CFB FM02 Introduction To Common Problems - Differentiating The Normal From The Abnormal
An introductory clinical framework for distinguishing physiological (normal) findings from pathological (abnormal) findings when evaluating common patient presentations through systematic comparison of expected versus deviant signs, symptoms, and laboratory values.
Introduction to Common Problems: Differentiating the Normal from the Abnormal
This lecture by Dr Julie Chen is a Clinical Foundation Block (CFB) Family Medicine session that sets the philosophical and practical framework for how doctors in primary care decide whether a patient's complaint represents disease or normality. It is the intellectual backbone of clinical reasoning in primary care and underpins every other topic you will encounter in General Clerkship.
The big idea: Most patients present with symptoms, not diagnoses. Your job is to figure out whether the symptom represents something normal (a physiological variant, a self-limiting process) or something abnormal (a disease requiring intervention). This lecture teaches you the thinking tools to do that safely and systematically.
Learning Objectives [1]
By the end of this lecture you will be able to:
- Recognize the factors that determine when a presenting problem is "abnormal."
- Describe common presenting problems in primary care and relate them to specific diagnoses.
Core Concept — High Yield
A disease is "a departure from normal," but defining "normal" depends on the lens you use. [1]
Three Lenses for Defining Abnormality [1]
| Lens | Definition of "Abnormal" | Example | Why It Matters |
|---|---|---|---|
| Statistical | > 2 standard deviations from the mean | BP > 140/90 mmHg | Provides objective, measurable thresholds. But a value can be statistically abnormal yet clinically irrelevant (e.g., someone 2 SD taller than mean is not "diseased"). |
| Statistical (risk-based) | "Increased risk of morbidity or mortality" | HbA1c ≥ 6.5% → increased risk of microvascular complications | This is how most clinical thresholds are set — the cutoff is chosen where risk materially increases. |
| Socio-cultural | "Not culturally desirable" | Obesity viewed differently across cultures; homosexuality was once classified as a psychiatric disease | Reminds us that medical definitions are not purely objective — context matters. This is directly relevant to psychiatry classifications [2]. |
| Individual perception | "I don't feel well" | A patient with fatigue but entirely normal investigations | The patient's subjective experience is valid and must be explored, even if no organic cause is found. Illness ≠ disease. |
First-principles explanation: Medicine tries to use objective criteria (statistics, risk thresholds) to define disease. But in primary care, the patient presents with illness (their subjective experience), and you must determine whether an underlying disease exists. These three lenses remind you that "abnormal" is not always black and white.
The factors that influence how normal is differentiated from the abnormal are: Evidence, Experience, and Context. [1]
High Yield — Exam Favourite
"Common things are COMMON." When hearing hoofbeats, think horses, not zebras. [1]
The Two Key Principles [1]
- Common diseases are common — URTI, DM, HT, gastroenteritis dominate primary care.
- It is far more likely to encounter UNCOMMON presentations of COMMON problems than COMMON presentations of UNCOMMON problems.
| Scenario | Example | Clinical Implication |
|---|---|---|
| Uncommon presentation of a COMMON disease | Itchy feet as the presenting symptom of DM (peripheral neuropathy → pruritus) | You must think broadly about common diagnoses. DM can present with anything from polyuria to a foot ulcer to blurred vision to pruritus. |
| Common presentation of an UNCOMMON disease | Kayser-Fleischer rings + fatigue + jaundice + coordination problems = Wilson's disease | Dramatic but rare — don't anchor on rare diagnoses when common ones haven't been excluded. |
Why this matters for exams: When given a clinical vignette, your first differential should always be the most common cause for that age/sex/context. Only after considering and excluding common diagnoses should you move to rarer ones.
High Yield — Framework for Every Clinical Encounter
This is THE systematic approach to problem-solving in primary care that the lecture explicitly teaches. Expect this to be tested. [1]
Be systematic in problem solving:
- What is the probability diagnosis? — The most likely diagnosis based on epidemiology.
- What serious disorders cannot be missed (red flags)? — Conditions where delayed diagnosis = disaster.
