Pityriasis Versicolor: How to differentiate this fungal infection from vitiligo?

Distinguishing between vitiligo and pityriasis versicolor is the first step towards establishing an appropriate treatment plan. While only a dermatologist can make an accurate diagnosis, certain elements can help to differentiate these two diseases.

• Observe the location and distribution of the lesions.

  Pityriasis versicolor lesions typically concentrate on areas rich in sebaceous glands, such as the upper back, chest, shoulders, and neck. These seborrheic areas promote the proliferation of yeast Malassezia, which is responsible for the infection. In some patients, the macules may slowly migrate, forming irregular patterns, but they remain confined to the seborrheic regions.

  Unlike pityriasis versicolor, vitiligo can affect any area of the body. The white patches often follow a symmetrical distribution, although the segmental vitiligo, which is less common, presents unilaterally. Vitiligo frequently affects the hands and feet, the face, particularly around the eyes and mouth, and areas exposed to friction, such as the elbows or knees.

• Detail the appearance of the lesions.

  The macules of pityriasis versicolor present a fine scaling that may not be visible to the naked eye but becomes apparent after light scratching. Furthermore, the lesions may exhibit a variation in colour depending on the individual's phototype or sun exposure. In people with light skin, they are often hyperpigmented or rosy, while in people with dark skin, they appear depigmented.

  Vitiligo lesions, on the other hand, do not cause any changes to the skin's texture. The affected skin remains smooth and normal to the touch, without any flaking or inflammation. The spots are white, well-defined, and contrast sharply with the surrounding skin, particularly in individuals with dark skin.

• Questioning the associated symptoms.

  The lesions of pityriasis versicolor can be accompanied by a mild itch, particularly in cases of heat or humidity. This symptom is due to the activity of the yeasts Malassezia, which release substances that irritate the skin. However, this is not always the case. Vitiligo is generally asymptomatic when it is in its inactive phase, but itching can be a precursor to new white spots.

• Tracking the progression of lesions.

  Pityriasis versicolor lesions are dynamic and can fade within a few weeks of development, particularly following sun exposure. However, after appropriate treatment, they disappear without leaving any marks. The progression of vitiligo, on the other hand, is difficult to predict, with the condition potentially remaining localised or gradually spreading to other parts of the body, or even becoming generalised. Continuous management of the vitiligo is necessary to stabilise the lesions.

• Consult a dermatologist.

  Dermatological diagnosis remains the only method that can definitively differentiate between pityriasis versicolor and vitiligo. This is typically a clinical diagnosis and rarely requires a biopsy. It is often conducted using a Wood's lamp, a radiation device that emits long UVA and violet-blue light. In the case of pityriasis versicolor, it emits a yellow-green fluorescence, due to the presence of Malassezia yeasts. If it is vitiligo, the lamp emits a white fluorescence, revealing an absence of melanin.