If a patient had Momo (likely referring to a viral infection) in July, will the skin spot still be positive?

MOG-IgG Testing After Myelin Oligodendrocyte Glycoprotein Encephalomyelitis (MOG-EM)

MOG-IgG serum concentrations can transiently disappear after clinical recovery, particularly in monophasic cases, so a previously positive MOG test from July may now be negative depending on the clinical course and treatment status. 1

Factors Affecting MOG-IgG Detection Over Time

MOG-IgG serum levels are directly influenced by:

1. Disease activity:

   • Higher median concentrations during acute attacks
   • Lower concentrations during remission periods

2. Treatment status:

   • Lower concentrations while on immunosuppression
   • May transiently vanish after plasma exchange or IVIG treatment

3. Disease course:

   • In monophasic MOG-EM/ADEM: MOG-IgG may disappear permanently following clinical recovery, especially in adult patients 1
   • In relapsing disease: MOG-IgG tends to persist longer (detectable in all patients with relapsing disease in a study with mean follow-up of 33 months) 1

Time Course of MOG-IgG Persistence

• Monophasic disease: MOG-IgG often disappears after the initial attack, particularly in children and juveniles with ADEM 1

• Relapsing disease: MOG-IgG typically remains detectable at follow-up (in one study, it was detectable in all patients with relapsing disease for up to 10 years) 1

Implications for Testing

If the patient had MOG-EM in July and it's now several months later:

• If monophasic disease: The MOG-IgG test may now be negative, especially if the patient has recovered clinically
• If relapsing disease: The MOG-IgG test is more likely to remain positive

Important Considerations

• False negatives can occur: Titers may fall below cut-off temporarily following treatment with steroids, plasma exchange, immunosuppressants, or even spontaneously 1

• Transient seroconversion: Some patients show temporary conversion to seronegativity before becoming positive again at a later stage 1

• Re-testing recommendations: If MOG-EM is still suspected despite a negative test, re-testing is recommended:

  • During acute attacks
  • During treatment-free intervals
  • 1-3 months after plasma exchange or IVIG 1

Clinical Implications

• Prognostic value: Disappearance of MOG-IgG after the initial attack might have prognostic implications, potentially indicating a monophasic course 1

• Treatment decisions: It would be challenging to base long-term treatment decisions solely on whether MOG-IgG disappears after a first attack 1

• Monitoring recommendations: If long-term treatment is discontinued due to conversion to seronegativity, close monitoring of the patient's MOG-IgG status is highly recommended to confirm long-term seronegativity 1

Caveat

Before concluding a patient has "monophasic" MOG-EM based on negative antibody testing, remember that the interval between first and second attacks in relapsing MOG-EM can vary considerably, with the second clinical attack occurring after several years in some cases 1.