- What conditions are often missed (pitfalls)? — Diagnoses that clinicians commonly overlook.
- Could this patient have a 'masquerade'? — A medical condition mimicking a different problem (e.g., depression masquerading as fatigue; hypothyroidism masquerading as cognitive decline).
- Is this patient trying to tell me something else (hidden agenda)? — The real reason for the visit may not be the stated complaint. [1]
From Murtagh's General Practice, 2022 [1]
Explaining Each Step from First Principles
Probability diagnosis: Bayesian reasoning — your pre-test probability is set by the prevalence of diseases in your practice population. In HK primary care, URTI and hypertension are vastly more common than Addison's disease.
Red flags (can't miss): These are conditions where missing the diagnosis leads to irreversible harm or death. Even if the probability is low, the consequences are so severe that you must actively exclude them. Examples: cauda equina syndrome in back pain, subarachnoid haemorrhage in headache, ectopic pregnancy in abdominal pain.
Pitfalls (often missed): These are diagnoses that are common enough but get overlooked because clinicians don't think of them. Example: depression presenting as fatigue — only ~15% of fatigue has an organic cause, but clinicians may not screen for depression.
Masquerades: A small number of conditions can present as almost anything. Classic masquerades include: depression, DM, thyroid disease, anaemia, drugs/medications, UTI (in elderly). The concept: always consider whether one of these "great mimickers" could explain the presentation.
Hidden agenda: The patient presents with a headache but is actually worried about a brain tumour because a relative just died of one. Or the patient presents with insomnia but is actually experiencing domestic violence. If you don't explore the patient's concerns, expectations, and fears (ICE framework from FM01), you will miss the real problem.
4. Most Common Problems in HK Primary Care
The lecture presents data from two HKCFP Primary Care Morbidity Surveys — this is HK-specific epidemiology that is highly testable.
| Rank | 2007-08 Survey | 2021-22 Survey |
|---|---|---|
| 1 | URTI / Influenza | Hypertension |
| 2 | Hypertension | Lipid disorder |
| 3 | DM | DM |
| 4 | Gastroenteritis | URTI |
| 5 | Lipid disorder | Dermatitis |
| 6 | Dermatitis | Gastroenteritis |
| 7 | Acute bronchitis | Allergic rhinitis |
| 8 | Allergic rhinitis | Dyspepsia |
| 9 | Dyspepsia | Obesity |
| 10 | Abdominal pain | OA knee |
| 11 | Asthma | Gout |
| 12 | Anxiety | Depressive disorder |
Key observations:
- Chronic diseases (HT, DM, lipid disorder) have risen in ranking, reflecting the ageing population and metabolic epidemic.
- Obesity, OA knee, gout, and depressive disorder are new entries in the 2021-22 survey — reflecting changing disease patterns.
- COVID and abnormal results also appeared as new categories.
- Infection-related diagnoses (URTI, GE) dropped in relative ranking but remain extremely common.
This is a ranked list from the HKCFP 2021-22 survey — know at least the top 10.
| Rank | Symptom | Rank | Symptom |
|---|---|---|---|
| 1 | Cough | 18 | Fever/chills |
| 2 | Skin rash/itch | 19 | Feeling anxious |
| 3 | Nasal congestion, runny nose | 20 | Limb pain |
| 4 | Dyspepsia | 21 | Constipation |
| 5 | Back pain | 22 | Ear pain/hearing |
| 6 | Sore throat | 23 | Neck pain/discomfort |
| 7 | Diarrhoea | 24 | Sleep disturbance |
| 8 | Dysuria, urinary frequency | 25 | Shoulder pain |
| 9 | Eye complaints (red eye, visual disturbance) | 26 | Hand/wrist/elbow pain |
| 10 | Abdominal pain | 27 | Palpitations |
| 11 | Foot/toe pain | 28 | General malaise |
| 12 | Headache | 29 | Oral/dental pain/lesions |
| 13 | Chest pain | 30 | Localized lump |
| 14 | Dizziness | 31 | Nausea, vomiting |
| 15 | Knee pain | 32 | Shortness of breath |
| 16 | Menstrual/vaginal complaints | 33 | Numbness, tingling |
| 17 | Skin lesions/injury | 34 | Rectal bleeding |
5. Symptom-by-Symptom Clinical Approach
The lecture walks through 8 key presenting symptoms using Murtagh's safe diagnostic model. Each is covered below in detail.
