Derm ◑87% 1 / 3 · unit 6 of 6
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Clinical features of plaque psoriasis

Topic 70 of 72 ✓textbook

Plaque psoriasis is the common kind — thick, silvery, scaly red patches on normal skin, because skin cells are being made far too fast.

Normally skin sheds over 14–20 days; in psoriasis that drops to just 3–4 days, so cells pile up into scaly plaques. They show up on the elbows, knees, and scalp, and anywhere skin is injured (the Koebner phenomenon), and often pit or lift the nails.

Underneath it's an immune-driven disease (the IL-17 / IL-23 pathway), which is why the newer 'biologic' drugs aim straight at those signals. It usually starts by age 40.

Plaque psoriasis (psoriasis vulgaris) is the most common form — a sharply bordered, silver-scaled red plaque ringed by normal-looking skin. It is driven by runaway epidermal turnover: shedding time collapses to 3–4 days from the normal 14–20 days.

The lesion:

  • A thick, sharply outlined plaque — silvery scale sitting over reddened skin, with clear skin around it;
  • The poorly-knit keratin is what looks silvery; dilated, VEGF-driven capillaries redden it;
  • Pruritus is common in moderate-to-severe disease or during a flare.

Where it appears:

  • Elbows, knees, and scalp, the face, and any spot of skin injury — new plaques at trauma sites are the Koebner phenomenon;
  • Nails — pitting, onycholysis, subungual hyperkeratosis, and dystrophy (in all subtypes; linked to psoriatic arthritis).

Underneath, it is a chronic, relapsing immune-driven disease running on the T-helper 17 pathway (IL-17, IL-23, TNF-α) — exactly what the newer biologic drugs target. It usually sets in by age 40.

Sources for this card

  • ✓Textbook McCance & Huether Ch. 46 — Psoriasis

    Plaque (psoriasis vulgaris) is the most common variant: well-demarcated silvery scaly erythematous plaques on normal skin; epidermal shedding falls to 3–4 days from the normal 14–20. Scalp/elbows/knees/trauma sites (Koebner); nail pitting. Th17 (IL-17/IL-23/TNF-α) mechanism.

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Diagnosis of rosacea

Topic 71 of 72 ◐textbook

Rosacea is diagnosed by how it looks — the book describes the appearance but gives no test or criteria.

The picture: lasting redness across the central face (forehead, nose, cheeks, chin) with tiny visible vessels, bumps and pustules, and easy flushing or burning. It's most common in fair-skinned, middle-aged women; sun, heat, alcohol, hot drinks, and stress set it off.

Watch for two extras: rhinophyma, a permanent bulbous thickening of the nose, and eye involvement (conjunctivitis, keratitis) that can happen even without any skin changes.

The textbook describes rosacea's appearance in detail but never states how it is diagnosed — no criteria, no workup. In practice rosacea is a clinical, by-appearance diagnosis; this card gives the features that carry that recognition and flags that the book supplies no formal method.

The recognisable picture — the central face (forehead, nose, cheeks, chin):

  • Persistent erythema, telangiectasia, papules and pustules;
  • Flushing, burning, and sun sensitivity from inappropriate vasodilation;
  • Middle-aged adults, more often women and fair skin;
  • Triggers — sun, heat, alcohol or hot drinks, hormonal change, stress; associated with Demodex folliculorum.

Four subtypes (alone or combined):

  • Erythematotelangiectatic; papulopustular;
  • Phymatous (nodular) — including rhinophyma, an irreversible bulbous nose from sebaceous hypertrophy, fibrosis, and telangiectasia;
  • Ocular — conjunctivitis and keratitis that can impair vision, and can occur independently of the skin findings.

Sources for this card

  • ✓Textbook McCance & Huether Ch. 46 — Rosacea

    Chronic central-face inflammation in fair-skinned, middle-aged women: erythema, telangiectasia, papules/pustules, flushing/burning. Four subtypes (erythematotelangiectatic, papulopustular, phymatous/rhinophyma [irreversible], ocular — can occur independently). No diagnostic criteria given.

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Factors that determine the prognosis of melanoma

Topic 72 of 72 ✓textbook

Melanoma's outlook depends mostly on how deep it is and how far it has spread.

The factors: tumour thickness (depth), how fast the cells are dividing (mitotic index), whether the surface is ulcerated, and whether it has reached lymph nodes or organs. Thickness leads the list and sets the stage.

Three numbers people mix up:

NumberWhat it means
2 mm or lessStage I (no spread)
Over 2 mmStage II (no spread)
Over 1 mm deepDo a sentinel-node biopsy

Once lymph nodes are involved it's Stage III; distant spread is Stage IV. Warning signs are ABCDE — Asymmetry, Border irregularity, Colour variation, Diameter over 6 mm, and Evolving/Elevation. Lesions on the arms and legs have the best surgical outlook, and catching it early raises survival.

Prognosis tracks how deep the melanoma is and how far it has spread. The factors are tumour thickness (depth), mitotic index, ulceration, and metastasis (lymph nodes/viscera), plus immunohistochemistry. Thickness leads the list and drives staging — the book stops short of naming any one factor 'most important.'

The prognostic factors (Ch. 46):

  • Thickness / depth of the lesion;
  • Mitotic index;
  • Ulceration;
  • Metastasis — number of lymph nodes or viscera involved;
  • Immunohistochemical assessment.

TNM staging — three thresholds not to confuse:

FindingStage
Lesion ≤ 2 mm, no nodes or distant spreadStage I
Lesion > 2 mm, no nodes or distant spreadStage II
Any size with positive lymph nodesStage III
Any size with distant metastasesStage IV

A sentinel-node biopsy is warranted once a lesion is > 1 mm deep (a distinct number from the 2 mm staging cutoff). Warning signs are ABCDE — Asymmetry, Border irregularity, Colour variation, Diameter > 6 mm, and Elevation/Evolving. Extremity lesions have the best surgical prognosis, and finding melanoma early raises 5-year survival.

Sources for this card

  • ✓Textbook McCance & Huether Ch. 46 — Malignant Melanoma (staging & prognosis)

    Prognostic factors: thickness/depth, mitotic index, immunohistochemistry, ulceration, metastasis (nodes/viscera). TNM: Stage I ≤2 mm, II >2 mm (no spread), III positive nodes, IV distant mets; sentinel-node biopsy if >1 mm deep. Extremity lesions best prognosis; the book names no single 'most important' factor.

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