Granulomatous changes in unilateral fundus

Introduction The most common change in ocular toxoplasmosis is granulomatous changes in the unilateral fundus. Ocular toxocariasis is an infectious disease caused by larvae of canine aphids or cat mites invading the tissues of the eye. Human infections are caused by food contaminated with the eggs of the mites.

Cause

(1) Causes of the disease

Canine aphids complete their life cycle in dogs. People and many other animals are infected with the second stage larvae, that is, the larvae hatch in the small intestine, and the blood flow through the intestinal wall is the second stage. Infections generally migrate from the blood vessels to the surrounding tissues in the dog, and the larvae become cysts. When the bitch is pregnant, the cyst or the larvae in the latent body move up again, and then enter the bloodstream and infect the puppies through the placenta before birth. After the second stage, the larvae enter the lungs and become the third stage larvae. They cough up and swallow them into the small intestine of the small dogs to form the fourth stage larvae. The larva matures within 3 weeks and begins to lay large numbers of eggs. One aphid can lay 200,000 eggs in one day. These infected eggs are discharged from the feces and polluted everywhere, becoming the root cause of human and animal infection. Dogs and cats are fixed hosts of Toxoplasma gondii, and humans are intermediate or accidental hosts that cannot mature or multiply in the human body.

Human infections are foods that are contaminated by fertilized eggs from infected dogs, especially those who are in close contact with dogs and cats and who do not pay attention to hygiene. The fertilized egg hatches in the small intestine, and the second stage larva enters the bloodstream from the intestine and is transferred to the liver, heart, lung, brain, eye and surrounding circulation. When the larva reaches a small artery whose vascular diameter is smaller than its body, it passes through the wall of the tube into its organ. In the human body, the development of Toxoplasma gondii does not exceed the second stage, so it is impossible to breed eggs in the human body, so the human stool test is negative. The larvae remain as silent in the surrounding tissue and are asymptomatic, but acute visceral aphid migration (VLM) occurs when they migrate. A single larva in the eye can cause vision loss. The larvae can enter the eye directly through the choroidal ciliary body or the central retinal artery. Before entering the eye, the larva can be a cyst and located in the surrounding tissue.

(two) pathogenesis

Canine nematodes are common intestinal parasites in dogs. The fertilized eggs of C. elegans are excreted in the feces and develop into infectious eggs under appropriate conditions. When swallowed by adult dogs, the larvae hatch in the small intestine and enter the bloodstream through the intestinal wall. The larvae cannot complete the migration from the lungs to the small intestine, so they cannot develop into adult worms, and only migrate to various tissues and organs in the body to form cysts. When the bitch is pregnant, the wrapped larvae can resume their habit of migration, and the blood enters the fetal body through the placenta and reaches the liver. After the birth of the fetus, the larva migrates to the lungs and reaches the pharynx with the trachea through the trachea. After swallowing into the stomach, it enters the small intestine and develops into an adult. Another infection method is that puppies within 3 months of age swallow infective eggs, hatch into larvae in the small intestine, larvae enter the intestinal lymphatic system, reach the liver through blood circulation, and then reach the pharynx through the lungs and trachea. After being swallowed, it develops into an adult in the small intestine. If a person ingests an infectious egg, the larva hatches in the small intestine and enters the intestinal wall through the lymphatic system to the mesenteric lymph node, then reaches the liver via the blood, and then goes to the lung with the blood. Since humans are not a suitable host for them, larvae cannot complete the migration from the lungs to the small intestine to develop into adults, so there is no egg in the human feces. The larvae spread throughout the body to form visceral larval migration, which can invade tissues such as liver, lung, brain, kidney, heart, muscle and eye. It is usually surrounded by reactive inflammatory granuloma, and many larvae can survive in the cyst for many years.

This disease can cause uveitis by directly invading the tissues of the eye and/or by causing an immune response. Larvae that invade the tissues of the eye often cause chronic vitreitis, focal necrotizing granulomatous inflammation, and are characterized by infiltration of eosinophils, epithelial cells, multinucleated giant cells, plasma cells, and lymphocytes around the larvae. Studies have found that patients with vitreous and aphid antibodies (IgG, IgE) in the vitreous and aqueous humor suggest that the immune response may play an important role in the occurrence of ocular toxoplasmosis.

an examination

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Whole body performance

Because the larva not only invades the tissues in the eye, it can also invade any other organs and tissues at the same time, causing fever, fatigue, weight loss, cough, wheezing, liver enlargement, itching of the trunk and lower extremities, rash and nodules. Individual patients may have manifestations of central nervous system involvement, such as encephalitis, brain eosinophilic granuloma, epilepsy, etc., but many patients do not have any systemic symptoms and signs.

2. Eye performance

Ocular symptoms may include dark shadows, decreased vision, etc., and the degree of visual acuity may vary greatly from patient to patient. Some patients are often difficult to express exact clinical symptoms due to their young age.

The most common change in this disease is a granulomatous change in the unilateral fundus, which is caused by the formation of cysts after invasion of the choroid by stage II larvae. Granuloma can occur in the posterior pole or in the peripheral part. The posterior pole lesions are 3/4 to 3 optic disc diameters, with gray or white bulging, often accompanied by mild to severe vitreous inflammatory response and decreased vision. Some patients may have chalk or strabismus. Granuloma in the peripheral part is a common change, often manifested as a white bulging lesion in the peripheral fundus, prone to retinal folds. Such wrinkles can extend from the peripheral portion to the optic disc, and the peripheral lesion sometimes changes like a snowy embankment of the middle uveitis.

