Feather follicle cysts appear as oval or elongated nodules, lumps or masses which contain an accumulation of yellow-whitish material (known as keratin). They can develop as a result of an infection, previous trauma to the feather follicle, or any condition that interferes with normal feather growth. Common causes of feather follicle cysts in chickens include:
- Previous trauma or damage to feathers
- Genetic predisposition (such as the Silkie breed, due to their soft, downy feathers)
- A defect in the cells
- Blockages of ducts in the body which cause a fluid build-up
- Chronic inflammatory conditions
If damage occurs on just one side of the follicle, it can cause asymmetric feather growth, in which it is not able to break through the skin. As a result, it will curl back within the follicle and fill with keratin, instead of producing a feather.
Feather follicle cysts can usually be diagnosed by your vet through clinical signs and the mass appearance. However, additional diagnostics may be needed in some cases. A cytology of the cyst in question usually contains erythrophagocytosis, erythrocytes, mixed-cell inflammation with an increased amount of background debris, multinucleated giant cells and/or the presence of feather fragments.
The treatment for feather follicle cysts varies depending on it's location, size, and impact on the bird's comfort level.