Skin Itch (pruritus)
Pruritus is an unpleasant cutaneous sensation that provokes the desire to scratch, arising from dermatological, systemic, neurogenic, or psychogenic causes.
Murtagh Diagnostic Strategy
| Category | Diagnosis | Key Discriminator | Cantonese Question / Finding |
|---|---|---|---|
| Probability Diagnosis | Atopic dermatitis (eczema) [3][7] | Chronic relapsing itch, flexural distribution, personal/family atopy | 「你細個有冇濕疹？手踭膝頭窩有冇紅疹？」 |
| Contact dermatitis [7] | Localised to area of exposure, temporal link to irritant/allergen | 「有冇接觸新嘅嘢之後先開始痕？」 | |
| Urticaria [12] | Wheals (風癩) that come and go within 24h, individual lesion < 24h | 「啲紅疹係咪一嚿嚿凸起、幾個鐘頭後自己消？」 | |
| Tinea (fungal) [6] | Annular scaly plaque with central clearing; asymmetric | 「係咪圓形、中間好啲、邊緣紅同甩皮？」 | |
| Xerosis / Dry skin | Elderly, winter, low humidity, no primary rash | 「皮膚有冇好乾、爆裂？冬天特別差？」 | |
| Serious Not To Miss | Lymphoma (Hodgkin's) [4] | Generalised itch without rash + B-symptoms + lymphadenopathy | 「有冇消瘦、夜晚出汗、頸或腋下腫？」 |
| Chronic liver disease / PBC [8] | Jaundice, cholestatic LFT, xanthomata, middle-aged female | 「有冇眼黃？皮膚有冇黃色粒粒（膽固醇沉積）？」 | |
| CKD / Uraemic pruritus [9] | Known CKD or raised creatinine, nocturia, fatigue | 「有冇腎病紀錄？夜晚起身去幾多次廁所？」 | |
| Polycythaemia vera [4] | Aquagenic pruritus after hot bath, facial plethora, splenomegaly | 「沖完涼之後特別痕？面有冇紅啲？」 | |
| Pitfalls | Scabies [6] | Intense itch worse at night, finger webs/wrists/groin, household contacts | 「屋企人有冇一齊痕？手指罅有冇粒粒？」 |
| Psoriasis [6] | Well-demarcated silvery-scaled plaques on extensors, mild itch | 「有冇邊界好清楚、銀色皮屑嘅紅疹喺手踭膝頭？」 | |
| Bullous pemphigoid [13] | Elderly, tense blisters on erythematous base, severe itch | 「皮膚有冇起大水泡？底部紅唔紅？」 | |
| Masquerades | Drug-induced pruritus [5] | Temporal relation to new drug; resolves on withdrawal | 「新藥食咗幾耐先開始痕？」 |
| Diabetes mellitus [11] | Pruritus vulvae/generalised; polyuria, polydipsia | 「有冇口渴、去廁所多、體重跌？」 | |
| Thyroid disease [10] | Hyperthyroid: warm moist skin, tremor; Hypothyroid: dry skin | 「有冇怕熱、手震、心跳快？定係怕凍、皮膚好乾？」 | |
| Iron deficiency anaemia | Generalised itch without rash, pallor, fatigue | 「有冇面青、容易攰、頭暈？」 | |
| Stress / Anxiety / Depression | Life stressors, sleep, mood, relationship | 「最近有冇咩令你壓力特別大？心情點？」 | |
| Fear of cancer / serious illness | Health anxiety triggered by reading online | 「你有冇擔心呢個痕係嚴重嘅病？」 |
| Time | Task | Cantonese Key Phrases | Why It Scores Marks |
|---|---|---|---|
| 0:00–0:30 | Greeting, introduction, rapport | 「你好，我係XX醫生，今日想同你傾下你嘅問題，可以嗎？」(Hello, I'm Dr XX, I'd like to chat about your problem today, is that OK?) | Friendly opening, permission → interpersonal marks |
| 0:30–2:00 | HPI: onset, duration, site, character, severity, aggravating/relieving, progression, associated rash | 「你幾時開始痕㗎？」「邊度最痕？」「有冇紅疹、粒粒、水泡？」「有冇嘢令到佢痕啲或者好啲？」「瞓覺有冇影響到？」 | Structured symptom analysis; severity + sleep disturbance = functional impact marks |
