Papulosquamous Disorders
Papulosquamous disorders are a group of conditions characterized by papules and plaques with surface scale. Distinguishing between them relies on distribution, scale characteristics, and associated systemic symptoms.
Key Differentials
| Condition | Key Clinical Features |
|---|---|
| Psoriasis | Well-demarcated plaques, silvery scale, extensor surfaces. |
| Pityriasis Rosea | “Herald patch,” followed by Christmas-tree distribution. |
| Lichen Planus | Violaceous, flat-topped papules (6 Ps); Wickham striae. |
| Secondary Syphilis | Red-brown papules on palms and soles. |
Diagnostic Pearls
- Auspitz Sign: Pinpoint bleeding upon removal of a scale, characteristic of psoriasis.
- Herald Patch: A solitary, larger, oval-shaped patch that precedes the diffuse rash in Pityriasis Rosea.
- Distribution: Always assess for mucosal involvement (Lichen Planus) and palm/sole involvement (Secondary Syphilis).
High-Yield Exam Pearl:
- Psoriasis Management: Always be cautious with systemic steroids; they can precipitate pustular psoriasis upon withdrawal.
- Differential Diagnosis: If a patient presents with a “psoriasis-like” rash that is resistant to treatment, biopsy is necessary to rule out Cutaneous T-cell Lymphoma (Mycosis Fungoides).