It is not uncommon for certain dermatoses to present in similar ways, even though they are fundamentally different. Among them, pityriasis versicolor, a fungal infection, and vitiligo, an autoimmune disease, are often confused due to their similar effects on skin pigmentation. However, it is essential to distinguish between them in order to implement an appropriate treatment. Here are some identification keys.
Pityriasis Versicolor: How to differentiate this fungal infection from vitiligo?
Summary
Published on November 25, 2024, by Pauline, Chemical Engineer — 8 min of reading
Themes:
Pityriasis Versicolor and Vitiligo: A Brief Overview of These Dermatoses.
Pityriasis versicolor is a fungal infection caused by the colonisation of the skin by yeasts of the Malassezia genus, which are lipophilic microorganisms. Certain factors, such as high humidity or weakened immunity, can promote the onset of this disease. Pityriasis versicolor results in the appearance of finely scaly spots, the colour of which varies from yellow to brown, with a subtle erythema. It should be noted that this mycosis is benign and non-contagious.
In comparison, vitiligo is an autoimmune disease characterised by the destruction of melanocytes, the cells responsible for skin pigmentation. This progressive loss of melanocytes leads to the appearance of well-defined white patches, often symmetrical, on various parts of the body. Vitiligo is linked to a genetic predisposition and triggering factors, such as oxidative stress, skin trauma, or immune imbalances. Furthermore, vitiligo is often associated with other autoimmune diseases, such as dysthyroidism or type 1 diabetes.
What are the differences between vitiligo and pityriasis versicolor?
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.
| Criteria | Vitiligo | Tinea Versicolor |
|---|---|---|
| Location of Lesions | Can affect any region, often with a symmetrical distribution. Common areas: hands, feet, face, elbows, knees. | Areas rich in sebaceous glands: upper back, chest, shoulders, neck. |
| Distribution of Lesions | Symmetrical (non-segmental form) or unilateral (segmental form). | Asymmetrical, often confined to the seborrheic areas. |
| Appearance of Lesions | No flaking or inflammation. Well-defined white spots, skin smooth and normal to the touch. | Presence of a fine desquamation visible after scratching. Colour variation depending on the phototype: hyperpigmented, rosy or depigmented. |
| Associated Symptoms | Generally asymptomatic, but itching may occur during an active phase. | Mild itching may occur, especially in conditions of heat or humidity. |
| Progression of Lesions | Permanent lesions without intervention. Unpredictable progression, with possible widespread extension. | Potential disappearance after antifungal treatment. The spots may temporarily persist after sun exposure. |
| Differential Diagnosis | White fluorescence under a Wood's lamp, revealing a lack of melanin. | Yellow-green fluorescence under Wood's lamp, indicating the presence of Malassezia. |
| Management | Immunomodulatory approach, UVB phototherapy or specific topical treatments. | Local or systemic antifungal treatment. |
Tableau récapitulatif des critères d'identification du vitiligo et du pityriasis versicolor.
Sources
BIGBY M. & al. Pityriasis Versicolor: A Systematic Review of Interventions. Archives of Dermatology (2010).
RENATI S. & al. Pityriasis versicolor. British Journal Medical (2015).
BORRADORI L. & al. Dermatologie et infections sexuellement transmissibles. Elsevier Masson (2017).
EZZEDINE K. & al. Vitiligo: A Review. Dermatology (2020).
HARRIS J. & al. Vitiligo: Mechanisms of Pathogenesis and Treatment. Annual Review of Immunology (2020).
HAMIDA T. & al. Vitiligo en association avec les maladies auto-immunes : série de 293 cas. La Revue de Médecine Interne (2024).
