TromboneChat

I was preparing to put one of my horns in long term storage last night and brought out an old case that I thought was protected from the humidity. Upon opening it I found what looked like mold growth in it. Before I write the case off as a total loss, is there anyway to undo the growth and its effects? If its not advisable then I guess Ill be in the market for a case.

There is no chance of getting rid of the mold, in my experience. Throw it away.
Cases need to be stored in a VERY dry environment, and probably open. Once mold starts it's pretty much too late.

There is one possibility, if you have some free time on your hands and are feeling crafty. The case looks like the molded plastic student-type. If so, you could pull the lining out, unscrew any wood pieces and cut duplicates before throwing them out, and scrub the plastic shell with some anti-fungal cleaner. Setting it in the warm sun afterwards couldn't hurt either. Then, refine with whatever type of fabric you like. You could also re-,position any wood pieces to get a better fit, if needed.
Of course most sane people would just chuck it and buy a new case, but I have never fit that definition anyhow.