Abstract
Background
Toxoplasma gondii is thought to infect up to a third of world’s population. Incidence rate of 0.4/100,000 has been calculated in Britain, culminating in a life-time risk of 18/100,000. Cats are primary hosts, but humans and warm-blooded animals can be infected by consumption of contaminated food/water. Although in most patients, it’s self-limiting, it can be devastating in immunosuppressed patients and may cause eye manifestations, cerebral abscesses or disseminated infection. Immunosuppressive therapies including treatment with biologics increases the risk and may also cause toxoplasmosis reactivation.
Methods
This is case of 57 year old lady with psoriatic arthritis. She has past history of congenital vision impairment in the left eye and is HLA B27 negative. She enjoyed horse-riding and had a pet dog. Initially she was started on methotrexate. Sulfasalazine was added later. Due to ongoing active disease, etanercept was used for 6 months, before being switched to cetrolizumab due to ineffectiveness. She had this for 5 months and then switched to infliximab, 3mg/kg, 8 weekly. In May 2019, she was seen by Ophthalmology for 2 weeks history of blurred vision and floaters in right eye. She was diagnosed to have panuveitis and had positive IgM for toxoplasma. Bloods revealed negative TB screen, HIV, Hep B&C, syphilis, lyme and anti-streptolysin antibody tests were negative. Infliximab levels were sub-therapeutic. She was commenced on 30mg prednisolone for possible inflammatory process secondary to seronegative arthropathy, but acute toxoplasmosis could not be excluded. Hence, she was started on azithromycin and had vitreous biopsy. Toxoplasma was detected in the sample, confirming acute infection. Methotrexate and infliximab were stopped. MRI head ruled out intracranial involvement. Following treatment of acute toxoplasmosis, adalimumab is now being considered for management of her inflammatory disease, with close monitoring by local infectious-disease team and specialist ophthalmology unit.
Results
This lady developed ocular toxoplasmosis and panuveitis, whilst on immunosuppression for psoriatic arthritis. She was a horse-rider and had exposure to dogs. Diagnosing toxoplasma in immunocompromised can be difficult. Isolation of T. gondii in tissue usually confirms diagnosis. Some forms of immunosuppressive treatment may be associated with increased risk of reactivation of toxoplasmosis but there is not much evidence to assess the relative risk of various therapies.
Conclusion
Ocular toxoplasmosis needs to be considered in patients receiving immunosupression and presenting with inflammatory eye symptoms. Management requires specialist input and close monitoring. Further research into diagnostic techniques, possibility of using prophylaxis in high-risk patients and management guidelines would be helpful.
Disclosures
M. Malik None. H. Anver None. E. Wong None.
Ocular Toxoplasmosis: Mechanisms of Retinal Infection and Experimental Models
