A person can suffer from Mushroom Syndrome in any way; the only circumstances are:
(1) A person doesn't tell you everything about a certain situation concerning you/and or them
(2) They tell lies.
Bree: OMG! He gave me Mushroom Syndrome! It turns out he was actually gay, which he never told me about.
Sarah: Wow! So what did he bullshit to you about? You know, the other half of the Mushroom Syndrome?
Bree: Oh, he told me he didn't break the blender but it *actually* was him!