| 2:00–3:00 | Red flags & systemic review: weight loss, jaundice, bleeding, lymph nodes, night sweats, new drugs | 「有冇消瘦、眼黃、周身淋巴腫大、夜晚出汗？」「最近有冇食新嘅藥？」 | Rules out serious/systemic causes (lymphoma, CKD, liver disease, drug reaction) |
| 3:00–3:45 | PMH, Drug Hx, Allergy, FHx, Social Hx | 「你有冇長期病？」「食緊咩藥？」「有冇敏感史？」「屋企人有冇濕疹、鼻敏感、哮喘？」「你做咩工作㗎？屋企有冇養寵物？」 | Atopy FHx, occupational/contact exposures, drug causes |
| 3:45–4:30 | ICE: Ideas, Concerns, Expectations | 「你自己覺得痕嘅原因係咩呢？」(Ideas)「你最擔心啲咩？」(Concerns)「你今日嚟想我幫你做啲咩？」(Expectations) | Directly scores ICE marks; uncovers hidden agenda |
| 4:30–5:15 | Signpost → Focused physical exam offer | 「我想睇下你塊皮膚，可以嗎？」 | Shows clinical competence; identifies supporting physical sign |
| 5:15–5:45 | Summarise back | 「等我總結返：你痕咗X個星期，主要喺XX位，仲有XX。你擔心係XX，想我幫你搵下原因同舒緩返。啱唔啱？」 | Summarising + checking understanding = high interpersonal marks |
| 5:45–6:00 | Closing & safety net | 「我會幫你安排檢查，如果之後痕得更犀利、有發燒、體重急跌，記得即刻返嚟。」 | Safe closure, safety-net advice |
Uncovering the hidden agenda: The patient may present with "itchy skin" but the real reason for consultation (RFC) could be fear of cancer (lymphoma), stress-related itch, concern about a new medication, or cosmetic/social embarrassment. Always ask: 「你最擔心啲咩？點解揀今日嚟睇醫生？」
| Domain | English Question | Cantonese Question | Why It Matters | If Positive, Think Of |
|---|---|---|---|---|
| Onset/Duration | When did itching start? Acute vs chronic? | 「幾時開始痕？痕咗幾耐？」 | Acute < 6 wks (contact, urticaria, drug, scabies); Chronic > 6 wks (eczema, systemic) | Acute → drug reaction, urticaria; Chronic → eczema, psoriasis, systemic |
| Site/Distribution | Where is the itch? Localised or generalised? | 「邊度痕？淨係一個位定全身都痕？」 | Localised → primary skin disease; Generalised without rash → systemic cause [1] | Flexures → eczema; Extensors → psoriasis; Webs of fingers → scabies; Generalised → systemic |
| Rash present? | Is there a rash, bumps, blisters, or scaling? | 「有冇出紅疹、粒粒、水泡、甩皮？」 | Itch with rash → dermatological; Itch without rash → systemic pruritus [1][2] | No rash: CKD, liver, thyroid, lymphoma, polycythaemia vera, drug |
| Severity/Sleep | Does the itch affect sleep or daily life? | 「痕到瞓唔到覺？影唔影響返工返學？」 | Functional impact → biopsychosocial; sleep disturbance → severity marker | Eczema worse at night [3]; scabies worse at night (mite active) |
| Aggravating factors | Worse with heat, water, sweat, detergents, certain foods? | 「沖涼之後痕唔痕啲？出汗、天氣轉有冇影響？」 | Aquagenic pruritus (itch after water contact) → polycythaemia vera [4] | Hot bath → PV; Sweat/heat → cholinergic urticaria; Detergent → contact dermatitis |
| New exposures | New soaps, cosmetics, jewellery, plants, occupational chemicals? | 「最近有冇用新嘅清潔劑、護膚品、飾物？」 | Contact dermatitis (allergic or irritant) | Patch test if suspected contact allergy |