5.1 Fatigue
Key Principle
Chronic fatigue is not normal. But the vast majority of cases (~85%) do NOT have an organic cause. [1]
Differentiate between fatigue from organic disease and fatigue from anxiety/depression. Only about 15% have an organic cause. [1]
Why only 15% organic? Because fatigue is an extremely non-specific symptom. It is the final common pathway of almost every disease AND of psychological distress. In primary care populations (where serious disease prevalence is low), the pre-test probability of organic disease is inherently low.
"Consider infectious, anaemia, endocrine, sleep disturbances, medications, and malignancy."
| Category | Examples | Why to Consider |
|---|---|---|
| Infection | Viral illness (EBV, CMV, hepatitis), HIV, TB | Acute fatigue post-viral is extremely common; chronic infections are rarer but important |
| Anaemia | Iron deficiency, B12/folate deficiency, thalassaemia trait | Reduced oxygen-carrying capacity → tissue hypoxia → fatigue |
| Endocrine | Hypothyroidism, DM, Addison's disease, hypercalcaemia | Metabolic derangement → cellular energy deficiency |
| Sleep disturbances | Obstructive sleep apnoea, insomnia | Poor sleep quality → daytime fatigue; OSA is under-diagnosed |
| Medications | Beta-blockers, antihistamines, antidepressants, statins | Always ask about drug history — iatrogenic fatigue is a pitfall |
| Malignancy | Any cancer (lung, GI, haematological) | Weight loss + fatigue = red flag |
| Age < 45 | Age > 45 | |
|---|---|---|
| Most common | Fatigue NYD (45.8%) | Fatigue NYD (36.6%) |
| 2nd | Viral illness (11.8%) | Viral illness (8%) |
| 3rd | Depression / Anxiety / Stress (6.6%) | Depression / Anxiety / Stress (7.5%) |
| Others | Anaemia, sinusitis, mono | Anaemia, CHF, medication, DM, COPD, IHD |
"NYD" = Not Yet Diagnosed — this means that even after workup, nearly half of patients under 45 with fatigue will have no identifiable cause. This is normal in primary care — the diagnosis is often "idiopathic fatigue" or a subclinical psychological issue.
The lecture presents the full Murtagh table (Table 63.2) for tiredness/chronic fatigue:
| Category | Diagnoses |
|---|---|
| Probability diagnosis | Stress and anxiety; depression; inappropriate lifestyle and psychosocial factors; viral/postviral infection; sleep-related disorders (e.g. sleep apnoea) |
| Serious disorders not to be missed | Vascular: cardiac arrhythmias, cardiomyopathy, incipient CCF · Infection: hidden abscess, HIV/AIDS, hepatitis B and C · Cancer: any malignancy · Other: anaemia, haemochromatosis |
| Pitfalls (often missed) | 'Masked' depression; coeliac disease; chronic infection (e.g. Lyme disease); incipient CCF; fibromyalgia; lack of fitness; drugs (alcohol, prescribed, withdrawal); menopause syndrome; pregnancy · Neurological: post head injury, CVA, Parkinson disease · Other: kidney failure, metabolic (e.g. hypokalaemia, hypomagnesaemia), chemical exposure (e.g. occupational) |
| Rarities | Hyperparathyroidism, Addison disease, Cushing syndrome, narcolepsy, multiple sclerosis, autoimmune disorders |
| Seven masquerades checklist | Depression, Diabetes, Drugs, Anaemia, Thyroid disease (other endocrine), Spinal dysfunction, UTI |
| Is the patient trying to tell me something? | Highly likely. |
Key difference by age: In patients > 45, you see more serious organic causes (CHF, DM, COPD, IHD) — this is why age matters in your differential.
Chronic fatigue syndrome is a specific clinical diagnosis.
