Case 3 : A Case of Ocular Toxoplasmosis

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Case 3 A Case of Ocular Toxoplasmosis

• Dr Johnson Tan
• Medical Officer
• Tan Tock Seng Hospital

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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

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On examination of RE,
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• What were the findings?
• 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

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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

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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
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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

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Ocular Presentations

• 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
• Jensens 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

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Uncommon Ocular findings

• 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

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Optic neuritis vs disc swelling from contiguous
spread?
Optic neuritis Disc swelling from contiguous spread
VA P
Colour P
RAPD P
VF
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Ocular Toxoplasmosis

• Immunocompetent adults
• Unilateral, painless. unifocal
• Vision good if macula not involved
• Neonates
• Congenital toxoplasmosis
• Bilateral, severe
• 70 retinochorioditis
• ? 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

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Follow-up

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

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Typical Presentation Course
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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

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Serological diagnosis

• 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 gt 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 Oct42(10)4593-8.

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PCR

• 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
  Mar35(3)275-83. Epub 2005 Jan

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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 grp
• Soheilian et al. Prospective randomised trial of
  Trimethoprim/sulfamethoxazole vs pyrimethamine
  sulfadiazine in the treatment of ocular
  toxoplasmosis. Ophthalmology. 2005
  Nov112(11)1876-82
• At least 6 weeks treatment
• Others Azithromycin pyrimethamine (AJO
  200213434-40)
• Spiramycin (Klin Montasbl Augenheildk
  199821284-7)
• Atovaquone (hydroxynaphthoquinone)
  (Ophthalmology 1999106148-53)
• 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 _at_ 1mg/kg, tapered over 2 weeks

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Thank you
A presentation by The Eye Institute _at_ Tan Tock
Seng Hospital