Ocular arch tsutsugamushi can cause chronic endophthalmitis, manifested as mild anterior uveitis, post-irisal adhesion, ciliary membrane formation, vitreous inflammation and retinal detachment, occasionally causing anterior chamber empyema, optic discitis, macular edema Some patients may also have peripheral retinitis, which may be caused by larval arrest in the peripheral retinal vessels. In a few patients, live larvae can still be seen in the retinal vessels, and ocular tsutsugamushi can cause neuroretinitis. Retinal branch artery occlusion, scleritis, keratitis, etc. In addition, there is a report that the mites invade the lens and cause a lens mass.

Patients usually have a history of raising dogs or raising cats. Some patients have heterosexual convulsions. Systemic performance has a suggestive effect on diagnosis. Typical clinical manifestations of the eye are of great value for diagnosis. Laboratory tests are important for diagnosis. However, the diagnosis of toxoplasmosis is generally difficult, because the serum test of Toxoplasma gondii cross-reacts with other ascariasis, the stool test is negative, and some patients have no history of contact with cats and dogs, and can only be diagnosed according to the following points. :

1. Clinical manifestations: There are mainly eosinophilia, especially the limited granulomatous inflammation of the fundus, and the vitreous is generally turbid.

2. Serum ELISA method: It has high specificity for toxoplasmosis and no obvious cross-reaction with other helminth infections. It is more sensitive with vitreous examination. The disadvantage is that it is not easy for small labs to conduct such tests.

3. Aqueous and vitreous absorption: check eosinophils.

4. Ultrasound examination: granulomatous lesions can be found, which is more favorable for those who cannot see the fundus.

Differential diagnosis

Differential diagnosis of granulomatous changes in the unilateral fundus:

It should be differentiated from retinoblastoma, infectious endophthalmitis, intermediate uveitis, ocular toxoplasmosis, retinopathy of prematurity, permanent primordial vitreous hyperplasia, Coats disease, etc.

1. retinoblastoma: ocular toxoplasmosis can cause changes similar to retinoblastoma, especially both of which are prone to occur in children, can cause white sputum, but the consequences of the two are very different. Retinoblastoma is extremely harmful and can even cause death in patients, so retinoblastoma should be excluded in the diagnosis of ocular toxoplasmosis. Eye tsutsugamushi disease occurs in children 4 to 8 years old, the mass usually does not increase, often accompanied by significant inflammatory changes and proliferative vitreous changes, and retinoblastoma is more common in children 22 to 24 months, few of the above two Changes, and progressive enlargement of the mass, serum and aqueous humor-specific antibody assays, intravitreal cytology, retinal biopsy, etc. are of great value for diagnosis and differential diagnosis.

2. Infectious endophthalmitis: Infective endophthalmitis has a history of trauma, history of internal eye surgery, long-term application of immunosuppressive drugs, diabetes and other medical history. Patients have obvious red eyes, eye pain, photophobia, tearing, decreased vision and other symptoms, mostly conjunctival edema, corneal edema, massive anterior chamber fibrinous exudation or anterior chamber empyema, vitreous yellow-white opacity, white fundus or The lesions with unclear yellow-white borders progressed rapidly. Blood, urine and intraocular fluid bacterial culture, smear examination, etc. are helpful for diagnosis and differential diagnosis.

3. Intermediate uveitis: Central uveitis is typically characterized by vitreous lesions in the vitreous base and ciliary body flat and snowball opacity in the vitreous, often accompanied by peripheral retinal vasculitis, cystoid macular edema, and anterior chamber The inflammatory reaction is prone to complications such as opacity of the posterior capsule and retinal neovascularization. Although eye tsutsugamushi can have snow-like changes, its age of onset is small, and serum and aqueous humor antibodies are helpful for diagnosis and differential diagnosis.

4. Ocular toxoplasmosis: Toxoplasmosis is also prone to occur in children, and there is a history of raising dogs and/or cats, but the characteristic changes caused by them are around the retinal choroidal lesions in the posterior pole of the fundus. Active lesions, in addition to causing neuroretinitis, intermediate uveitis. Ocular arch tsutsugamushi mainly causes white uplift lesions in the posterior or peripheral part, prone to proliferative vitreoretinopathy and traction retinal detachment, and serum and intraocular fluid antibody detection may help differential diagnosis.

5. Retinopathy of prematurity: This lesion occurs in premature and low-weight children, involving both eyes, typically showing proliferative lesions, generally without signs of inflammation. In addition to causing changes in vitreoretinal proliferation, ocular toxoplasmosis mainly causes inflammatory changes, and has white-induced retinopathy. Specific antibody determination contributes to the diagnosis and differential diagnosis of both.

6. Coats disease: This disease mainly occurs in young males, characterized by the appearance of posterior subretinal white fibrotic lesions with telangiectasia and lipid exudation, but does not cause the anterior membrane of the retina. According to these features, it can be distinguished from ocular tsutsugamushi disease.

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