help with sick cactus in AK

[cactiinAK]

Hello from the 49h state -
I have a cactus I've been growing for 20 years. All of a sudden it's started to turn brown from the bottom up (see picture). I don't know what kind it is, but looks like it has some new growth along with the parts that are dying. What can I do to help this poor thing?!

Thanks!

[greenknight]

Not a cactus, it's a Euphorbia - probably E. trigona. Browning of the old stems is common with these, if that's the only symptom it may not be sick at all. Take a look at the gallery here: https://davesgarden.com/guides/pf/go/57020/