Differential Diagnosis of Tinea

Clinical Presentation and Differential Diagnoses

The British Journal of Dermatology recommends considering seborrheic dermatitis, psoriasis, and atopic dermatitis in the differential diagnosis of tinea capitis, as they may present with similar symptoms 1
Kerion, an inflammatory variant of tinea capitis, is commonly misdiagnosed as a bacterial abscess, but may also resemble folliculitis or regional lymphadenopathy 1, 2
The black dot pattern of tinea capitis may be confused with trichotillomania or traction alopecia, highlighting the importance of laboratory confirmation 1
Favus, a variant of tinea capitis, can be mistaken for impetigo or severe seborrheic dermatitis, but is characterized by yellow crusted cup-shaped lesions 1
In immunocompromised patients, the differential diagnosis of tinea expands to include non-infectious mimics such as drug eruptions, cutaneous infiltration with underlying malignancy, and chemotherapy or radiation-induced reactions 3, 4
Infectious differentials in immunocompromised patients are broader and may include bacterial, fungal, viral, and parasitic infections 3, 4, 5

The British Journal of Dermatology suggests that laboratory confirmation is essential for the diagnosis of tinea, as clinical diagnosis can be unreliable 2
A KOH preparation showing hyphae or arthroconidia can provide rapid confirmation of tinea, while fungal culture on Sabouraud agar is the gold standard for species identification 2
In immunocompromised patients with atypical presentations, biopsy or aspiration may be necessary for diagnosis 3, 4

In immunocompromised hosts, the differential diagnosis expands to include cutaneous manifestations of disseminated fungal infections, such as Aspergillus, Mucor, Fusarium, and Scedosporium, which present as papules, nodules, or ulcers with potential for rapid progression, according to the Infectious Diseases Society of America 6, 7
Nocardia infections manifest as painless subcutaneous nodules or abscesses that are "cold to the touch," usually representing metastatic foci from pulmonary infection, as noted by the Infectious Diseases Society of America 6, 7

Wood's lamp examination can identify certain infections, such as M. canis, which shows green fluorescence, and favus, which shows fluorescence, although most common dermatophytes do not fluoresce, as reported by the British Association of Dermatologists 8, 9
Kerion, an inflammatory variant of tinea capitis, is frequently misdiagnosed as bacterial abscess, presenting as a painful, boggy mass with pustules and regional lymphadenopathy, but secondary bacterial infection should not be overlooked, according to the British Association of Dermatologists 8, 9, 10