Look first. Think clinically. The diagnosis is deliberately hidden. Use the visual pattern and short clue, commit to an answer, then tap Diagnosis to reveal the explanation.
A 28-year-old has sharply demarcated erythematous plaques with silvery scale over extensor surfaces.
Key identifying features: Well-defined plaques, extensor distribution and silvery scale are classic clues.
An itchy annular lesion has an active scaly edge with relative central clearing.
Key identifying features: An enlarging annular plaque with peripheral scale and central clearing suggests dermatophyte infection.
Pain and burning were followed by grouped vesicles confined to one side of the chest.
Key identifying features: Grouped vesicles in a unilateral dermatomal distribution are highly characteristic.
There are sharply marginated depigmented macules without surface scale.
Key identifying features: Complete depigmentation with a smooth surface and clear border is typical.
A child develops superficial erosions around the nose with golden-yellow crusting.
Key identifying features: Honey-coloured crust over superficial erosions is a classic appearance.
Symmetric round lesions have three concentric zones with a dusky centre.
Key identifying features: Classic target lesions have concentric colour zones and often involve acral surfaces.
There is intense nocturnal itching with papules and fine burrows in the finger webs.
Key identifying features: Nocturnal pruritus, household spread and burrows in finger webs are strong clues.
Transient raised itchy lesions appear and fade within hours without leaving scale.
Key identifying features: Evanescent pruritic wheals that migrate and resolve within 24 hours are typical.
A young woman has erythema over both cheeks and nasal bridge, relatively sparing the nasolabial folds.
Key identifying features: A photosensitive malar distribution that spares the nasolabial folds is a classic lupus clue.
There is violaceous eyelid discoloration with papules over the knuckles and proximal muscle weakness.
Key identifying features: Heliotrope rash and Gottron papules with proximal weakness strongly suggest dermatomyositis.
Tender red nodules are present over both shins in a patient with fever and joint pain.
Key identifying features: Painful subcutaneous nodules on the anterior shins are characteristic.
One lower leg is acutely red, warm, swollen and tender with an ill-defined advancing margin.
Key identifying features: Unilateral warmth, tenderness, erythema and swelling with poorly demarcated borders fit cellulitis.
Recurrent grouped painful vesicles occur at the lip border after fever or sun exposure.
Key identifying features: Grouped vesicles on an erythematous base at the vermilion border are typical.
Creamy white plaques cover the tongue and buccal mucosa and can be scraped away leaving erythema.
Key identifying features: Removable white plaques with an erythematous base suggest oral thrush.
Painful fissuring and erythema are present at both angles of the mouth.
Key identifying features: Inflamed fissures at the oral commissures are typical.
The sclera and skin have a yellow discoloration in a patient with dark urine.
Key identifying features: Scleral icterus is often an early visible clue to elevated bilirubin.
The tongue and oral mucosa have a bluish colour in a breathless patient.
Key identifying features: Bluish discoloration of the tongue and mucous membranes suggests central cyanosis.
The terminal phalanges are bulbous and the nail-fold angle is increased.
Key identifying features: Loss of the normal nail-fold angle and increased nail-bed sponginess are classic.
The nails are thin and concave with raised edges.
Key identifying features: Spoon-shaped nails are called koilonychia and classically suggest iron deficiency, although other causes exist.
Multiple painless erythematous macules are seen on the palms in a febrile patient with a murmur.
Key identifying features: Painless palm/sole lesions are a classic peripheral stigma of infective endocarditis.
A brown-golden ring is visible at the peripheral cornea in a young patient with liver and neurological features.
Key identifying features: Copper deposition in Descemet membrane produces a peripheral corneal ring.
Soft yellow plaques are present near the medial upper eyelids.
Key identifying features: Yellow cholesterol-rich eyelid plaques have a characteristic appearance.
Both eyes appear prominent with upper-lid retraction in a patient with tremor and weight loss.
Key identifying features: Proptosis and lid retraction in a hyperthyroid context strongly suggest thyroid eye disease.
One pupil is smaller and there is mild ipsilateral ptosis without major extraocular movement weakness.
Key identifying features: The combination of miosis and mild ptosis suggests interruption of the sympathetic pathway.
A patient cannot wrinkle the forehead, close one eye tightly or lift the corner of the mouth on one side.
Key identifying features: Weakness of the entire ipsilateral face including the forehead suggests a peripheral facial palsy.
Bilateral ptosis becomes more marked after sustained upward gaze and improves with rest.
