Dr. Jeff Hersh: The skin is a complex system
Q: I recently read your column about epidermolysis bullosa and it sounded a lot like a disease my father was diagnosed with, bullous pemphigoid. What's the difference?
A: Excellent question!
To begin the discussion it is useful to review the anatomy of our skin.
The skin is made up of two major layers; the epidermis, which is the outer layer of the skin, and the dermis, which is the deeper, underlying layer.
The epidermis is the waterproof protective covering of the body. The epidermis itself has sub-layers, which range from the very top layer of dead skin cells (the ones a loofah sponge scrapes off) down to the junction where it is anchored (basement membrane). The dermis is the cushiony layer of the skin that contains the hair follicles, oil glands, sweat glands, blood vessels and nerves. Under the dermis lies the subcutaneous tissues where fat, connective tissue, larger nerves and blood vessels all reside.
Both bullous pemphigoid (BP) and epidermolysis bullosa (EB) affect the anchoring of the skin (and both can also affect the mucous membranes, such as the linings of the respiratory and GI tracts).
When the anchoring mechanism fails, the skin layers slip easily - one over the other - making the skin very fragile and predisposing it to blister and sore formation; the medical term for a large blister is a bullous. You can think of this as if the skin is receiving a hot water scald burn. You can imagine the problems that can arise from getting skin "burns" from even minor rubbing or pressure.
EB is inherited, so the patient is born with the skin defect. BP is an autoimmune disease; for unknown reasons the body's antibodies attack some of the basement membrane proteins.
It is theorized that certain medications (such as furosemide, non-steroidal anti-inflammatory medications such as ibuprofen, certain antibiotics and others), X-ray therapy, ultraviolet radiation or other triggers inappropriately stimulate the body's immune response in susceptible people.
BP is a rare condition, estimated to affect 10 to 20 people per million. The classic clinical scenario is the onset of widespread eruptions of blisters in a patient in their 50s to 70s who is on multiple medications. The blisters may be itchy, red and/or irritated.
There are actually many subtypes of bullous pemphigoid; some cases are associated with pregnancy (gestational pemphigoid), some associated with other diseases (such as lupus, psoriasis or others) and there are other subtypes as well.
A skin biopsy is done to verify the diagnosis, and direct immunofluorescence studies are usually done as well.
The goal of treatment of BP is to minimize blister formation, promote healing of the blisters that do form and to prevent complications.
Since BP is an autoimmune disease, treatment is aimed at minimizing the body's inappropriate immune response. Steroids are usually the first line of treatment. Recent studies have suggested that using steroid creams is actually more effective than taking steroid medications by mouth, although for those with very extensive skin involvement, covering all the lesions with steroid cream can be difficult and expensive. For patients that do not respond to steroid treatments, other immune system modifying medications may be used.
The most common complication of BP is infection, which can occasionally be severe and may even be fatal. Complications from the immune-suppressive medications are also common and can sometimes be severe as well.
BP will typically last five to six years or so, flaring up and remitting (usually with treatments) during this time. For patients who do well during this time, vigilance for possible future recurrences is key, although many patients do well without suffering further "attacks."
Although there are many similarities between BP and EB, they are two very distinct conditions with very different underlying causes and different prognoses. People with BP are usually treated by a physician with expertise in the condition, and consultation with such a specialist is a good idea.
Jeff Hersh, Ph.D., M.D., F.A.A.P., F.A.C.P., F.A.A.E.P., can be reached at DrHersh@juno.com.