan and so on. Sometimes two colors are present on one lesion. The edges are partly clear and partly unclear. The shape of the damage is banded, serpentine or irregular, and if it is striped and flaky, it is clear on one side and indistinctly infiltrated on the other. If it is a plaque, there is a "hole in the center", and its inner ring is clear and elevated, gradually slanting outward, and the outer edge is infiltrated and unclear, presenting an inverted saucer-like appearance. Some of the damage was red and white ring or multi-ring, shaped like a target or badge, known as "target-shaped spot" "badge-like spot". Some patients have bat-like facial lesions with spreading wings and grayish-brown color, which is called "bat-like face". It is common to see tumor-like and tuberculosis-like lesions on different parts of a patient's skin. Sometimes "satellite-like" lesions are seen. In some patients, thick cushion-like patches of nodules can be seen on the elbows, extensor surfaces of the knees, and hips. The surface of the lesions is slippery and soft to touch. The number of damages is large, varying in size, widely distributed and asymmetric. Nerve damage is followed by mild numbness, which is lighter than the nodule-like type and heavier than the tumor type. The eyelashes often do not fall off. Mucous membranes, lymph nodes, eyes, testes and internal organs can be involved.

This type is positive for bacterial detection, with a bacterial density index of 2 to 4+. The lepromin test reaction is negative. The cellular immune function test is between the two polar types. Histopathological changes of histiocytic granuloma, most of the subepidermal "no infiltration zone" exists, the histiocytes can be seen to varying degrees of differentiation to the epithelioid cells, generally small, some sections can be seen in the typical, atypical foam cells. Lymphocytes were few and scattered. Sections stained with anti-Hongo stain have more Mycobacterium leprae, and the prognosis is intermediate between the two polar types. This type is the most unstable, with an "escalating reaction" toward BT and a "de-escalating reaction" toward BL.

Fourth, the boundary class partial tumor type leprosy

The skin damage of this type has macular rash, papules, nodules, plaques and diffuse infiltration. Most of the damages seem to be tumor type damages, with more number, smaller form, unclear boundary, shiny surface and red or orange-red color. The distribution is wider and has a tendency to be symmetrical. Sensory disturbances within the damage are mild and appear late. Some of the damage is large, the center is a "hole in the zone", the inner edge is clear, the external infiltration is blurred. Eyebrows, eyelashes and hair can be lost, often asymmetrically. In the late stage, the deep diffuse infiltration of the face can also form a "lion face". In the middle and late stages, the mucous membranes are congested, infiltrated, swollen, and the lymph nodes and testes are enlarged and tender. Nerve involvement tends to be bilateral, more uniform and consistent, softer to the touch, the deformity appears later.

This type is strongly positive for bacterial detection, with a bacterial density index of 4 to 5+. Leprosin reaction is negative and cellular immune function tests show a defect. Histopathologic changes, the nature of the granuloma tends to foam cell granuloma, some histiocytes develop atypical epithelioid cells and some develop foam cells. Lymphocytes, often focally, are present between the foam cell infiltrates and characterize the pathology of this type. Sections stained with antacid have a high number of Mycobacterium leprae. The prognosis is better than LL and worse than TT, but still unstable, "escalating reaction" can become BB, and "downgrading reaction" can become LL.

V. Tumor-type leprosy

The patients of this type lack immunity to Mycobacterium leprae, which spreads all over the body via lymph and blood. Lymphatic and blood dissemination throughout the body. Therefore, the scope of invasion of tissues and organs is relatively wide. The skin damage is characterized by a large number, widely distributed and symmetrical, with blurred edges, tendency to merge, and greasy and smooth surface. The color of the skin, except for light spots, mostly develops from red to reddish-yellow and brownish-yellow. Sensory disturbances are mild. In the earlier stage, there was the manifestation of thinning of eyebrow and eyelashes, which began to fall off from the outer side of the eyebrow first, and later the eyelashes were also thinned out, which was a clinical feature of verrucous leprosy. The test for Mycobacterium leprae was strongly positive, and the skin damage included patchy rash, infiltration, nodules and diffuse damage. Early mottled damage is distributed all over the body, with the face, chest and back being the most common, the color is light red or light, the border is not clear, and it must be examined carefully under good light to be recognized. Slightly later, in addition to the continued increase in macular lesions, successive formation of shallow in, diffuse moist and nodular. In the face, due to the diffuse thickening of the infiltrate, the appearance of mild swelling, the eyelashes are often detached. Slightly later, the spot lesions merge into a large infiltration, or nodules appear on the spot lesions and diffuse infiltration, diffuse infiltration to the deeper part of the development, more obvious and serious. Often throughout the body. In the face, diffuse thickening, deepening of skin lines, hypertrophy of the nose and lips, earlobes become larger, eyebrows and eyelashes, hair thinning or large pieces of hair loss, nodules and deep in the infiltration mixed together, conjunctiva congestion, forming a "lion face" like appearance. There are numerous nodules of varying sizes on the extensor sides of the limbs, shoulders, back, buttocks, and scrotum. Later, due to partial absorption of the diffuse damage, there is marked sensory impairment and closed sweating. In the calves, the skin is mildly hardened, smooth and shiny, with ichthyosiform or serpentine-like damage, which does not recede for a long time, and in some cases, the hair is almost lost, and the visible remnants of the hair are mostly distributed along the vascular survival.