Key identifying features: Fatigable ocular weakness, especially variable ptosis or diplopia, is characteristic.
Both hands show ulnar deviation at the MCP joints with chronic symmetrical swelling.
Key identifying features: Symmetrical MCP involvement with ulnar deviation is a classic late rheumatoid pattern.
A firm chalky nodule is present near the great toe with a history of recurrent acute monoarthritis.
Key identifying features: Tophi represent monosodium urate deposition in chronic gout.
Hard bony enlargements affect several distal interphalangeal joints.
Key identifying features: DIP bony enlargement is characteristic of hand osteoarthritis.
One ring finger is flexed by a firm palmar cord and cannot fully extend.
Key identifying features: Palmar fascial thickening forms cords that progressively flex the fingers.
A chest radiograph shows a visible pleural line with absent peripheral lung markings on one side.
Key identifying features: A visceral pleural line with no lung markings beyond it is the key radiographic clue.
There is homogeneous lower-zone opacity with a curved meniscus and blunting of the costophrenic angle.
Key identifying features: A meniscus with costophrenic-angle blunting is a typical radiographic pattern of pleural fluid.
A focal dense air-space opacity contains air bronchograms in one lower lobe.
Key identifying features: Air-space opacity with air bronchograms in a lobar distribution suggests consolidation.
Bilateral central fluffy opacities form a perihilar ‘bat-wing’ pattern with cardiomegaly.
Key identifying features: Perihilar air-space shadowing with cardiac enlargement and vascular congestion is a classic pattern.
The cardiac silhouette occupies more than half the internal thoracic width on an erect PA film.
Key identifying features: A cardiothoracic ratio greater than about 0.5 on a properly acquired PA film suggests cardiac enlargement.
Multiple centrally placed dilated bowel loops show several step-ladder air-fluid levels.
Key identifying features: Dilated central small-bowel loops and multiple air-fluid levels suggest mechanical obstruction.
An erect film shows a crescent of free gas beneath the right hemidiaphragm.
Key identifying features: Subdiaphragmatic free air on an erect radiograph strongly suggests perforation of a hollow viscus.
A knee radiograph shows asymmetric joint-space narrowing, marginal osteophytes and subchondral sclerosis.
Key identifying features: Joint-space loss with osteophytes and subchondral sclerosis is a classic degenerative pattern.
The rhythm strip is irregularly irregular with no consistent P waves.
Key identifying features: An irregularly irregular ventricular rhythm without discrete P waves is characteristic.
The ECG shows tall narrow tented T waves with progressive QRS widening.
Key identifying features: Peaked T waves and QRS widening are classic severe hyperkalaemic changes.
There is marked ST elevation across contiguous anterior precordial leads with reciprocal change.
Key identifying features: ST elevation in anatomically contiguous leads with a compatible presentation suggests acute coronary occlusion.
P waves march through independently of a slow regular QRS rhythm.
Key identifying features: Atrial and ventricular activity are dissociated, demonstrating third-degree AV block.
The PR interval is short and the initial QRS upstroke is slurred.
Key identifying features: Short PR interval and a delta wave indicate ventricular pre-excitation through an accessory pathway.
The blood film shows many small pale red cells with increased central pallor.
Key identifying features: Microcytosis and hypochromia suggest impaired haemoglobin synthesis, commonly iron deficiency or thalassaemia.
The smear shows macro-ovalocytes and a neutrophil with more than five nuclear lobes.
Key identifying features: Macro-ovalocytes and hypersegmented neutrophils strongly suggest megaloblastic change.
Several erythrocytes contain delicate ring-shaped intracellular parasites.
Key identifying features: Intraerythrocytic ring forms are a classic microscopic clue to malaria.
The blood film contains elongated crescent-shaped erythrocytes with target cells.
Key identifying features: Sickled erythrocytes are highly suggestive in the appropriate clinical context.
The film contains marked leukocytosis with granulocytes at multiple stages of maturation and basophils.
Key identifying features: A broad myeloid maturation spectrum with basophilia is characteristic of CML.
The face is coarse with frontal bossing and a broad jaw; the hands appear enlarged.
Key identifying features: Progressive acral enlargement and coarse facial features are classic manifestations of growth-hormone excess.
There is a rounded plethoric face, central adiposity and broad violaceous abdominal striae.
Key identifying features: Moon facies, central adiposity and wide purple striae are classic signs of glucocorticoid excess.