Carpet Tack Sign
The Carpet Tack sign (also known as the “tack sign” or “cat’s tongue sign”) is a clinical finding associated with Discoid Lupus Erythematosus (DLE), a chronic cutaneous form of lupus.
Clinical Significance
- The Finding: When a adherent, hyperkeratotic scale is gently pulled or lifted from a DLE lesion, the undersurface of the scale reveals small, horn-like keratinous spikes that look like the underside of a carpet tack.
- Etiology: These spikes correspond to the dilated, keratotic follicular orifices that penetrate deep into the hair follicles.
Context in Lupus Erythematosus
| Feature | Details |
|---|---|
| Disease | Discoid Lupus Erythematosus (DLE). |
| Lesion Type | Erythematous, indurated plaques with central atrophy, scaling, and follicular plugging. |
High-Yield Exam Pearl:
- Follicular Plugging: The carpet tack sign is essentially a physical manifestation of severe follicular plugging.
- Diagnostic Utility: While classic for DLE, it is not seen in all cases, but its presence is highly specific and points strongly toward a diagnosis of chronic cutaneous lupus over other inflammatory conditions like psoriasis or seborrheic dermatitis.