The letter explicitly states the date of your next flight physical (which is probably not the same date as your next special-issuance certificate renewal)
13: This paragraph is very important.
The only condition that every airman must actually report promptly – within 60 days of legal action – is an alcohol-related incident. This paragraph adds to the FARs by requiring any adverse change in your medical condition be reported “promptly”. There is no guidance on “prompt” but it's probably reasonable to use the alcohol-related definition as a guide.
This wording is ambiguous regarding “medical condition” – are we required only to report specifically changes in the medical condition for which we are receiving special issuance? Or does this paragraph require us to report promptly any change in our general health?
I don't think the FAA has the capacity to absorb all the reports this general reading would entail; I have always interpreted this paragraph as applying to the medical condition for which special issuance is granted by this letter.