Can tinea corporis (ringworm of the body) resemble psoriasis vulgaris or pityriasis rubra pilaris (PRP) histopathologically?

Histopathologic Resemblance of Tinea Corporis to Psoriasis and Pityriasis Rubra Pilaris

Yes, tinea corporis can histopathologically resemble both psoriasis vulgaris and pityriasis rubra pilaris, making clinical-pathological correlation essential for accurate diagnosis.

Key Histopathologic Overlaps

Tinea Corporis vs. Psoriasis Vulgaris

Tinea corporis can share several histologic features with psoriasis, creating diagnostic confusion:

• Psoriasiform hyperplasia with elongated rete ridges can occur in both conditions 1
• Parakeratosis (abnormal retention of nuclei in the stratum corneum) may be present in both entities 1
• Neutrophil collections in the stratum corneum can appear in tinea corporis, mimicking the neutrophilic mounds characteristic of psoriasis 2

However, fully developed psoriasis typically shows thin rete ridges, thin suprapapillary plates, broad dermal papillae, and neutrophils in mounds of parakeratosis, whereas these features may be less organized or absent in tinea corporis 1.

Tinea Corporis vs. Pityriasis Rubra Pilaris

The clinical and histopathologic overlap between tinea corporis and PRP is well-documented:

• A 61-year-old patient initially diagnosed with extensive tinea corporis was ultimately found to have PRP after failing multiple antifungal treatments and developing progressive disease 3
• The initial presentation of PRP can manifest as ring-like lesions that clinically mimic tinea corporis 3
• PRP shows alternating orthokeratosis and parakeratosis in both vertical and horizontal directions, focal hypergranulosis, thick suprapapillary plates, and broad rete ridges—features that can overlap with inflammatory dermatophyte infections 1

Critical Diagnostic Approach

When Histopathology Shows Psoriasiform Changes

Always obtain fungal culture and/or PAS staining to exclude dermatophyte infection when encountering psoriasiform hyperplasia histologically 4. The presence of fungal hyphae definitively establishes tinea corporis.

Clinical-Pathological Correlation is Mandatory

• Tinea corporis typically presents as annular, expanding plaques with central clearing and an active, scaly border—distinct from the well-demarcated, silvery-scaled plaques of psoriasis 4
• PRP characteristically shows follicular hyperkeratosis, palmoplantar keratoderma, and "islands of sparing" within erythematous areas—features absent in typical tinea corporis 3, 1
• Poor response to appropriate antifungal therapy should prompt reconsideration of the diagnosis and consideration of repeat biopsy 3

Specific Histologic Discriminators

Psoriasis vulgaris demonstrates:

• Neutrophils organized in mounds of parakeratosis (Munro microabscesses) 1
• Thin suprapapillary plates with dilated, tortuous capillaries 1
• Uniform thinning of rete ridges 1

PRP shows:

• Alternating orthokeratosis and parakeratosis in checkerboard pattern 1
• Follicular plugging (when follicular lesions are biopsied) 1
• Thick suprapapillary plates and broad rete ridges 1

Tinea corporis requires:

• Demonstration of fungal elements on PAS or GMS staining for definitive diagnosis 4
• Fungal culture confirmation of dermatophyte species 5

Common Diagnostic Pitfalls

• Never rely on histopathology alone when psoriasiform hyperplasia is present—always correlate with clinical presentation and consider fungal studies 3, 4
• Initial biopsies may be non-diagnostic or misleading in evolving inflammatory conditions; repeat biopsy may be necessary if clinical course is atypical 3
• Failure to respond to appropriate therapy (antifungals for presumed tinea, topical steroids for presumed psoriasis) mandates diagnostic reassessment 3
• Multiple biopsies from different sites enhance diagnostic accuracy when the diagnosis remains uncertain 2