Pityriasis versicolor is often called tinea versicolor; pityriasis is the correct term because it is caused by a yeast and not a dermatophyte.

What does it look like?

Patients with pityriasis versicolor usually present with light or dark spots that are round or oval in shape and vary in size from a few mm diameter to about 1cm in diameter. The surface of each macule has faintly visible scale or scale that can be seen after the macule is scratched lightly. The macules are classically found on the upper back and chest, but can be on the arms, abdomen, legs, and face as well.  

What causes it?

Pityriasis versicolor is caused by the yeast Malassezia furfur.  M. furfur is a normal resident on the skin and only causes problems when it overgrows. The yeast can overgrow in certain favorable conditions: high humidity, oily skin, treatment with steroids, and excess sweating. This condition can be as seen in as many as 20% of the population in tropical and subtropical areas.

How is it diagnosed?

Like dermatophyte infections, pityriasis versicolor is diagnosed clinically and confirmed with a KOH preparation if necessary. The yeast forms are much smaller than those seen in tinea and it is possible to see both spores and rounded hyphae (often said to resemble “spaghetti and meatballs”) on the slide. This is different from tinea infections where long branching hyphae are seen. It is easiest to see the yeast at 40x power.

Is it contagious?

Not really. Since the yeast is present on everyone’s skin already, touching someone with pityriasis versicolor doesn’t increase the chances of having the condition.

How is it treated?

Selenium sulfide is the topical treatment of choice and either a lotion or shampoo can be used. The selenium sulfide must be left on for 10-15 minutes once a day before being washed off and should be used daily for 2 weeks. Patients may choose to use the shampoo or lotion once every few weeks on an ongoing basis because patients can relapse as the factors that led to the overgrowth of yeast are likely to be present in the future. It can also be treated with oral antifungals. Itraconzaole 400 mg in a single dose has proven effective, as has 300 mg fluconazole with a repeat dose at 2 weeks. With oral therapy, the effect is enhanced if the patient exercises to the point of a slight sweat 30 minutes after taking the medication and then waits overnight before showering. It is important to note that the scale and pruritus should resolve immediately after treatment, but the pigment change can take months to return to normal.

What is the differential diagnosis?

Pityriasis alba (see Ch. 13): This is a form of mild eczema where the skin is hypopigmented and slightly scaly. There is occasionally a tiny bit of associated redness. These areas are usually dry and there is often a history of eczema. The patches are usually larger and more ill-defined compared to pityriasis versicolor. It is most common on the face.

Vitiligo (see Ch. 13): This is typically characterized by white patches with complete loss of pigment (depigmentation) compared to the light patches with partial loss of pigment often seen in pityriasis versicolor (hypopigmentation). In vitiligo, there is no scaling associated with the white patches and they tend to occur bilaterally and in specific areas (e.g. around the eyes, on the hands/feet, and in the groin). The size of the patches is variable from small confetti-like dots to virtually the entire body.

Post-inflammatory hypopigmentation (see Ch. 13): After a rash improves, the area can be left either light (hypopigmented) or dark (hyperpigmented). Usually there is a history of rash which precedes the pigment change in these cases.

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