Sunset syndrome

Introduction Sunset syndrome is a clinical manifestation of Vogt-Koyanagi-Harada syndrome. In the late course of the disease, choroidal pigment cells and retinal pigment epithelial cells are severely damaged and lost. The fundus is red when the sun sets, called sunset glow or evening. Still like the fundus. Every effort to avoid provoking the body's immune response is the key to preventing autoimmune diseases. To maintain physical fitness, increase the body's ability to resist disease, do not fatigue, excessive consumption, quit smoking and alcohol.

Cause

Cause:

(1) Causes of the disease

The etiology of Vogt-Koyanagi-Harada syndrome is not fully understood, mainly related to autoimmune response and infection factors.

(two) pathogenesis

The pathogenesis of this disease is still not very clear. It may be that cell immunity and humoral immunity work together to cause disease.

1. Cellular immunity causes tissue damage: this damage is mediated by lymphocytes. The experiment confirmed that the lymphocytes of patients with this disease were sensitized by melanocyte surface antigen, and the sensitized lymphocytes attacked melanin as a target cell. That is to say, melanocytes are both antigens of immune response and target cells that are damaged by attack by sensitized lymphocytes. Antibodies against various components of the pigmented membrane have been detected from patients, the most important of which are antibodies against melanocyte surface antigens. The antibody destroys melanocytes by an anti-dependent cell-mediated cytotoxic mechanism, indicating that it is autoimmune caused by humoral immunity.

According to Sugiura, the disease is a melanocyte-specific autoimmune disease. The antigen that induces this autoimmunity is located on the surface of melanocytes. In normal people, since the antibody immunosurveillance system functions, the immune-active cells do not undergo an immune attack on their own melanocytes, and this state is called immune tolerance. In the case of this disease, the immune tolerance to autologous melanocytes may be terminated by the following two factors: 1 primary surveillance of immune function; 2 changes in melanocytes, antigens on the cell surface Sex is modified.

2. The role of immunogenetics in pathogenesis: Many autoimmune diseases are known to be closely related to human leukocyte antigen (HLA). Sugiura Qingzhi detected HLA-A, B, and D locus antigens in a group of patients. The frequency of HLA-BW54 antigen was 45.2%, the control group was 13.2%, the LD-Wa antigen was 66.7%, and the control group was 16%. The relative risk of HLA-BW54 was 4.9, and that of LD-Wa was 10.5, that is, the incidence of carrying these two antigens was 4.9 times and 10.5 times that of non-carriers, respectively. HLA-BW54 and LD-Wa are HLA-B and D-site antigens, respectively. These two antigens are not found in whites, and thus are considered to be unique antigens in the Far East. The disease is more common in Japan and the East, but less common in European and American whites, which also shows that the disease is closely related to immune genetics. Ohno also confirmed that the relative risk of DR4 and MT3 in patients with this disease increased by 15.2 and 74.5 times, respectively, compared with the control. This disease, like other autoimmune diseases, is also closely related to HLA-D (DR) site antigen (MT3). All cases with D (DR) site antigen were positive for MT3, indicating that the disease is highly correlated with immunogenetic factors. DR4 and MT3 are also antigens unique to Japanese and Far East people. See the related effects of Vogt-Koyanagi-Harada syndrome and HLA.

3. Pathology: The typical pathological change of this disease is choroidal histology: the lesion is a nodular granuloma lesion formed by lymphocytes, plasma cells surrounded by epithelioid cells and multinucleated giant cells, and there is no necrotic lesion in the center. Epithelioid cells are large cells with clear cytoplasm and contain many organelles, lysosomes and phagosomes. Melanin particles are visible in the phagosome. There is a Delen-Fuchs nodule that protrudes inward into the choroid. This nodule is composed of degenerated retinal pigment epithelial cells and epithelioid cells. The pathological changes of the iris ciliary body are essentially the same as the choroidal changes. They are lesions composed of epithelioid cells, lymphocytes and plasma cells. Sometimes there are signs of mitosis of lymphocytes, but in the iris, epithelioid cells are inferior to the choroid. Visible inside. Corneal epithelial melanocytes and melanin particles are reduced, while Langhan cells are increased. Normal Langhan cells are only found in the superficial layer, and the disease can also be seen in the basal layer.

