Case 3 : A Case of Ocular Toxoplasmosis

Dr Johnson TanMedical Officer

Tan Tock Seng Hospital

Mr SCHA

17/Chinese/male

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 +

On examination of RE,

What were the findings?

1. Rt superior optic disc swelling superiorly

2. Superior-temporal peripapillary white lesion with indistinct edges

3. Adjacent vasculitis

What would be the next step? Take a full history

Further questioning… 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

Investigations

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

Ocular Toxoplasmosis 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

Ocular Presentations1. Iridocyclitis2. 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

3. 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

4. Punctate outer retinitis - rare5. Deep retinitis - rare

Uncommon Ocular findings

6. Ocular inflammation without necrotizing retinochoroiditis

7. 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

Optic neuritis vs disc swelling from contiguous spread?

Optic neuritis Disc swelling from contiguous spread

VA ±

Colour ±

RAPD ±

VF ± ±

Ocular ToxoplasmosisImmunocompetent 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

Follow-up

Bactrim 11/11 bid x 1/12

Prednisolone 1mg/kg (50mg od) tapered over 2 weeks

Typical Presentation & Course

Serological diagnosis

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

Serological diagnosisIgMLess value than IgG

A negative IgM test excludes recent infectionA 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 coefficientRatio 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.

PCR

Presence of T. gondii in ocular fluids is detected on PCR considered to be confirmation of active eye diseaseA 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

Treatment: Updates 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 grpSoheilian 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

Thank you

A presentation byA presentation byThe Eye Institute @Tan Tock Seng Hospital