| Medications | Any new drugs started? (antibiotics, NSAIDs, ACEi, statins, opioids) | 「最近有冇食新藥？例如止痛藥、抗生素、血壓藥？」 | Drug-induced pruritus is a common masquerade [1] | ACEi, opioids, antibiotics, antithyroid drugs → pruritus ± rash [5] |
| Close contacts | Anyone at home also itchy? | 「屋企人有冇一齊痕？」 | Household contacts itchy → scabies [6] | Scabies: contact tracing + simultaneous treatment |
| Atopy FHx | Do you or family have eczema, asthma, hay fever? | 「你或屋企人有冇濕疹、鼻敏感、哮喘？」 | Personal/Family history of atopy = key diagnostic criterion for atopic dermatitis [3][7] | Atopic dermatitis |
| Weight loss/Night sweats | Any unexplained weight loss, night sweats, swollen glands? | 「有冇唔明原因消瘦、夜晚出汗、頸或腋下腫脹？」 | B-symptoms → lymphoma (Hodgkin's) | Lymphoma: urgent referral |
| Jaundice/Dark urine | Any yellowing of eyes, dark urine, pale stool? | 「有冇眼黃、茶色尿、白色大便？」 | Cholestatic pruritus: PBC, obstructive jaundice [8] | PBC, biliary obstruction |
| Renal history | Any kidney problems? Foamy urine? | 「有冇腎病？小便有冇好多泡？」 | Uraemic pruritus in CKD [9] | CKD stage 4-5 |
| Thyroid symptoms | Any heat intolerance, weight change, tremor? | 「有冇怕熱、心跳快、手震、體重變化？」 | Hyperthyroidism → pruritus and urticaria; Hypothyroidism → dry skin/itch [10] | Thyroid disease |
| DM symptoms | Any increased thirst, urination? | 「有冇口渴多咗、去廁所多咗？」 | DM → pruritus vulvae/generalised itch (fungal, neuropathic) [11] | Diabetes mellitus |
| Psych/Stress | Under any stress? Mood? Scratching habit? | 「最近壓力大唔大？心情點？有冇不自覺咁搲？」 | Psychogenic pruritus; stress exacerbates eczema | Stress, depression, dermatitis artefacta |
| Sexual/Genital | Any genital itch specifically? | 「有冇特別下體痕？」 | Candidiasis (DM), STI, pubic lice, scabies | Candida, dermatophyte, scabies |
| Occupation | What do you do for work? | 「你做咩嘢工㗎？」 | Occupational contact dermatitis (hairdresser, cleaner, healthcare) | Irritant/allergic contact dermatitis |
Case Report Form Answer Builder
- CC: "Skin itch for __ weeks/months"
- HPI points to capture: Onset & duration; site & distribution (localised vs generalised); presence/absence of rash; character (constant vs intermittent); severity (sleep disturbance, work impact); aggravating factors (heat, water, detergents, specific allergens); relieving factors (moisturiser, antihistamines); associated symptoms (rash morphology, scaling, vesicles, weeping); temporal relation to new drugs/exposures; systemic symptoms screened (weight loss, jaundice, polyuria, night sweats, lymphadenopathy); previous treatment tried.
- Examples: "Persistent itch not responding to over-the-counter cream"; "Worried the itch might be a sign of serious disease"; "Itch affecting sleep and work performance"; "Family member told patient to see doctor because itch spreading."
