The skin lining the ear canal sheds like anywhere else on the body. The ear canal has a self-cleaning mechanism whereby this shed (desquamated) skin migrates or slowly moves towards the outside very much like a conveyor belt. Once it reaches the external ear opening, it falls of.
If this mechanism is interfered with, for example by a bony growth (like an osteoma) or there is hard impacted wax blocking the ear then the shed skin keeps accumulating in the ear and starts to expand. As it expands it destroys the bone around it very much like a benign tumor. It also secretes certain chemicals that destroy the bone around it. It has been postulated that patients who develop this condition may have abnormal epithelium that tends to multiply very rapidly. The process continues, till an infection develops. Then the ear may become very painful and may start to discharge and bleed.
Examination with otoscope or endoscope will show an expanded ear canal full of keratin. In the presence of an infected the ear canal may be very swollen, painful and stenosed particularly just proximal to the keratosis. Thick layers of keratin (much like the layers of a onion) with pus and granulation tissue may be seen.
A CT scan of the temporal bone may be done in some cases to rule out any other pathology. In keratosis obuterans the ear canal will appear expanded and eroded.
Treatment is to remove the keratosis. It may be done in the clinic under local anaesthesia with microscopic guidance. In some cases, a general anaesthesia may be necessary.