About This Page
This is a clinician-written, evidence-based guide aligned to the MCC Examination Objectives. It is structured by clinical presentation — the way the MCCQE tests and the way patients actually present. Management reflects current Canadian guidelines (CMA, CFPC, CPS). Always cross-reference with institutional protocols and clinical judgment.
The Bottom Line
- The first question is whether there are primary skin lesions; excoriations alone may be secondary to scratching
- Generalized itch without primary rash should trigger systemic review: cholestasis, kidney disease, iron deficiency, polycythaemia vera, lymphoma, thyroid disease, diabetes, pregnancy, and drugs
- Nocturnal itch, household contacts, burrows, interdigital involvement, or genital nodules suggests scabies even if the rash is subtle
- Treat the cause: emollients and topical anti-inflammatory therapy for eczema, permethrin/ivermectin for scabies, bile-acid or specialist therapies for cholestasis, and systemic-disease treatment when identified
- Red flags include weight loss, fever, night sweats, jaundice, renal symptoms, pregnancy, severe sleep disruption, older age with new generalized itch, and immunosuppression
Approach to the Presentation
Pruritus is a high-yield MCC presentation because it forces candidates to separate dermatologic itch from systemic disease. Begin by deciding whether the skin findings are primary or secondary. Primary lesions include eczema, urticaria, lichen planus, psoriasis, scabies, bites, vesicles, and bullae. Secondary lesions include excoriations, crusting, lichenification, and prurigo nodules caused by scratching. Then classify itch as localized or generalized, acute or chronic, and associated or not associated with systemic symptoms. A meticulous medication review, occupational history, travel/household exposure history, pregnancy history, and examination for jaundice, lymphadenopathy, hepatosplenomegaly, thyroid disease, renal disease, and infestation are central.
Differential Diagnosis
| diagnosis | likelihood | key features | distinguishing test |
|---|---|---|---|
| Cholestatic Liver Disease / Biliary Obstruction | must-not-miss | Generalized itch often worse at night, jaundice, dark urine, pale stools, right upper quadrant symptoms, pregnancy or liver disease risk | ALT/AST, alkaline phosphatase, bilirubin, GGT; abdominal ultrasound if cholestatic pattern |
| Chronic Kidney Disease / Uremic Pruritus | must-not-miss | Generalized itch in CKD or dialysis; xerosis common; restless sleep; excoriations without a primary rash | Creatinine/eGFR, electrolytes, urinalysis, albuminuria assessment |
| Haematologic Disease (Lymphoma, Polycythaemia Vera, Iron Deficiency) | must-not-miss | Aquagenic itch, pruritus after bathing, B symptoms, lymphadenopathy, splenomegaly, fatigue, pallor, thrombosis history | CBC with differential, ferritin, peripheral smear; further haematology testing if abnormal |
| Scabies / Pediculosis | must-not-miss | Severe nocturnal itch, household or institutional spread, burrows, interdigital wrists/waist/genitals, nodules on scrotum; crusted scabies in immunocompromised | Clinical diagnosis; dermoscopy or skin scraping if available. Treat contacts simultaneously |
| Xerosis / Asteatotic Eczema | common | Dry cracked itchy skin, worse in winter, older age, frequent washing, low humidity; lower legs and trunk commonly affected | Clinical diagnosis; improvement with emollients and irritant avoidance |
| Atopic Dermatitis | common | Chronic relapsing itch, flexural eczema, personal/family atopy, lichenification, sleep disturbance | Clinical diagnosis; assess severity, infection, and triggers |
| Allergic or Irritant Contact Dermatitis | common | Localized itch and eczema corresponding to exposure: hands, face, eyelids, jewellery, adhesives, gloves, cosmetics, occupational substances | Exposure history; patch testing for recurrent allergic cases |
| Urticaria | common | Transient wheals lasting less than 24 hours, intensely itchy, may have angioedema; physical or spontaneous triggers | Clinical diagnosis; limited testing unless chronic, systemic, or atypical |
| Drug-Induced Pruritus | common | Temporal association with opioids, antibiotics, antimalarials, hydroxychloroquine, statins, ACE inhibitors, biologics, or cholestatic drug injury | Medication timeline, liver/renal tests if generalized or systemic symptoms |
| Thyroid Disease / Diabetes Mellitus | less common | Hyperthyroid sweating/weight loss/tremor or hypothyroid dry skin/cold intolerance; diabetes-associated xerosis or candidiasis | TSH, glucose or A1c when clinically indicated |
| Psychogenic or Neuropathic Pruritus | less common | Localized itch in a nerve distribution or chronic itch with psychiatric comorbidity after exclusion of primary skin/systemic disease | Diagnosis of exclusion; neurological exam and targeted assessment |
Red Flags & Key History
Symptoms
Generalized itch without primary rash, especially in older adult — systemic cause must be considered
Fever, night sweats, weight loss, lymph node swelling — lymphoma or systemic inflammatory disease
Jaundice, dark urine, pale stool, right upper quadrant pain, pregnancy — cholestasis
