Case 3 : A Case of Ocular Toxoplasmosis - PowerPoint PPT Presentation

Case 3 : A Case of Ocular Toxoplasmosis

Dr Johnson Tan

Medical Officer

Tan Tock Seng Hospital

c/o:

RE floaters x 5 days

No trauma

O/E :

VA 6/7.5 OU

No RAPD

Colour 15/15 OU

Decreased red desaturation RE

Confrontational fields full

Anterior segment NAD

RTL cells 1 +

• Rt superior optic disc swelling superiorly
• Superior-temporal peripapillary white lesion with indistinct edges
• Adjacent vasculitis
• What would be the next step?
• Take a full history

• No headache / neck stiffness / tinnitus
• No joint pains
• No mouth ulcers
• No dysuria
• No travel history
• No chronic cough / fever / constitutional symptoms
• No contact history with TB

• ESR / CRP
• ANA, dsDNA
• ANCA
• CXR / Mantoux
• VDRL/TPHA
• Toxoplasma IgG : 18.7 IU/ml (positive)
• Aqueous tap for CMV/HSV/VZV/Toxoplasma /TB PCR: not detected

NORMAL

• Obligate, intracellular parasite
• Commonest cause of retinochoroiditis and posterior uveitis
• Manifest between the 2nd & 4th decades of life
• Risk factors
• Immunodeficiency states
• Exposure to cats
• Eating raw or partially cooked meat
• Symptoms
• Blurred vision
• Floaters
• Pain
• Red eye
• Metamorphopsia
• Photophobia

• Iridocyclitis
• Unifocal superficial necrotizing retinochoroiditis
• Classical presentation involving inner retina
• Surrounded by oedema with contiguous inflammation of choroid and sclera
• May be a/w dense vitritis "headlight in the fog"
• May be a/w adjacent focal vasculitis kyrieleis arteriolitis
• Jensen’s papillitis
• Involvement of optic nerve from adjacent juxtapapillary retinitis
• Optic nerve sheath may serve as a conduit for the direct spread of Toxoplasma into the optic nerve from an adjacent cerebral infection  optic neuritis/papillitis
• Punctate outer retinitis -rare
• Deep retinitis - rare

• Ocular inflammation without necrotizing retinochoroiditis
• Retinal and optic nerve neovascularization, usually regresses with resolution of inflammation.
• Exact aetiology not well understood
• Retinal ischemia associated with severe retinal vasculitis
• Inflammatory reaction

Immunocompetent adults:

• Unilateral, painless. unifocal
• Vision good if macula not involved

Neonates:

• Congenital toxoplasmosis
• Bilateral, severe
• 70% retinochorioditis
• ⅔ macula involved a/w severe visual loss
• Micorophthalmia, vitritis, glaucoma, ocular palsies

Immunocompromised:

• Bilateral, multifocal, severe
• May be a/w SOL of CNS  Ocular palsies, nystagmus, VF defects

• Bactrim 11/11 bid x 1/12
• Prednisolone 1mg/kg (50mg od) tapered over 2 weeks

IgG:

• IgG seroconversion 2-4 weeks after systemic infection, peak titres 4-6 weeks after infection
• Titres maintained at high levels for many months or years.
• Recent infection : 4x rise in antibody titres over a 2-4 week period
• Clinical signs may develop before seroconversion occurs, or after peak titres have developed.
• A single antibody titre is difficult to interpret and is rarely of any value

Negative IgG excludes ocular toxoplasmosis

IgM

• Less value than IgG
• A negative IgM test excludes recent infection
• A positive IgM test is difficult to interpret because Toxoplasma-specific IgM antibodies may be detected up to 18 months after acute acquired infection

Goldmann-Witmer coefficient

Ratio of Toxoplasma IgG [eye] : [serum] > 3 is generally accepted as being consistent with active ocular infection

• But invasive procedure!

Aqueous humor and serum immunoblotting for immunoglobulin types G, A, M, and E in cases of human ocular toxoplasmosis. J Clin Microbiol. 2004 Oct;42(10):4593-8.

• Presence of T. gondii in ocular fluids is detected on PCR considered to be confirmation of active eye disease
• A negative finding does not exclude ocular toxoplasmosis
• Real-time PCR (Light-cycler, LC-PCR) more sensitive than nested PCR (n-PCR).

Evaluation of a Real-time PCR-based assay using the lightcycler system for detection of Toxoplasma gondii bradyzoite genes in blood specimens from patients with toxoplasmic retinochoroiditis. Int J Parasitol. 2005 Mar;35(3):275-83. Epub 2005 Jan

• Triple drug therapy :pyrimethamine, sulfadiazine, prednisolone
• Quadruple therapy : pyrimethamine, sulfadiazine, clindamycin, prednisolone.
• Bactrim (2 tabs bid) is as effective as pyrimethamine/sulfadiazine for lesions outside fovea.
• 61% in classic triple therapy grp vs 59% in Bactrim grp

Soheilian et al. Prospective randomised trial of Trimethoprim/sulfamethoxazole vs pyrimethamine & sulfadiazine in the treatment of ocular toxoplasmosis. Ophthalmology. 2005 Nov;112(11):1876-82

• At least 6 weeks treatment
• Others: Azithromycin + pyrimethamine (AJO 2002;134:34-40)

Spiramycin (Klin Montasbl Augenheildk 1998;212:84-7)

Atovaquone (hydroxynaphthoquinone) (Ophthalmology 1999;106:148-53)

Allopurinol (Adam et al. Berlin 2000)

• Corticosteroids
• Topical : depending on AC reaction.
• Depot absolutely contraindicated
• Risk of rampant necrosis and blind, phthisical globe
• Systemic adjunct to minimize collateral damage from the inflammatory response
• Usually from Day 3 @ 1mg/kg, tapered over 2 weeks

A presentation by

The Eye Institute @

Tan Tock Seng Hospital