- How to phrase: State the trigger that brought the patient TODAY, not just the symptom. E.g., "Patient presents due to worsening nocturnal pruritus causing insomnia for 2 weeks, prompting concern about underlying cause."
| Component | Likely Examples | Wording for CRF |
|---|---|---|
| Ideas | "I think it might be eczema / allergy / fungal infection" | "Patient thinks the itch is due to allergy/eczema" |
| Concerns | "I'm worried it could be cancer / kidney problem / contagious" | "Patient is concerned the itch may indicate a serious internal disease" |
| Expectations | "I want a blood test / cream / referral to dermatologist" | "Patient expects investigation to exclude systemic cause and treatment to relieve itch" |
- In a young-to-middle-aged patient with flexural itch + rash + atopy history → Atopic dermatitis (eczema) [3][7]
- Minimum supporting evidence: Chronic/relapsing pruritus, ill-defined erythematous patches on flexural surfaces, personal or family history of atopy (eczema/asthma/allergic rhinitis), dry skin (xerosis).
- If elderly + generalised itch WITHOUT rash → consider systemic causes (CKD, liver, lymphoma, drug).
- If clear contact history → Contact dermatitis.
| DDx | Key Discriminator |
|---|---|
| Contact dermatitis | Localised distribution matching area of exposure; temporal link to irritant/allergen |
| Scabies | Intense nocturnal itch, finger-web burrows, household contacts affected |
| Urticaria | Transient wheals (< 24h each), raised, blanching, often associated with angioedema |
(Adjust based on stem: if elderly + no rash, substitute with CKD/uraemic pruritus, PBC, lymphoma.)
| Domain | Problem |
|---|---|
| Biological | Chronic pruritic dermatitis causing skin excoriation and risk of secondary infection |
| Psychological | Sleep disturbance and anxiety/frustration due to persistent itch; worry about serious underlying cause |
| Social | Impact on work productivity / social embarrassment due to visible scratch marks or rash; need for household contact treatment if scabies |
| Diagnosis/DDx | Best Supporting Physical Sign | How to Elicit | Why It Supports This Diagnosis |
|---|---|---|---|
| Atopic dermatitis (most likely) | Ill-defined erythematous, excoriated patches with lichenification on flexural surfaces (antecubital/popliteal fossae) [3] | Inspect flexural surfaces with adequate exposure; look for lichenification, xerosis, excoriation marks | Flexural lichenification with ill-defined borders is the hallmark of chronic atopic dermatitis in adults |
| Contact dermatitis | Localised eczematous patch corresponding to area of exposure (e.g., watch strap, waistband) | Inspect area of suspected contact; note sharp demarcation matching object shape | Distribution matching the contactant is pathognomonic |
| Scabies | Burrows in finger webs, wrist flexor, or genital area [6] | Inspect finger webs, wrists, axillae, groin with magnification; use dermoscopy if available for "delta-wing jet" sign | Burrows are pathognomonic for scabies |
| Urticaria | Transient raised wheals that blanch on pressure | Press a wheal with glass slide (diascopy); individual lesion resolves < 24h | Wheals that appear and disappear within hours are diagnostic of urticaria |
| Psoriasis | Well-demarcated erythematous plaque with silvery scale on extensor surfaces; Auspitz sign [6] | Gently remove scale → pinpoint bleeding (Auspitz sign) | Well-demarcated silver scale differentiates from ill-defined eczema |
| Systemic (CKD, liver, lymphoma) | No primary rash; only excoriation marks (secondary lesions) ± pallor, jaundice, lymphadenopathy, splenomegaly | General inspection, conjunctival pallor, scleral icterus, palpate cervical/axillary nodes, palpate spleen | Generalised pruritus without primary skin lesion = red flag for systemic cause [1][2] |
Top Traps That Lose Marks
- Forgetting to ask about rash presence — Itch WITHOUT rash = systemic cause until proven otherwise [1][2]. This is the single most important discriminator.
- Missing scabies — Always ask about household contacts and check finger webs. Scabies mimics eczema and is the classic "pitfall."
- Not asking about new medications — Drug-induced pruritus (opioids, ACEi, antibiotics, antithyroid drugs) is a common masquerade [5].
- Ignoring systemic red flags — Weight loss, night sweats, jaundice, polyuria → must screen for lymphoma, CKD, liver disease, DM, thyroid.