CFS (also called Myalgic Encephalomyelitis, ME/CFS) is diagnosed when:
- Fatigue lasting ≥ 6 months
- Substantially reduces activity level
- Not explained by another medical condition
- Post-exertional malaise is a hallmark
- Unrefreshing sleep
- Cognitive impairment ("brain fog")
Why is it important to distinguish CFS from general fatigue? Because CFS requires specific management (pacing, graded exercise therapy is controversial, CBT), and mislabelling can lead to inappropriate investigations or dismissal of the patient's experience.
5.2 Low Back Pain
High Yield
Mechanical back pain is by far the most common cause. But you must actively exclude serious causes. [1]
- Serious causes: neoplasm, infections, cauda equina syndrome — these are the "can't miss" diagnoses.
- Visceral causes — referred pain from kidney stones, aortic aneurysm, pancreatitis, pelvic pathology.
- Inflammatory causes — ankylosing spondylitis (young male, morning stiffness > 30 min, improves with exercise).
- Role of X-ray — generally NOT useful for acute mechanical LBP. Imaging is reserved for red flags.
Why is imaging not useful? Because degenerative changes on X-ray are ubiquitous in adults and do not correlate with symptoms. You might find disc degeneration in an asymptomatic 50-year-old and normal imaging in someone with severe sciatica. Imaging can lead to over-diagnosis and unnecessary interventions.
| Red Flag | Suggests |
|---|---|
| Age > 50 with new onset | Malignancy, vertebral fracture |
| History of cancer | Metastatic disease |
| Unexplained weight loss | Malignancy |
| Fever | Spinal infection (discitis, epidural abscess) |
| IV drug use | Spinal infection |
| Immunosuppression | Infection |
| Progressive neurological deficit | Cauda equina syndrome |
| Saddle anaesthesia, urinary retention, bowel incontinence | Cauda equina syndrome — surgical emergency |
| Night pain not relieved by rest | Malignancy, infection |
| Significant trauma | Fracture |
| Age < 45 | Age > 45 | |
|---|---|---|
| Most common | Mechanical LBP (67%) | Mechanical LBP (59%) |
| 2nd | Sciatica (8%) | DDD (9.6%) |
| 3rd | Muscle strain (6.3%) | Sciatica (8.5%) |
| 4th | DDD (4.8%) | Muscle strain (3.8%) |
DDD = Degenerative Disc Disease — becomes more prominent with age, as expected.
The lecture presents the full Murtagh table (Table 28.1) for low back pain:
| Category | Diagnoses |
|---|---|
| Probability diagnosis | Vertebral dysfunction (non-specific LBP); musculoligamentous strain/sprain; spondylosis (degenerative OA) |
| Serious disorders not to be missed | Cardiovascular: ruptured aortic aneurysm, retroperitoneal haemorrhage (anticoagulants) · Neoplasia: myeloma, carcinoma of pancreas, metastases · Severe infections: vertebral osteomyelitis, epidural abscess, septic discitis, tuberculosis, pelvic abscess/PID · Other: osteoporotic compression fracture/other fracture, cauda equina compression |
| Pitfalls (often missed) | Spondyloarthropathies: ankylosing spondylitis, reactive arthritis, psoriasis, bowel inflammation · Claudication: vascular, neurogenic/spinal canal stenosis · Other: sacroiliac dysfunction, spondylolisthesis, Paget disease, prostatitis, endometriosis |
| Seven masquerades checklist | Depression, spinal dysfunction, UTI |
| Is the patient trying to tell me something? | Quite likely. Consider lifestyle, stress, work problems, malingering, conversion reaction. |
5.3 Skin Complaints
High Yield
The lecture covers three main skin presentations: itchy rash, growth on skin, and moles. Know the top 5 skin diagnoses in HK. [1]
| Rank | Diagnosis | Incidence (% of 9301 new cases) |
|---|---|---|
| 1 | Eczema (all types) | 1193 (13%) |
| 2 | Seborrhoeic keratosis | 586 (6%) |
| 3 | Warts (excl. genital) | 481 (5%) |
| 4 | Tinea | 375 (4%) |
| 5 | Psoriasis | 196 (2%) |
| Type | Key Features | Distribution | Why It Matters |
|---|---|---|---|