Aquagenic pruritus after bathing — polycythaemia vera is a classic association
Severe nocturnal itch affecting household contacts — scabies or infestation
New medication, dose change, or supplement use before itch began
Occupational wet work, glove use, chemicals, cosmetics, fragrances, adhesives, hair dyes, or nickel exposure
Dryness worse in winter or after frequent bathing — xerosis/asteatotic eczema
Signs
Jaundice, hepatomegaly, scratch marks without primary rash
Lymphadenopathy or splenomegaly
Burrows in finger webs, wrists, belt line, nipples, or genitals
Excoriations only, without primary lesions — consider systemic or neuropathic itch
Lichenification and flexural eczema — chronic atopic dermatitis
Transient wheals or dermatographism — urticaria
Approach to Investigation
First-line
Full skin examinationLook for primary lesions, burrows, wheals, scale, plaques, vesicles, bullae, lichen planus, psoriasis, lice/nits, and excoriation-only patterns
CBC with differential and ferritinScreens for anaemia, iron deficiency, eosinophilia, polycythaemia, leukocytosis, or haematologic clues
Creatinine/eGFR, electrolytes, urinalysisAssesses CKD and renal causes of generalized pruritus
Liver enzymes, alkaline phosphatase, bilirubinEssential when itch is generalized, nocturnal, associated with jaundice, pregnancy, or medication-related cholestasis
Second-line
TSH and glucose/A1cUse when symptoms suggest thyroid disease or diabetes, or when generalized itch remains unexplained
Scabies scraping or dermoscopyHelpful if diagnosis uncertain, but treatment should not be withheld when clinical suspicion is high
Chest imaging or additional malignancy workupConsider if B symptoms, lymphadenopathy, abnormal CBC, smoking history, or persistent unexplained generalized pruritus
Specialist
Dermatology referralFor refractory itch, diagnostic uncertainty, suspected blistering disease, severe eczema/psoriasis, lichen planus, or need for phototherapy/systemic therapy
Hepatology/nephrology/haematology referralWhen cholestasis, CKD-related pruritus, polycythaemia, lymphoma, or other systemic disease is identified
Management Principles
MCC Pruritus objective + Canadian Dermatology Association resources1
General itch measures
- Use liberal fragrance-free emollients, short lukewarm showers, gentle cleansers, humidification, and avoidance of wool/fragrances/irritants
- Keep nails short, reduce scratching triggers, and manage sleep disruption
- Topical corticosteroids help inflammatory dermatoses but do not treat systemic itch without inflammation
2
Treat common dermatologic causes
- Xerosis/eczema: emollients plus topical corticosteroids matched to body site and severity
- Urticaria: second-generation non-sedating antihistamines; avoid routine extensive allergy testing unless history supports it
- Scabies: permethrin 5% cream to entire body as directed, repeat in 7 days; treat all close contacts and decontaminate bedding/clothing
3
Treat systemic causes
- Cholestasis: investigate and treat obstruction or liver disease; specialist-directed therapies may include bile-acid sequestrants or other agents
- CKD-related pruritus: optimize dialysis/CKD care, emollients, and nephrology-directed therapies
- Iron deficiency, thyroid disease, diabetes, polycythaemia vera, or malignancy: treat the underlying diagnosis
4
Escalate when red flags are present
- Urgent evaluation for jaundice, B symptoms, abnormal CBC, renal failure, pregnancy cholestasis symptoms, severe infestation in institutions, or immunocompromise
- Dermatology referral for refractory, unexplained, severe, or diagnostically uncertain pruritus
Complications & Pitfalls
- Confusing excoriations with primary rash: Scratch marks may hide systemic disease; look for true primary lesions.
- Missing scabies: Nocturnal itch and household spread are more important than seeing a burrow.
- Over-testing urticaria: Most acute urticaria does not need large allergy panels unless a specific trigger history exists.
- Ignoring cholestasis in pregnancy: Pruritus without rash in pregnancy, especially palms/soles, needs urgent obstetric assessment.
- Using topical steroids alone for generalized systemic itch: Treat the underlying renal, liver, haematologic, endocrine, or medication cause.
MCCQE1 Exam Tips
- 1The MCC pruritus objective explicitly emphasizes differentiating excoriations from primary skin lesions
- 2Itch with no rash is a systemic-workup question: CBC/ferritin, renal function, liver tests, and targeted thyroid/glucose testing
- 3Nocturnal itch in several household members = scabies; treat the patient and contacts at the same time
- 4Aquagenic pruritus is a classic clue for polycythaemia vera
- 5Jaundice or cholestatic labs change the problem from dermatology to hepatobiliary medicine
- 6Acute urticaria with no anaphylaxis is usually treated with non-sedating antihistamines, not broad allergy testing
- 7Pruritus in pregnancy without rash should raise intrahepatic cholestasis of pregnancy, requiring obstetric involvement
practicetest your knowledge on pruritusApply what you've learnt with MCCQE1-style questions from the iatroX Q-Bank — dermatologic and beyond.
open q-bank