Differentials
Vitiligo
SIGNS / SYMPTOMS
Primarily affects acral areas of the body such as the hands and feet, as well as the face. Depigmented, rather than hypopigmented, lesions with no associated scale.
Highlighting of depigmented areas with Wood lamp viewing but no fluorescence in lesions of vitiligo. In addition, vitiligo is usually distributed in a symmetric pattern, whereas the hypopigmented lesions of PV may or may not be symmetric.
INVESTIGATIONS
Microscopy: negative with potassium hydroxide (KOH) preparation.
Skin biopsy demonstrating absent melanocytes in affected skin with no hyphae or spores within the stratum corneum.
Tinea corporis
SIGNS / SYMPTOMS
Inflammatory (red) annular plaques with leading-edge scale, central hypopigmentation, and folliculocentric pustules on any body surface.
Inflammatory lesions are often associated with pruritus.
No fluorescence with Wood lamp viewing.
INVESTIGATIONS
Septate hyphae with no yeast on KOH preparation.
Dermatophyte fungus (usually Trichophyton rubrum) on Sabouraud mycological media.
Skin biopsy demonstrates septate hyphae, with no yeast, in the stratum corneum, and frequently reveals an inflammatory infiltrate.
Seborrhoeic dermatitis
SIGNS / SYMPTOMS
Often associated with PV and occurs in similar distribution on the trunk, especially in men. However, seborrhoeic dermatitis is also often present on the scalp, face, ear canals, groin, and gluteal crease.
Erythema and pruritus common.
No associated pigmentary abnormalities.
No fluorescence on Wood lamp viewing. Seborrhoeic dermatitis can be seen in all age groups.
INVESTIGATIONS
Microscopy: yeast may be present on KOH preparation. However, associated hyphal forms are absent.
Skin biopsy does not demonstrate the characteristic short hyphae and budding yeast of PV, and instead often reveals pronounced epidermal spongiosis, acanthosis, and an inflammatory infiltrate.
Pityriasis rosea
SIGNS / SYMPTOMS
Similar scale to PV but no associated hypopigmentation. Erythematous discrete macules, often pruritic, on the entire trunk with a ‘Christmas tree’ pattern (individual lesions run parallel to the lines of skin cleavage). Begins with a solitary 'herald patch' before abrupt onset of eruption and resolves over 3 to 8 weeks with no chronicity or recurrence.
No fluorescence with Wood lamp viewing.
INVESTIGATIONS
Microscopy: negative with KOH preparation.
Skin biopsy does not demonstrate fungal forms and instead reveals epidermal acanthosis, spongiosis, mounding parakeratosis, and lymphocytic inflammation.
Pityriasis alba
SIGNS / SYMPTOMS
Frequently seen on the faces and arms of children with underlying atopic dermatitis.
No yellow fluorescence with Wood lamp viewing.
INVESTIGATIONS
Microscopy: negative with KOH preparation.
Skin biopsy does not demonstrate fungal forms and instead reveals mild epidermal spongiosis, and hyper- and parakeratosis with absent to mild lymphocytic inflammation.
Erythrasma
SIGNS / SYMPTOMS
Sharply demarcated brown scaly patches localised to intertriginous areas of the axillae, genitocrural crease, and web spaces of the toes.
Wood lamp examination, the optimal diagnostic tool, demonstrates coral red fluorescence instead of the yellow seen in PV.
INVESTIGATIONS
Microscopy: negative with KOH preparation.
Skin biopsy does not demonstrate fungal forms and instead reveals gram-positive coccobacilli (often appear filamentous on haematoxylin-eosin-, periodic acid-Schiff-, or Giemsa-stained sections) in the stratum corneum.
Confluent and reticulated papillomatosis of Gougerot and Carteaud
SIGNS / SYMPTOMS
Faintly erythematous to hyperpigmented, slightly scaly macules and patches in the intermammary and upper trunk similar to PV. However, no hypopigmentation. Confluent lesions on the central chest with reticulated peripheral borders.
No fluorescence with Wood lamp viewing.
INVESTIGATIONS
Microscopy with KOH preparation often reveals budding yeast with no hyphae (no spaghetti-and-meatballs appearance).
Skin biopsy demonstrates mild hyperkeratosis and papillomatosis limited to the valleys between elongated papillae. Yeast often present but no hyphae.
Melasma
SIGNS / SYMPTOMS
Hyperpigmented patches with no overlying scale on the face of young women.
No fluorescence with Wood lamp viewing.
INVESTIGATIONS
Microscopy: negative with KOH preparation.
Skin biopsy rarely needed.
Secondary syphilis
SIGNS / SYMPTOMS
Variety of presentations. Often presents with sharply demarcated, erythematous papules with overlying scale on the trunk, face, groin, and extremities with characteristic involvement of palms and soles. Mucous membrane lesions and generalised lymphadenopathy often present.
Negative Wood lamp examination.
INVESTIGATIONS
Microscopy: negative with KOH preparation.
Positive non-treponemal and treponemal serological testing.
Skin biopsy demonstrates psoriasiform epidermal hyperplasia with a band-like and perivascular plasma cell-rich infiltrate. Spirochetes on silver-stained sections with no fungal forms on periodic acid-Schiff- or Grocott-Gomori methenamine silver-stained sections.
Pinta
SIGNS / SYMPTOMS
Eruption begins with erythematous plaque with satellite papules that eventually become hyperpigmented and heal with depigmented macules primarily on the face, waistline, wrist flexures, and trochanteric region.[33]
Seen only in areas of the Brazilian rain forest.
Negative Wood lamp examination.
INVESTIGATIONS
Microscopy: negative with KOH preparation.
Darkfield microscopy examination of lesions shows spirochetes.
Leprosy (lepromatous)
SIGNS / SYMPTOMS
Disseminated ill-defined hypopigmented macules and patches. Early lepromatous disease is often not associated with loss of sensation. However, with time a symmetric bilateral peripheral neuropathy will develop. Lesions may be infiltrated and will not have scale.[34]
No fluorescence with Wood lamp viewing.
INVESTIGATIONS
Microscopy: negative with KOH preparation.
Skin biopsy demonstrating granulomatous dermatitis with numerous mycobacterial organisms on Fite stained sections.
Use of this content is subject to our disclaimer