| Atopic eczema | Prominent pruritus; chronic/relapsing; personal/family hx of atopy; dry skin, hyperlinearity of palms, keratosis pilaris, raised IgE, early onset, tendency to cutaneous infection, cheilitis, pityriasis alba | Flexural areas (antecubital, popliteal fossae) in older children/adults; face/extensors in infants | Most common type; the "classic" eczema |
| Asteatotic eczema | Commonly in elderly; dry season or central heating; dry, slightly scaly, criss-crossed ("crazy paving" pattern) | Limbs, especially legs | Often missed in elderly — looks like dry skin but is eczema |
| Stasis eczema | Over ankles; associated with varicose veins; aetiology: venous insufficiency, minor trauma/scratching, allergy to topical medications | Medial ankle/lower leg | Key association with chronic venous insufficiency |
| Discoid (nummular) eczema | Circumscribed or oval plaques of eczema; once established, lesions remain in same area | Extremities, can be generalized | Can be confused with tinea corporis — but nummular eczema lacks the central clearing of tinea |
| Lichen simplex chronicus | Thickened skin with accentuation of surface markings; circumscribed; resulted from repeated scratching/rubbing | Nape of neck, ankles, wrists | The itch-scratch cycle — secondary to chronic rubbing |
| Contact dermatitis | Irritant or allergic; distribution matches the contactant | Varies (hands for occupational, face for cosmetics, etc.) | History of exposure is the key diagnostic clue |
Dermatophytes (tinea) and yeasts (candida). Commensal organisms that thrive in warm, moist environments. Contagious; secondary bacterial infection can occur.
Why this matters: Tinea can mimic eczema (especially nummular eczema). The key differentiator is KOH preparation showing hyphae, and the characteristic annular, advancing border with central clearing in tinea corporis.
Benign skin growths include warts, moles, or corns — rarely serious. Main types of malignant skin cancer: malignant melanoma, BCC, SCC. [1]
Must Know — ABCDE Criteria
A = Asymmetry: irregular shape B = Border: ragged outline C = Colour: variation of colour D = Diameter: bigger than 6mm across and/or recent increase in size E = Elevation: raised above surface of skin [1]
Why each criterion matters:
- Asymmetry: Normal moles are round/oval. Asymmetry suggests disordered growth.
- Border irregularity: Normal moles have smooth edges. Irregular borders suggest invasion.
- Colour variation: Multiple colours (brown, black, red, white, blue) suggest different clones of melanocytes at varying depths.
- Diameter > 6mm: Larger lesions have had more time to grow and are more likely to be malignant.
- Elevation: Raised areas suggest vertical growth phase (deeper invasion = worse prognosis).
Connection to GC 201 (Skin ulcers, skin lesions, skin cancer): The GC lecture on skin cancer goes into more detail on BCC (pearly, rolled border, telangiectasia), SCC (keratinized, crusted), and melanoma subtypes. This CFB lecture provides the primary care approach to the same topic.
High Yield
Most likely diagnosis: viral gastroenteritis. But you MUST NOT miss an acute abdomen. [1]
Key Points [1]
- "Does the patient look toxic?" — This is the single most important clinical question. A toxic-looking patient needs urgent investigation/referral.
- Must not miss acute abdomen — appendicitis, perforated viscus, bowel obstruction, ectopic pregnancy, ruptured AAA.
- Examine abdomen including muscle — look for guarding (involuntary muscle contraction = peritoneal irritation).
- Do rectal exam if unsure — can reveal melaena, masses, or tenderness in the pouch of Douglas.
- Testes (male), pregnancy test (female) — testicular torsion is a surgical emergency; ectopic pregnancy is a life-threatening cause of abdominal pain in women of reproductive age.
- Follow up next day if in doubt — safety-netting is a core primary care skill. If you're uncertain, bring the patient back.
