That is really hard to diagnose, sorry to say. It might be scale. Just guessing though. I would quarantine it & hope new leaves grow out normally. If it were me, I'd remove the leaves with bumps on them. Then spray in the cracks (near the stem with rubbing alcohol mixed 50/50 with water.

Thank you for the advice! Here is a picture of the scarry-looking bumps on the larger leaves, in case that helps.

Does anyone else have an idea of what this might be?

Oh, I do think that's scale.

You should try rubbing it with a q-tip dipped in alcohol/water to see if it rubs off - if scale, it will come off.
If so, do as rosemariero already suggested.

Rina

This post was edited by rina_ on Wed, Mar 5, 14 at 1:26

Hi Rina, that's a great tip, I'll have to remember that. It did not come off, so on the bright side it isn't scale, but it does leave me wondering what it could be. Is there any kind of mechanical damage that looks like that?

It has been suggested that the 'bumps' on jade plant may be caused by Oedema
Maybe same could occur on echeveria??? - I could be wrong...

(from garden guides)
Oedema is a disorder in jade plants that causes the roots to take up water faster than the plant can make use of it. This excess water builds up in the leaves and stems of the plant, creating small blisters that will swell and create corky, warty spots on the plant. If the plant has a severe case, these spots may develop on the flowers as well. If you increase your jade plant's light exposure and move it to a place where the air circulates better so that the environment is not so humid, it will probably get over the oedema on its own. Try watering less frequently also. You can wait until the lower leaves get soft and even a little wrinkled before giving your jade plant a drink.

Read more: Diseases in Jade Plants : Garden Guides http://www.gardenguides.com/101508-diseases-jade-plants.html#ixzz2v8nsZB9v

Rina

This post was edited by rina_ on Wed, Mar 5, 14 at 20:24

I just read this on webpage of Royal Horticultural Society-you can read more at: https://apps.rhs.org.uk/advicesearch/profile.aspx?PID=637#section1

All plants can be affected by oedema a condition brought on by overwatering or high humidity. It can be particularly troublesome on cacti, camellias, eucalyptus, fuchsias, pelargonium, succulents and vines.

Rina

This post was edited by rina_ on Wed, Mar 5, 14 at 20:30