Sometimes we have a plant stem that just doesn't look right. There might be something white or fuzzy about the stem, but it doesn't look like a plant disease. It may be corky scab or edema. This occurs when the plant takes up too much fluid and it can't get rid of it through transpiration. While not terribly harmful to your plant, it can make it look sick.
Edema won't actually be fuzzy. If that happens, it's more likely a fungal infection.
The best steps you can take to protect your plants from edema are to reduce watering, let the first few inches of soil dry out between waterings, and lower humidity within your growing space. These can be especially important points for growers that are trying to over winter plants in a greenhouse or inside the home, places where humidity levels can get very high and evaporation rates very slow due to the lack of air exchange.
We experience this problem with orchid cactus. Excess moisture will cause the leaves to develop boils which eventually rot and destroy the leaf.