Germanwings A320 crashes in France

[True Federalist (진정한 연방 주의자)]

The co-pilot's friends told Der Spiegel he battled depression in 2009 and took a 6-month leave from training. While he passed all physical and psych tests, German law prohibits Lufthansa from obtaining his previous medical history.

Lubitz's former classmates told reporters in Germany that the 28-year-old temporarily left pilot training due to "burnout-syndrom" [sic], ...

Why is the adverb "sic" used in that sentence? I know what it means, but I don't understand the usage here.

"Syndrom" is not a word

More precisely, it's not a word in English.

Or perhaps it's a complaint about the use of Denglisch.  Or the fact that in German it should be "Burnout-Syndrom" rather than "burnout-syndrom"