Although the nerve trunk is involved, the sensory impairment is mild and manifests later. The nerve trunk is mildly coarse, symmetrical and soft, and muscle atrophy, deformity and disability can be seen in the late stage.

Damage to the nasal mucosa appears early, first congested and swollen, and later with the aggravation of the disease, nodules, infiltration and ulceration occur. In severe cases, there can be perforation of the nasal septum, and when the bridge of the nose collapses, saddle nose is seen. Lymph nodes are involved at an early stage, mildly enlarged and often unnoticed, and in the middle to late stages they are enlarged significantly and tender.

The testicles are involved, first enlarged and then atrophied with tenderness, appearing *enlarged, etc.

Involvement of the eyes, conjunctivitis, keratitis, iridocyclitis, etc....... Visceral tissues and organs are also involved at the same time, such as hepatomegaly and splenomegaly.

This type of bacterial detection strong positive, 4 to 6 +. The leprosin test is negative. Cellular immune function test showed obvious defects. Histopathologic changes are characterized by foam cell granuloma structure, mainly composed of typical foam cells with abundant cytoplasm. There was a "no infiltration zone" under the epidermis. Sections stained with antacid have large numbers of Mycobacterium leprae, which may form bundles or balls. With early treatment, the prognosis is good, with fewer deformities, while late treatment can be crippling. This type is relatively stable, and only a very small number can be transformed to BL under certain conditions.

VI. Undetermined type of leprosy

This type of leprosy for the early manifestations of leprosy, is the primary, not included in the classification of the five levels, the nature of the unstable, can be self-absorbed or to other types of change. What type of leprosy it evolves into may depend on the strength of the patient's immune system, and it may change to other types, mostly to the tuberculosis-like type, and a few to the boundary type and tumor type. Clinical symptoms are mild and do not involve internal organs. Skin lesions simple, on the light red spots or light-colored spots, surface flat without infiltration, not atrophy. Cuiui hair can fall off. The skin lesions are garden, ellipsoid or irregular shape. The edge is clear or partially unclear, the distribution is not symmetrical, the lesions may have mild sensory impairment. Nerve stem involvement is relatively light, although there is an increase but the hardness is low, resulting in fewer movement disorders and deformities. Bacterial examination is mostly negative. The leprosin test is mostly positive. Cellular immune function tests are either normal or near normal, or markedly defective. Histopathologic changes are nonspecific inflammatory cell infiltration. The prognosis depends on the degree of cellular immunity developed in the organism. Those with a positive lepromin test and a normal cellular immune function test have a good prognosis. Some of its development can be self-healing, some evolve to other types.

Diagnosis:

The diagnosis of leprosy must be made carefully and patiently, with the aim of confirming the diagnosis at an early stage, without omission or misdiagnosis. Early treatment and early cure can prevent the disease from worsening, causing deformities and disability, or expanding the contagion. Diagnosis is mainly based on medical history, clinical symptoms, bacterial examination and histopathology and other examination results, comprehensive analysis and conclusions. For individual cases that are difficult to diagnose at the moment, regular follow-ups and follow-ups can be conducted, or the relevant departments can be consulted to exclude or confirm the diagnosis.

I. History questioning must focus on items related to leprosy, such as whether they are from endemic areas, family, relatives, friends and neighbors have the same patients, and whether there is a history of contact.

Second, the physical examination should be systematic and comprehensive, checking the skin, nerves and lymph nodes of the whole body under natural light.

When checking the nerves, it is important to pay attention to both the changes in the peripheral nerve trunks and the changes in sensory and motor functions.