How can you distinguish between ringworm and a subcutaneous tick? - briefly
Ringworm manifests as a circular, scaly, erythematous plaque with a raised, expanding border, while a subcutaneous tick forms a firm, often painless nodule that may contain a visible or palpable foreign body within the skin. Diagnosis depends on visual assessment of lesion shape and texture, with dermatoscopic examination confirming fungal hyphae or the tick’s body.
How can you distinguish between ringworm and a subcutaneous tick? - in detail
Ringworm and a subcutaneous tick present distinct clinical patterns that allow reliable differentiation.
The fungal infection typically appears as a circular, erythematous plaque with a raised, scaly border and a clearer centre. The margin may exhibit fine, peripheral scaling and occasional vesiculation. Lesions often occur on moist skin areas such as the groin, feet, or scalp, and may be pruritic. The organism resides in the stratum corneum, so the infection remains superficial and does not produce palpable nodules beneath the skin.
A subcutaneous tick, in contrast, manifests as a firm, tender nodule or swelling at the site of attachment. The lesion is usually non‑scaly, may exhibit a small punctum indicating the mouthparts, and can be accompanied by localized erythema or edema. Pain or a sensation of movement may be reported. The parasite embeds its body within the dermis and subcutaneous tissue, creating a deeper, often mobile mass.
Key distinguishing features include:
- Surface appearance: scaly, annular plaque (fungal) versus smooth, firm nodule (tick).
- Depth of involvement: epidermal surface (ringworm) versus dermal/subcutaneous layer (tick).
- Border characteristics: raised, scaling edge (fungus) versus well‑defined, non‑scaling margin (tick).
- Presence of punctum: absent in dermatophyte infection, often visible in tick attachment.
- Symptom profile: intense itching (fungus) versus localized pain or movement sensation (tick).
Diagnostic confirmation may involve:
- Skin scraping for potassium hydroxide preparation to reveal hyphae, confirming dermatophyte infection.
- Dermoscopy to visualize the tick’s body and legs within the lesion.
- Ultrasound to assess depth and detect a foreign body structure.
- Biopsy when atypical features arise, distinguishing fungal hyphae from inflammatory response to a parasite.
Treatment follows the identified condition: topical or oral antifungals for the fungal disease; surgical removal of the tick, often accompanied by antibiotics if secondary infection is suspected. Prompt identification prevents complications such as secondary bacterial infection in fungal cases or systemic disease transmission from the tick.