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Relapses of myelitis and optic neuritis following H1N1 vaccination

Background: Although it has been well established that vaccination does not increase the risk of relapse in patients with multiple sclerosis (MS), no study on the influence of immunization on neuromyelitis optica spectrum disorder (NMOsd) has been conducted. As NMO differs from MS in a number of aspects, including its immunopathogenetic mechanisms, vaccination may have some influence on the occurrence of new relapses. Recently H1N1 vaccine has been introduced in many countries in association with a massive vaccination program. Therefore, it is highly desirable that patients at risk of more severe adverse effects and complications might be identified. Objective: To report two NMOsd patients who developed relapses following H1N1 vaccination. Case 1. A 26-year-old mulatto female with a history of hyperprolactinemia and hypothyroidism had two episodes of transverse myelitis in March and August 2008 with full recovery following treatment with IV methylprednisolone. Spinal MRI showed a gadolinium-enhanced centromedular C2 to C7 lesion. Serum positive autoantibodies included ANA, antiocardiolin, rheumatoid factor, anti-thyroid peroxidase and antiacethylcholine receptor antibodies. NMO-IgG was negative. In April 2010 she developed an acute attack of paraparesis and dysesthesia in the lower limbs two weeks following H1N1 vaccination. She had full and spontaneous recovery few days later. Case 2. A 17-year-old white female developed pain and blurred vision in the right eye. Three weeks later she experienced weakness and loss of sensation in the four limbs. She was given IV methylprednisolone with full recovery. Visual acuity was 20/20 OU but there were mild dyschromatopsia and contrast sensitivity loss in the right eye. Spinal MRI disclosed a T2-lesion from C2 to C8. Brain MRI showed a few periventricular hyperintensities. CSF examination was normal and serum NMO-IgG was negative. The patient was put on azathioprine and was doing well with no relapse for the six-months-follow-up-period when she developed pain and blurring of vision in the right eye one week following H1N1 vaccination. Examination showed visual acuity OD 20/60, OS 20/20. Spinal cord function remained unchanged. Conclusion: The present cases meet criteria for diagnosis of NMOsd in spite of being NMO-IgG seronegative. Although both of them developed relapses within two weeks following H1N1 vaccination the relationship between the vaccination and relapses in these cases remain unclear.

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