Acanthamoeba scleritis
Introduction
Introduction to Acanthamoeba scleritis Acanthamoeba scleritis is a scleritis caused by Acanthamoeba, which is a serious threat to vision and has a long course of disease and is a chronic progressive scleral lesion. basic knowledge Sickness ratio: 0.0001% Susceptible people: no special people Mode of infection: contact infection Complications: anterior uveitis
Cause
The cause of Acanthamoeba scleritis
(1) Causes of the disease
Acanthamoeba is a small amoeba that can be found in soil, polluted fresh water, sea water, swimming pools, grains and livestock. Acanthamoeba is also found in human nasal mucosa and can also be found in contact lenses or lens cleaning. Solution, in nature, Acanthamoeba exists in both trophozoites and cysts. The trophozoites are active forms of Acanthamoeba, which are mainly propagated in a mitotic manner. The cyst is the static of Acanthamoeba. The form can withstand the damage of dryness, high temperature and chemical substances. The two forms can be transformed into each other, and the transformation mechanism is not fully understood.
(two) pathogenesis
The spread of Acanthamoeba oblitera can cause Acanthamoeba scleritis, which can be directly infected by Acanthamoeba or caused by the immune response to the killed Acanthamoeba. Studies have shown that due to the sclera The normal structure and defense function are destroyed, the glycoprotein in the sclera tissue is exposed, it is easy to bind to the protein of Acanthamoeba, produce cytolysis factor, promote the destruction of scleral tissue, and the enzyme released by Acanthamoeba or inflammatory cells It can lead to necrosis and thinning of the sclera. Normal Acanthamoeba can activate the complement bypass pathway. The killed amoeba and its metabolites can cause an immune response, causing inflammation of the scleral microvessels, leading to immune-mediated Scleral inflammation, in recent years, there is an increase in the destructive tendency of Acanthamoeba scleritis, the patient is young, healthy, and immune function is normal, but at least one of the following risk factors:
1 history of mild corneal and/or scleral trauma;
2 direct exposure to soil and contaminated water;
3 wear contact lenses.
Prevention
Acanthamoeba scleritis prevention
Preventive work is especially important for people wearing contact lenses.
Complication
Complications of Acanthamoeba scleritis Complications, anterior uveitis
Anterior uveitis, but relatively rare.
Symptom
Acanthamoeba sclera symptoms common symptoms tears in the eyes have foreign body sensation nodules edema eye pain congestion keratitis high eye pressure photophobia
Acanthamoeba scleritis is mostly diffuse or nodular, can develop into necrotizing anterior scleritis and cause scleral staphyloma. At the beginning of the disease, there are red eyes, photophobia, tearing, foreign body sensation, conjunctival sac secretion, eye pain. With visual acuity decreased, more than 50% of patients have severe eye pain, intense nighttime, and radiate to the trigeminal nerve branch. The prognosis of diffuse anterior scleritis is relatively good, the sclera is diffusely congested, the conjunctival edema is easy, and the lesion is easy. Diffusion, the lesion range is limited to about 60%, nodular anterior scleritis can form deep red nodules, completely inactive, hard and tender, the nodules and the superficial scleral tissue on the boundary are clear, the surface of the blood vessels are The nodules are ruptured, and the necrotizing anterior scleritis is destructive. The first manifestation is localized sclerosing scleritis, which is accompanied by acute congestion. The plaque-like avascular zone of the sclera is caused by occlusive vasculitis in the outer layer of the sclera. This avascular zone of the lower sclera matrix edema, lesions can have different progress, some inflammation can be limited, in most cases, the scleral tissue in this area is almost completely necrotic, inflammatory lesions develop to the sides of the eyeball Loss and the entire front of the sclera, scleral necrosis parts, uveal exposed, if prolonged sustained high intraocular pressure, the formation of staphyloma.
Acanthamoeba scleritis is often accompanied by annular exudative stromal keratitis, which initially manifests as permanent or recurrent dendritic or punctate corneal epithelial damage, gradually developing into a matrix infiltration and radial infiltration along the corneal nerve. The corneal stroma forms an inflammatory infiltrating ring, and a white satellite is seen around the circumference. The central matrix resembles discoid keratitis, accompanied by anterior chamber empyema, occasionally with posterior elastic layer wrinkles, post-corneal KP and repeated corneal epithelial exfoliation. Acanthamoeba scleritis has a long course and progresses slowly. Most patients have severe eye pain and may be caused by the neurotropic of Acanthamoeba.
Examine
Examination of Acanthamoeba scleritis
Use biopsy specimens, contact lenses and contact lens cleaning solutions, preservation solutions, and place Escherichia coli such as Escherichia coli, Enterobacter aerogenes, Klebsiella pneumoniae at room temperature. In the nutrient-free agar medium prepared by the method, the growth of Acanthamoeba can be made positive only for 24 hours.
Confocal laser microscope
Amoeba trophozoites and cysts can be found.
2. Angle scleral biopsy
It can be carried out when necessary. Acanthamoeba can directly invade the scleral tissue, accompanied by infiltration of inflammatory cells mainly composed of polymorphonuclear leukocytes, a small amount of macrophages and lymphocytes, and biopsy tissue can also be stained with Giemsa, Masson. Amoeba can be found by triple staining (Masson trichrome), GMS, Wright staining, CFW and fluorescein labeled antibody staining.
Diagnosis
Diagnosis and identification of Acanthamoeba scleritis
Because Acanthamoeba scleritis is rare, often misdiagnosed, even if the first consideration of Sclerotioracicola infection, the diagnosis is still difficult to confirm, detailed history, slit lamp examination, special staining of smear or biopsy tissue and E. coli Cultured without nutrient medium, can be diagnosed early, conventional corneal epithelial smear can not find negative culture of Acanthamoeba or Acanthamoeba, because Acanthamoeba is only present in the corneal stroma.
Mainly differentiated from monosporous scleritis, eye pain and physical signs are inconsistent, antiviral therapy is ineffective, and tissue culture and biopsy have amyxoma protozoa for its diagnostic identification.