From first principles: The danger in abdominal pain is missing a surgical emergency. The primary care clinician's job is not necessarily to make the exact diagnosis, but to triage: is this patient safe to go home, or do they need hospital assessment?
5.5 Headache
High Yield — Red Flags for Headache
Learn these red flags — they are the "can't miss" list for headache. [1]
| Red Flag | Why | Suggests |
|---|---|---|
| Worst headache of life | Sudden onset, maximal intensity | Subarachnoid haemorrhage |
| Visual loss or other neurological deficits | Focal signs suggest structural lesion | Space-occupying lesion, stroke |
| New onset in elderly | New headache in > 50 y/o | Temporal arteritis (GCA), malignancy |
| Positional or worsening with Valsalva | Raised intracranial pressure | Space-occupying lesion, Chiari malformation |
| Morning headache | ICP highest when lying flat overnight | Raised ICP (tumour) |
| Headache in pregnancy | Pre-eclampsia, cerebral venous thrombosis | Eclampsia, CVT |
| Trauma or anticoagulation | Risk of intracranial bleed | Subdural/extradural haematoma |
| History of carcinoma | Risk of brain metastases | Cerebral metastases |
- "Ask about drugs" — medication overuse headache is extremely common and often missed (analgesic rebound headache from using painkillers > 15 days/month).
- "Explore patient's fears" — many patients with headache are worried about a brain tumour. Addressing this fear is therapeutic.
- "Don't forget functional/psychiatric causes" — tension headache is often associated with stress, anxiety, depression.
| Age < 45 | Age > 45 | |
|---|---|---|
| Most common | Headache NYD (26%) | Headache NYD (28%) |
| 2nd | Sinusitis (13%) | Cervical disease (11%) |
| 3rd | Tension (10%) | Tension (8.6%) |
| 4th | Migraine (6.7%) | Sinusitis (8.4%) |
| 5th | Cervical disease (5.4%) | — |
Key shift: Cervical disease (cervicogenic headache) becomes the 2nd most common cause in patients > 45.
Core Approach
The first step is to CLARIFY what the patient means by "dizziness." [1]
Why? Patients use "dizziness" to describe at least four different sensations:
- Vertigo — a spinning sensation (room spinning or patient spinning) → vestibular origin
- Pre-syncope / light-headedness — feeling about to faint → cardiovascular origin (orthostatic hypotension, arrhythmia)
- Disequilibrium — unsteadiness/imbalance → neurological/musculoskeletal origin
- Non-specific dizziness — vague, hard to describe → often anxiety, hyperventilation, medication side effects
Key Points [1]
- Central vs peripheral — distinguish central vertigo (brainstem/cerebellar, e.g., stroke, MS) from peripheral vertigo (inner ear, e.g., BPPV, vestibular neuritis). Central causes have associated neurological signs (diplopia, dysarthria, ataxia, cranial nerve palsies).
- Red flags — sudden onset with neurological deficits (posterior circulation stroke), hearing loss with vertigo (Ménière's disease), acute onset in elderly with vascular risk factors.
- Most common diagnosis of true vertigo is "vertigo NYD."
- Acute vertigo common causes:
- Viral labyrinthitis
- BPV (Benign Paroxysmal Vertigo / BPPV)
- Eustachian tube dysfunction
- Ménière's disease
5.7 Chest Pain
High Yield
A good history is key. The strongest predictors of ACS are age, sex, and type of chest pain. [1]
Typical angina: deep, poorly localized chest or arm discomfort (pain or pressure) associated with physical exertion or emotional stress and relieved with rest or sublingual NTG.
