Discolored round spots on your upper body?

Tinea versicolor affecting the face of a patient. Here it presents as light spots against the pigmented skin. Photo credit: Grook Da Oger
Tinea versicolor affecting the face of a patient. Here it presents as light spots against the pigmented skin. Photo credit: Grook Da Oger

If you’ve noticed the appearance of discolored, round/oval-ish spots on your body, especially during the humid seasons, you may be dealing with tinea versicolor, aka pityriasis versicolor.  This is a condition where a yeast called Malassezia grows in the top layer of your skin.  This yeast especially likes warmth and humidity, so it is more common during the humid summer months or in those who work our a lot (e.g. athletes).  You may notice that this rash goes away during the dry cool months only to return when summer returns.  The spots may be light or dark, pink, tan, or brown, depending on your skin type.  They may be slightly scaly and itchy.  The rash favors the upper back/chest, shoulders, upper arms and neck but may also affect other areas such as the face.

How do you diagnose tinea versicolor? Your physician can make the diagnosis by examining your rash. She/he may also scrape the rash and look at the scrapings under a microscope.  If you have tinea versicolor, it will be easy for your physician to see the organism under the microscope.

This is a skin scraping from a patient with tinea versicolor showing the yeast Malassezia.
This is a skin scraping from a patient with tinea versicolor showing the yeast Malassezia.

So how do you treat tinea versicolor?  Your physician may recommend a topical shampoo, lotion or cream. Some of these are available over the counter, e.g. Selsun Blue shampoo, Nizoral shampoo, pyrithione zinc containing washes or soap bars, etc.  Several of these products are marketed as anti-dandruff shampoos, washes, soaps at your local drugstore.  You may also be prescribed a topical shampoo/wash, lotion or cream. If severe, your physician may prescribe a pill for you to take.  Also, taking care to towel off and shower after sweating or exercising is a good idea.

What is the indirect immunofluorescence test?

I hope you found yesterday’s post on the direct immunofluorescence (DIF) test on skin biopsies helpful.  Today, we will cover the indirect immunofluorescence (IIF) test.  This IIF test is a way to find whether a patient’s blood contains antibodies.  In the case of autoimmune blistering disorders such as pemphigus vulgaris, bullous pemphigoid or paraneoplastic pemphigoid, we are looking for autoimmune antibodies (autoantibodies) to one’s own skin.

For the indirect immunofluorescence test, the patient’s blood is drawn and submitted to the pathology lab (NOT the patient’s skin). In the case where autoimmune blistering diseases are suspected, the pathology lab takes the serum of the blood to see if it has antibodies that bind to certain cells or tissues.  The lab then adds an antibody which is fluorescently labeled that can bind to the suspected antibodies.  In autoimmune blistering diseases, different tissues may be used by the pathology lab, e.g. rat bladder, guinea pig esophagus, monkey esophagus, etc.  Some tissues are more sensitive or specific for a certain disease.

What is the direct immunofluorescence test on a skin biopsy?

Image by Wikipedia user Kauczuk. DIF of Henoch-Schonlein Purpura shows IgA around the vessels of the skin dermis.
DIF of Henoch-Schonlein Purpura shows IgA around the vessels of the skin dermis. Image by Wikipedia user Kauczuk.
This biopsy showed a positive "lupus band" test. Note the granular fluorescent deposits between the epidermis and dermis. Image from Wikipedia user Magnus Manske.
This biopsy showed a positive “lupus band” test. Note the granular fluorescent deposits between the epidermis and dermis. Image from Wikipedia user Magnus Manske.

Normal skin biopsies get sent for hematoxylin and eosin staining (or what we call H&E staining).  However, for certain skin conditions, we do a special test.  We take a skin or oral biopsy for direct immunofluorescence (DIF) examination.  These conditions that we are looking for may include blistering diseases such as pemphigus vulgaris, pemphigus foliaceus or bullous foliaceus, or non-blistering diseases such as lupus or Henoch-Schonlein purpura where one is looking for a specific vasculitis (inflammation around blood vessels).

So how is the direct immunofluorescence (DIF) exam done? First, a biopsy of skin or the oral mucosa is taken.  Next, it is sent to the pathology lab where the skin is cut into small slivers and mounted onto a glass slide.  Antibodies which have fluorescent tags on them are then thrown into the mix with this tissue.  These antibodies that the pathology lab adds to the tissue may recognize other antibodies (e.g. IgA, IgM, IgG) or other products such as C3 or fibrinogen.  Because the pathology lab’s antibodies have fluorescent tags, the pathologist can then see whether the fluorescence forms a specific pattern. For instance, the fluorescence may be brightest around the vessels (e.g. as in Henoch-Schonlein purpura), between the epidermis and dermis at the basement membrane (e.g. as in bullous pemphigoid), or between the cells of the epidermis (e.g. as in pemphigus vulgaris).  Even a test which is negative may be helpful, since the negative test sways us away from certain diagnoses such as the ones we had listed above.  For instance, we’d expect a disease such as a genetic epidermolysis bullosa (EB) to have a negative DIF.

Hope that helps you interpret your pathology biopsy report.  Stay tuned to future posts to learn how indirect immunofluorescence (IIF) differs from direct immunofluorescence!