MTD 🩺

Medicine explained through cases & visuals.
Posts ≠ medical advice.

[MTD 🩺 @MTDMED]

Which antibiotics should be avoided with cheese?

[MTD 🩺 @MTDMED]

Why is pyridoxine given with isoniazid? ⚠️

[MTD 🩺 @MTDMED]

Which blood disorder presents with chipmunk facies?

[MTD 🩺 @MTDMED]

Can you identify this structure?

[MTD 🩺 @MTDMED]

🩺 Answer: Ethambutol

Ethambutol is classically associated with optic neuritis.

Key features

Decreased visual acuity
Central scotoma
Loss of red-green color discrimination (red-green color blindness)
Usually dose-related and often reversible if detected early

Monitoring

Baseline and periodic visual acuity and color vision testing are recommended during treatment.

High-yield anti-TB drug toxicities

Ethambutol → Optic neuritis
Isoniazid → Peripheral neuropathy (prevent with pyridoxine/Vitamin B6)
Rifampin → Orange-red body fluids
Pyrazinamide → Hyperuricemia, hepatotoxicity
Streptomycin → Ototoxicity, nephrotoxicity

Pearl
"E for Eye" → Ethambutol causes optic neuritis. 👁️

[MTD 🩺 @MTDMED]

⚠️ Which anti-tuberculosis drug is associated with optic neuritis?

[MTD 🩺 @MTDMED]

🩺 Think: Testicular cancer (especially a germ cell tumor).

A pregnancy test detects human chorionic gonadotropin (hCG). Some testicular germ cell tumors produce hCG, causing a urine pregnancy test to become positive in a male.

Most commonly associated tumors

Choriocarcinoma (markedly elevated hCG)
Some seminomas may also contain syncytiotrophoblastic giant cells that produce hCG

Clinical clues

Painless testicular mass
Testicular enlargement or heaviness
Gynecomastia (due to hCG-mediated hormonal effects)

Next step

Testicular examination and ultrasound
Serum tumor markers: β-hCG, AFP, and LDH

Pearl
A positive pregnancy test in a man is a classic exam clue for hCG-secreting testicular germ cell tumor until proven otherwise.

[MTD 🩺 @MTDMED]

🚨 A male patient took a pregnancy text as a joke and it came back positive!

What comes to your mind?

[MTD 🩺 @MTDMED]

🩺 Answer: C) ALT (Alanine aminotransferase)

ALT is the most specific enzyme for hepatocellular (liver cell) injury because it is found predominantly in hepatocytes.

Why not the others?

ALP → Marker of cholestasis and biliary obstruction; also found in bone and placenta.
AST → Present in liver, cardiac muscle, skeletal muscle, kidney, and brain, making it less liver-specific.
LDH → Found in many tissues throughout the body; very nonspecific.

High-yield pearl

ALT = most liver-specific
AST:ALT > 2 suggests alcoholic liver disease
Very high ALT/AST levels (>1000 U/L) are often seen in acute viral hepatitis, ischemic hepatitis, or toxin-induced liver injury.

[MTD 🩺 @MTDMED]

Which enzyme is most specific for liver cell injury?

[MTD 🩺 @MTDMED]

🩺 Diagnosis: Cerebrospinal fluid (CSF) otorrhea due to a basilar skull fracture

A patient with clear ear discharge after a road traffic accident should be presumed to have a basilar skull fracture involving the temporal bone causing leakage of CSF through the ear.

Supporting features

Clear, watery otorrhea
History of significant head trauma
May be associated with:Hemotympanum
Battle sign (mastoid ecchymosis)
Hearing loss
Facial nerve palsy
CSF rhinorrhea

How to confirm
Test the fluid for β2-transferrin (highly specific for CSF)
CT scan of the skull base/temporal bone
Pearl
In trauma questions, clear fluid draining from the ear = CSF otorrhea from a basilar skull fracture until proven otherwise.

[MTD 🩺 @MTDMED]

🚨 Patient presents with clear ear discharge following a road trafic accident.

What's the diagnosis?

[MTD 🩺 @MTDMED]

🩺 Coffee Bean Sign

The coffee bean sign on abdominal X-ray is classically associated with sigmoid volvulus.

Why it occurs

Twisting of the sigmoid colon around its mesenteric axis causes a massively dilated loop of colon.
The opposed medial walls of the dilated sigmoid loop create the appearance of a coffee bean.

Clinical features

Abdominal distension
Constipation/obstipation
Abdominal pain
Vomiting

Risk factors

Elderly patients
Chronic constipation
Neuropsychiatric disorders
Institutionalized or bedridden patients

Management

Stable patient: endoscopic detorsion and decompression
Peritonitis, ischemia, or perforation: urgent surgery

Other classic radiologic signs

Bird's beak sign (contrast enema or CT) → tapering at the site of torsion
Whirl sign (CT) → twisted mesentery and vessels

Pearl
☕ Coffee bean sign = Sigmoid volvulus until proven otherwise.

[MTD 🩺 @MTDMED]

Spot diagnosis? 🚨

[MTD 🩺 @MTDMED]

🩺 Ebstein Anomaly

A congenital malformation characterized by apical displacement of the tricuspid valve leaflets (especially the septal leaflet) into the right ventricle.