- Skipping ICE — The hidden agenda often IS the exam. Patient may fear cancer or be stressed at work. If you don't ask, you lose easy marks.
- Writing "allergy" as the diagnosis — Be specific: atopic dermatitis, allergic contact dermatitis, urticaria. "Allergy" is not a diagnosis.
- Confusing eczema and psoriasis — Eczema = ill-defined, flexural, intensely itchy; Psoriasis = well-demarcated, extensor, silvery scale, mildly itchy [6][7].
Must-Not-Miss Red Flags → Urgent Referral:
- Generalised pruritus without rash + weight loss + night sweats + lymphadenopathy → lymphoma → urgent haematology referral
- Jaundice + pruritus → obstructive biliary disease / PBC → urgent LFT, USG, hepatology referral
- Widespread blistering on erythematous base in elderly → bullous pemphigoid → dermatology referral
- Erythroderma (> 75% BSA erythema + scaling) → dermatological emergency → admit
Shortest Safe Management / Safety Net: 「我會開啲潤膚膏同止痕藥畀你先，同埋安排驗血排除內科原因。如果痕得更犀利、出現發燒、急速消瘦、或者皮膚起大範圍水泡，記得即刻返嚟或者去急症室。」
"I'll prescribe moisturiser and antihistamines first, and arrange blood tests to rule out internal causes. If the itch gets much worse, you develop fever, rapid weight loss, or widespread blistering, come back immediately or go to A&E."
High Yield Summary
What to ASK: Rash or no rash? (single most important question); site/distribution; severity/sleep impact; aggravating factors (water, heat, detergents); new drugs; household contacts itchy; atopy personal/family history; systemic red flags (weight loss, jaundice, polyuria, night sweats, lymphadenopathy); ICE + hidden agenda.
What to WRITE: CC with duration → structured HPI → RFC (why today?) → ICE → Most likely Dx with evidence → 3 DDx with discriminators → 3 biopsychosocial problems → 1 physical sign (flexural lichenification for eczema; excoriations only for systemic).
What NOT to MISS: Scabies (household contacts, finger webs); drug-induced pruritus; systemic pruritus without rash (CKD, liver, lymphoma, thyroid, DM, polycythaemia vera); hidden psychological agenda.
Active Recall - Family Medicine Clinical Test
[1] GC 085. Skin rash_Doctor I have a rash.pdf [2] Ryan Ho Fundamentals.pdf (Section 3.7.4.1 History Taking in Dermatology) [3] MBBS Final MB (Medicine) (Felix PY Lai).pdf (Atopic Dermatitis section, p.1786-1789) [4] Ryan Ho Haemtology.pdf (Polycythaemia Vera, p.76) [5] Endocrine Interactive Tutorial.pdf (Antithyroid drug side effects) [6] Maksim Medicine Notes.pdf (Dermatology, p.69-72) [7] GC 065. I have an itchy rash.pdf [8] Ryan Ho GI.pdf (PBC, p.284-288) [9] Block A - Chronic Kidney Disease and its Complications.pdf (p.6) [10] Ryan Ho Endocrine.pdf (Thyroid presenting problems, p.11) [11] Block A - Polyuria and polydipsia_ glucose metabolism; diabetes mellitus; diabetic ketoacidosis.pdf (p.2) [12] GC 093. Urticaria, angioedema and anaphylaxis.pdf [13] Block A - Dermatology PBL 2.pdf (Bullous pemphigoid, p.4)
Skin Injury
Skin injury is damage to the integumentary tissue caused by mechanical, thermal, chemical, or radiation forces, ranging from superficial abrasions to full-thickness wounds involving the epidermis, dermis, and underlying structures.
Skin Lesions (pigmented)
Pigmented skin lesions are areas of skin with altered coloration due to changes in melanin production, melanocyte proliferation, or vascular abnormalities, ranging from benign nevi and seborrheic keratoses to malignant melanoma.