CREST syndrome

Raynaud-hand2

CREST syndrome is one expression of a larger disease known as systemic sclerosis (or, if you’re stuck in your ways like me, “scleroderema”). (more…)

25 year-old male with rapidly-growing forearm mass

A 25 year-old male presents with a mass on the volar aspect of his forearm. He first noticed the lesion 2 weeks ago, when he developed pain in his arm, and since then it has grown rapidly to reach its current size of approximately 5 cm. (more…)

Mastocytosis

Mastocytosis is actually a spectrum of rare disorders, all of which are characterized by – not surprisingly – an increase in mast cells. (more…)

What’s the difference between pemphigus vulgaris and bullous pemphigoid?

Here are two diseases that are easy to confuse: pemphigus vulgaris and bullous pemphigoid.

Both diseases are characterized by bullae (big, blister-like skin lesions) and both have “pemphig” in their names (“pemphig-” comes from the Greek pemphix, meaning blister, so that makes sense). So what are the differences between the two?

Pemphigus vulgaris

Here’s the key to differentiating between the two disorders. “Pemphigus” is used in a very specific way (you’d think it would be used to describe any blistering disorder, but not so!). It is used to describe blistering disorders caused by autoantibodies against the connections between cells of the epidermis.

Pemphigus vulgaris, not surprisingly, is the most common type of pemphigus (“vulgar-” comes from the Latin vulgaris, meaning the general public). It occurs primarily in adults between the ages of 30 and 60, and is characterized by big, flaccid bullae that burst easily (in most patients, you’ll see more ruptured, scab-covered bullae than intact ones). Patients often present first with oral bullae and ulcerations, and later develop bullae on the skin.

In this disease, patients have autoantibodies against desmogleins, which are part of the spot desmosomes (intercellular junctions that connect cells of the stratum spinosum with each other). The antibodies mess up the desmosomes, disrupting connections between the squamous cells of the epidermis and causing very superficial, intraepidermal, fragile bullae.

If you do immunofluorescence on the skin, you’ll see a kind of outlining of each individual epidermal cell (because there are autoantibodies bound to the junctions between the cells). Treatment consists of immunosuppressive agents; prognosis is variable, but many patients have a higher than normal mortality rate.

Bullous pemphigoid

This disease is called pemphigoid rather than pemphigus, because it looks like pemphigus but really isn’t! In pemphigus, there are autoantibodies against the connections between epidermal cells. But in bullous pemphigoid, the are directed against hemidesmosomes (specialized intercellular junctions that attach epithelial cells to the basement membrane).

This means that the bullae are actually subepidermal, so they are less fragile than those of pemphigus vulgaris (if you see a patient with bullous pemphigoid, you’ll see lots of intact, tense bullae, rather than a bunch of ruptured bullae covered with scabs). The immunofluorescence pattern is correspondingly different – you’ll see just a line at the base of the epidermis (rather than the lace-like outlining of epidermal cells you see in pemphigus vulgaris).

Patients with bullous pemphigoid are generally elderly, and the clinical presentation varies a lot (but usually it doesn’t start in the mouth, like pemphigus vulgaris). It’s a less serious disease, usually, since the bullae often don’t rupture (so there’s less chance of infection and scarring).

Bottom line: if you can remember that pemphigus is a disease that has intraepidermal antibodies, then you can keep the clinical presentation and immunofluorescence pattern of the two diseases straight.

Neuroma vs. neurofibroma

Q. What is the difference between a neurofibroma and a neuroma?

A. A neuroma is a general term that applies to any of a number of different things (neoplastic or non-neoplastic) that make a nerve or nerve bundle swell. Usually, another word is attached to give more specific meaning.

Neoplastic neuromas are tumors of any part of a nerve (including the surrounding myelin); sometimes the term is used more broadly to refer to any tumor of neural tissue. An example of a neoplastic neuroma is acoustic neuroma, a benign tumor surrounding the 8th cranial nerve (you can also call this tumor a schwannoma, since it is a neoplasm derived from the Schwann cells surrounding the nerve, not the nerve itself).

The main non-neoplastic neuromas are traumatic neuroma (a non-neoplastic reaction of a nerve to some sort of damage) and Morton’s neuroma (which is not even a neuroma, but just an accumulation of fibrous tissue around a nerve, usually in the foot).

Neurofibromas are benign neoplasms derived from the myelin sheath of peripheral nerves (just as a reminder: the myelin surrounding peripheral nerves is supplied by Schwann cells; the myelin surrounding central nerves is supplied by oligodendrocytes). They often occur in the context of neurofibromatosis, a hereditary condition characterized by multiple cutaneous neurofibromas, pigmented skin lesions, skeletal abnormalities, macrocephaly, epilepsy, and a bunch of other findings. In the photo above, the patient has multiple neurofibromas scattered over his entire body.

Neurofibromas are like schwannomas, in that they are derived from schwann cells. However, a schwannoma has mostly just schwann cells in it, whereas a neurofibroma has a bunch of other cell types, like fibroblasts, endothelial cells, and mast cells.