Pemphigus Foliaceus
Pemphigus is an immune mediated skin disorder involving the inappropriate immunological attack against one of the normal layers of skin. There are different types of Pemphigus however the only difference between them is which layer of skin is being attacked.
The outer layer of skin is called the epidermis and consists of cells arranged in layers with the newer cells at the bottom and the older dying cells at the top. There are 4 main types of cells making up the epidermis they are keratinocytes (what we refer to as skin cells), melanocytes (whish produce pigment and gives us a sun tan), Langerhans’ cells (these are part of the immune system), and Merkel cells (these are what notify the nervous system when we are being touched).
Now lets look are the layers of normal skin starting at the bottom:
The basal layer is where new keratinocytes are produced. These new skin cells divide here and as the reproduce a structural protein known as keratin is made. The cells are pushed farther and farther up through the skin until the die and form the outer skin. There are also Merkel cells and melanocytes located in the basal layer that is one cell thick.
The spinous layer or “prickle cell layer” is a 1-2 cells thick layer that is comprised of basal cells that have divided and moved up. These cells appear to have little “prickles” connecting them, which is where the name comes from. Langerhans’ cells live in this layer of the skin.
As cells continue to divide they move up to the granular layer, which is named for what appear to be granules inside of the cells. This layer is also usually 1-2 cell thick but it is thicker around hair follicles.
Cells that have died and fully keratinized form the clear layer. These cells are flat and tough to help form an extra layer of protection. This layer is only present in footpads and the leather of the nose.
If you look down at your skin the layer that is visible is called the horny layer. These cells are dead, fully keratinized, and overlap in flat plates. The main purpose for these cells is to form a barrier against the environment. These cells slough off with friction and motion, this cell loss being balanced by the production of new cells in the basal layer.
Pemphigus Foliaceus is a condition in which the attachment of the granular cells to one another is attacked by the immune system. This is the most common immune mediated skin disease in dogs and cats. The separation of these granular cells cause crusts and ulcers to form particularly at the places where haired and non-haired skin meet such as the ears, eyes, footpads, noses, and groins. Cats can also form lesions at the beds of the toenails causing crusty painful feet.
A small biopsy of the skin is the most reliable way to diagnose pemphigus. For this procedure a small section of affected skin is removed and sent a pathologists for identification of the disease process. In some cases this procedure can be performed under a local anesthetic however in cased where the nose or face needs to be sampled general anesthetic is usually needed.
The treatment for pemphigus foliaceus is to suppress the immune system. In approximately 50% of patients this is achieved through the use of high doses of corticosteriods. Antibiotics are also needed in many cases to control secondary infections that often develop. In some cases anti bacterial and anti fungal shampoos are also helpful. Due to the high doses of steroids used to treat this disorder side effects are common. These are typically increased thirst, increased urination, animals often tend to have an increased appetite, and also gain weight. Dogs on high doses of these medications can also develop a tendency to pant more.
For dogs that cannot tolerate these high doses of steroids or those that do not respond to this treatment a stronger immune suppressant is available in a medication called azathioprine. Unfortunately it can take up to 2 months to see any noticeable effect from this medication and the steroids must be continued for this time. Azathioprine also has the potential to cause blood marrow suppression and for this reason blood work is often need every 2 weeks during initial treatment.
Treatment for this condition is typically slowly tapered down after the lesions have been cleared up and the patient is stable. Many dogs will ultimately stop all treatment permanently but it usually takes several months to get to that point. It is also important to realize that this condition requires time and patience and just because rapid response is not noted does not mean the pet will not respond at all.