To classify chest pain as typical angina, it must have all three features:
- Substernal chest discomfort of characteristic quality and duration
- Provoked by exertion or emotional stress
- Relieved by rest or NTG
Atypical angina = 2 of 3 features. Non-cardiac chest pain = 0-1 features.
| Age (years) | Men: Typical | Men: Atypical | Men: Non-anginal | Women: Typical | Women: Atypical | Women: Non-anginal |
|---|---|---|---|---|---|---|
| 40–49 | 69% | 38% | 25% | 37% | 14% | 8% |
| 50–59 | 77% | 49% | 34% | 47% | 20% | 12% |
| 60–69 | 84% | 59% | 44% | 58% | 28% | 17% |
| 70–79 | 89% | 69% | 54% | 68% | 37% | 24% |
| ≥ 80 | 93% | 77% | 65% | 76% | 47% | 32% |
Key points: Pretest probability rises steeply with age and is consistently higher in men than women for every chest pain category. Even non-anginal chest pain in a man ≥ 80 carries a 65% pretest probability of CAD. This table operationalises why age, sex, and type of chest pain are the strongest predictors of ACS.
- Also consider risk factors and precipitating factors — hypertension, DM, smoking, family history, hyperlipidaemia.
- Normal resting ECG does not rule out ischaemia — a resting ECG may be completely normal between episodes of angina. Exercise stress testing or CT coronary angiography may be needed.
| Common | Can't Miss |
|---|---|
| Chest wall pain | IHD |
| GERD | Pulmonary embolus |
| Costochondritis | Aortic dissection |
| Anxiety | Tension pneumothorax |
| Pneumonia |
Exam Trap
Don't assume chest pain = cardiac. In primary care, chest wall pain, GERD, costochondritis, and anxiety are far more common than IHD. But you MUST actively exclude the "can't miss" diagnoses before concluding benign cause.
5.8 Vaginal Complaints
High Yield
Know how to differentiate normal from abnormal vaginal discharge. [1]
| Symptom | Common Diagnoses |
|---|---|
| Itching | Candidiasis, contact dermatitis, atrophic vulvitis |
| Odour | Bacterial vaginosis, trichomoniasis |
| Pain | Infection, vulvodynia |
| Discharge | Physiological, infective (candida, BV, STIs), cervical ectropion |
| Bleeding | Cervical polyp, cervical ectropion, neoplasm, retained products, menstrual irregularities |
The lecture shows cervix photographs at different days of the menstrual cycle (Days 14, 17, 27), demonstrating that:
- Normal discharge varies throughout the cycle: clear and stretchy (like egg white) around ovulation (day 14), becoming thicker and whiter in the luteal phase (day 27).
- Cervical ectropion (previously called "cervical erosion") is a normal finding — columnar epithelium extends onto the ectocervix, appearing red. It is NOT a pathological condition and does NOT require treatment unless symptomatic.
Normal cervix images are shown — learn to recognize normal so you can identify abnormal. [1]
- Post-coital spotting → must exclude cervical pathology (cervical ectropion is common and benign, but cervical carcinoma must be ruled out with a smear/colposcopy if warranted).
- Vaginal itching → most commonly candidiasis (thick white "cottage cheese" discharge, vulval erythema), but consider contact dermatitis and atrophic vulvitis in postmenopausal women.
Factors that influence how normal is differentiated from the abnormal:
- Evidence
- Experience
- Context
Recognizing common problems:
- Epidemiology
Approach to diagnosing them:
- Can't miss (red flags)
- Often missed (pitfalls)
- Masquerades
- Hidden agenda
8. Integration with Related Material
FM01 teaches the biopsychosocial model, continuity of care, and the ICE framework (Ideas, Concerns, Expectations). This lecture builds directly on FM01 by applying those concepts to symptom interpretation. The "hidden agenda" step in Murtagh's model is essentially the ICE framework in action.
The socio-cultural definition of abnormality directly parallels the challenges of psychiatric classification. As Ryan Ho's Psychiatry notes state: "Non justifiable to make arbitrary cut-off point between normal and abnormal" — the same principle applies in somatic medicine [2].
GC 022 directly states: "Distinguish the abnormal from the normal; describe the abnormality." This is the same competency tested in a visual format — recognizing normal cervix, normal skin variants, etc.