The pathological changes of the skin are the same as those of the corneal epithelium, that is, the melanocytes and melanin particles are reduced, and the Langhans cells are increased. This cell is also found in the basal layer. A small amount of lymphocytes and mild inflammatory cell infiltration were observed in the epidermis. There is no melanocytes in the dermis, but melanocytes derived from the mother's plaque can be seen in the hips of the Mongolian plaque, and there is a fusion of melanocytes with lymphocytes, which is completely seen in the pigmented membrane. the same. Infiltration of cells in the dermis is very light, no epithelial-like cells are formed, and occasionally lymphocytic infiltration is accompanied by epithelioid cells. In addition to Langhan cells, there are still identical cells in the dermis with rod-shaped granulosa cells, which have active migratory and phagocytic functions.

According to the observed characteristics of melanocytes, they can be divided into superficial and deep types. The melanocytes in the pigmented membrane, meninges, inner ear and dermis belong to the deep type, while the melanocytes in the corneal epithelium and epidermis belong to the superficial type. The characteristics of the two types of melanocytes are significantly different, that is, the deep melanocytes lose the function of synthesizing melanin. Under electron microscope, the cell wall of this type of cells is thin and the basement membrane is incomplete. On the contrary, superficial melanocytes have active melanin synthesis. The cell membrane has no deep basement membrane features.

an examination

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diagnosis:

VKH syndrome begins with an acute attack and the course of the disease is repeated. There are two clinical types, namely Vogt-small willow type (VK type) with exudative iridocyclitis and primary field type (H type) with exudative choroiditis. Both before the eye disease, fever, headache, dizziness, nausea, vomiting, strong, Kernig sign positive, cerebrospinal fluid pressure and other symptoms and signs; cerebrospinal fluid examination can often see increased lymphocyte and protein content; EEG There are also pathological changes in the examination. In these cases, type H is more common and severe than type VK.

1.VK type: At the beginning of the onset, the patient has complaints such as strong photophobia, tearing, eye pain, and sharp decline in vision. Eye examination showed significant ciliary congestion, grayish white and even sheep-like dense KP, strong positive Tydall phenomenon, iris edema, dilated pupils, post-iris adhesion, insensitive to atropine and quickly covered by gray-white exudate A series of signs of acute exudative iridocyclitis. The fundus condition is not known. If the patient complains of a flash, it suggests that the inflammation affects the choroid. The course of the disease is long and repeated, and each time it is repeated, the condition is aggravated once, and eventually blindness or eyeball atrophy is caused by secondary glaucoma and complicated cataract.

2. Type H: Both eyes have a disease at the same time or several days apart. Due to the first choroidal invasion, patients often complain of sharp decline in vision, flashing sensation and hyperopia. Although there is vitreous opacity, it is still satisfactory to see the fundus. The optic disc is congested, the state of the eye, the retinal vein filling and distortion. Retinal edema opacity was limited to the radial wrinkles around the optic disc and the macula at the beginning. As the inflammation increased, the choroid oozes a lot, making the entire retina pale gray and exudative retinal detachment. The detachment is often located on the underside of the fundus and is wavy or hemispherical. In the late course of the disease, choroidal pigment cells and retinal pigment epithelial cells are severely damaged and lost. The fundus is red when the sun sets, and it is called the sunset or the eve of the eye. This typical red tone can be uniform, or it can be mixed with pigmented spots and yellow-white cords or spots located beneath the retinal blood vessels.

Differential diagnosis

Retinal detachment: Retinal detachment is the separation of the neuroepithelial layer of the retina from the pigment epithelial layer. There is a potential gap between the two layers, and the liquid retained in the gap after separation is called subretinal fluid. According to the cause, it can be divided into rhegmatogenous, traction and exudative retinal detachment. The part of the retinal detachment does not work properly, and the brain accepts incomplete or total loss of images from the eye.

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