Pathophysiology

Part of the right ventricle becomes "atrialized"
Leads to severe tricuspid regurgitation
Enlarged right atrium
Reduced functional right ventricular size

Clinical features

Cyanosis
Dyspnea and exercise intolerance
Signs of right-sided heart failure
Palpitations and arrhythmias

Classic association

Maternal lithium exposure during pregnancy

ECG findings

Right atrial enlargement
Right bundle branch block
Pre-excitation/WPW syndrome is common

Chest X-ray

Marked cardiomegaly with a box-shaped (wall-to-wall) heart

Associated defects

Atrial septal defect (ASD)
Patent foramen ovale (PFO)

Echocardiography

Demonstrates apical displacement of the tricuspid valve and tricuspid regurgitation

Pearl
Think: Maternal lithium use + tricuspid valve displaced downward into the right ventricle + WPW syndrome + box-shaped heart = Ebstein anomaly.

[MTD 🩺 @MTDMED]

Patient’s mother had bipolar disorder.

What diagnosis comes to your mind first?

[MTD 🩺 @MTDMED]

🩺 Hyperdontia

Hyperdontia is the presence of supernumerary (extra) teeth beyond the normal dental complement.

Common types

Mesiodens (most common): extra tooth between the maxillary central incisors
Paramolars
Distomolars ("fourth molars")

Clinical features

Delayed eruption of permanent teeth
Crowding or malocclusion
Diastema
Impaction of adjacent teeth
Often discovered incidentally on dental radiographs

Associations

Cleidocranial dysplasia
Gardner syndrome
Cleft lip and palate

Management

Observation if asymptomatic
Extraction when causing eruption disturbances, crowding, or orthodontic problems

Pearl
The classic exam association for multiple supernumerary teeth is cleidocranial dysplasia, which also features delayed closure of cranial sutures and hypoplastic or absent clavicles.

[MTD 🩺 @MTDMED]

Spot diagnosis? 🚨

[MTD 🩺 @MTDMED]

🩺 Iris Freckles

Iris freckles are small, flat, pigmented spots on the anterior surface of the iris caused by increased melanin within iris melanocytes.

Key features

Flat, discrete, brown pigmented lesions
Usually multiple
Do not distort the iris architecture
Generally benign and asymptomatic
More common in individuals with lighter-colored irides

Clinical significance

Usually require no treatment
May be associated with increased ultraviolet light exposure
Important to distinguish from iris nevi, which are deeper stromal lesions and may cause localized iris distortion

Differential diagnosis

Iris nevus → Stromal lesion, often larger and deeper
Lisch nodules → Multiple dome-shaped melanocytic hamartomas seen in Neurofibromatosis type 1
Iris melanoma → Enlarging pigmented mass with potential for glaucoma, corectopia, or ectropion uveae

Pearl
Iris freckles are superficial and flat; iris nevi are deeper and may distort the iris stroma.

[MTD 🩺 @MTDMED]

What's the diagnosis?

[MTD 🩺 @MTDMED]

🩺 Limbal Dermoid

A limbal dermoid is a congenital benign choristoma (normal tissue in an abnormal location) found at the corneoscleral limbus, usually in the inferotemporal quadrant.

Key features

Present at birth
Well-circumscribed, yellow-white, elevated mass at the limbus
May contain hair follicles, sebaceous glands, and connective tissue
Usually unilateral
Can induce astigmatism and lead to amblyopia if large

Associations

Goldenhar syndrome (classic association)Hemifacial microsomia
Preauricular skin tags
Vertebral anomalies

Management
Observation if small and asymptomatic
Surgical excision if:Visually significant
Causing severe astigmatism
Cosmetic concern

Pearl
A limbal dermoid is a choristoma, whereas a dermoid cyst elsewhere is often considered a type of benign cystic teratoma-like lesion. In ophthalmology questions, a limbal dermoid should immediately suggest Goldenhar syndrome.

[MTD 🩺 @MTDMED]

"Hair growing out of the patient's eye"

What's the most likely diagnosis?

[MTD 🩺 @MTDMED]

🩺 Answer: C. Intussusception

The target sign (or doughnut sign) on abdominal ultrasound is the classic imaging finding of intussusception, where one segment of bowel telescopes into another.

Why?

On transverse ultrasound, the telescoped bowel creates concentric hypoechoic and hyperechoic rings, producing the characteristic target/bull's-eye appearance.
Most commonly occurs in infants and young children.
Presents with:Intermittent colicky abdominal pain
Vomiting
"Currant jelly" stools (late finding)
Palpable sausage-shaped abdominal mass

Why the others are wrong?
A. Appendicitis → Enlarged non-compressible appendix (>6 mm), not the classic target sign in abdominal ultrasound questions.
B. Volvulus → More associated with the whirlpool sign of twisted mesenteric vessels.
D. Ascites → Free fluid in the peritoneal cavity.

E. Ileus → Diffusely dilated bowel loops without the target appearance.

🎯 Target sign = Intussusception.

[MTD 🩺 @MTDMED]

Ultrasound of the abdomen showing a target sign suggests? 🎯

A. Appendicitis
B. Volvulus
C. Intussusception
D. Ascites
E. Ileus