Past Fourth Summative papers frequently test:
- "What is the most likely diagnosis?" → tests probability diagnosis
- "What red flag features would you look for?" → tests can't-miss diagnoses
- "Name 3 differential diagnoses for..." → tests systematic approach
- Dermatology spot diagnosis → tests ABCDE, eczema types, skin cancer recognition
9. Exam Intelligence
| Format | Example Stem | What They're Testing |
|---|---|---|
| MCQ | "A 35-year-old woman presents with fatigue for 3 months. Normal CBP, TFT, glucose. What is the most likely diagnosis?" | Fatigue NYD is the most common diagnosis — don't over-investigate |
| MCQ | "Which of the following is NOT a red flag for headache?" | Knowledge of red flag list |
| SAQ | "Describe Murtagh's safe diagnostic model and give an example for each step using back pain." | Framework recall + application |
| SAQ | "A 65-year-old presents with a skin lesion. What features would make you suspect melanoma?" | ABCDE criteria |
| Minicase | Patient with chest pain — differentiate cardiac from non-cardiac | History features of typical angina; can't-miss diagnoses |
| OSCE | Patient with "dizziness" — clarify the symptom | Four types of dizziness; central vs peripheral vertigo |
Common Exam Traps
- Assuming organic cause for fatigue: ~85% are non-organic. The probability diagnosis is fatigue NYD or depression/anxiety.
- Ordering X-ray for acute mechanical LBP: Not indicated without red flags. Degenerative changes are ubiquitous and don't correlate with symptoms.
- Confusing "cervical ectropion" with pathology: It is NORMAL, not "cervical erosion."
- Dismissing normal resting ECG: A normal resting ECG does NOT rule out ischaemic heart disease.
- Forgetting masquerades: Depression, DM, thyroid disease, anaemia, and drugs can present as almost any symptom.
- Not exploring hidden agenda: Marks are given in OSCE for exploring patient concerns/fears.
For Murtagh's model questions:
- "The probability diagnosis for [symptom] in a [age/sex] patient is [diagnosis] because it is the most common cause in this demographic."
- "Red flags that cannot be missed include [list], because delayed diagnosis of [condition] leads to [irreversible consequence]."
- "Masquerades to consider include depression, DM, thyroid disease, anaemia, and medications."
High Yield Summary
-
Core Framework
- Use Murtagh's Safe Diagnostic Model for every undifferentiated symptom — (1) Probability diagnosis, (2) Red flags (can't miss), (3) Pitfalls (often missed), (4) Masquerades, (5) Hidden agenda.
-
Defining abnormality
- Statistical ( > 2 SD, increased risk), socio-cultural ("not desirable"), individual perception ("I don't feel well"). The answer depends on evidence, experience, and context.
-
Epidemiology drives your differential
- Common things are common. In HK primary care, the top diagnoses are HT, lipid disorder, DM, URTI, dermatitis. Top symptoms are cough, skin rash, nasal congestion, dyspepsia, back pain.
-
Key clinical pearls
- (1) 85% of fatigue is non-organic. (2) Mechanical LBP accounts for 60-67% of back pain. (3) Eczema is the #1 skin diagnosis. (4) ABCDE for melanoma. (5) In chest pain, chest wall/GERD/costochondritis/anxiety are common; IHD/PE/dissection/tension pneumothorax/pneumonia are can't-miss. (6) Normal resting ECG does NOT exclude IHD. (7) Cervical ectropion is NORMAL. (8) Always explore the hidden agenda.
Active Recall - Lecture Notes
[1] Lecture slides: CFB (FM02) Introduction to common problems - Differentiating the normal from the abnormal.pdf (all pages) [2] Senior notes: Ryan Ho Psychiatry.pdf (p4 — Classification in Psychiatry, normal vs abnormal cut-off) [3] Lecture slides: CFB (FM01) Principles and concepts of Family Medicine.pdf [4] Lecture slides: GC 022. Visual Spot Diagnoses - Survival Guide for Primary Care.pdf (p2)
CFB PAE03 Immunization
Immunization is the process of inducing protective immunity against infectious diseases through the administration of vaccines (active immunization) or preformed antibodies (passive immunization).
CFB MED12 Introduction To Geriatric Medicine
Geriatric medicine is the branch of medicine focused on the diagnosis, treatment, and prevention of disease and disability in older adults, emphasizing functional status, multimorbidity, and comprehensive assessment.