INI-CET 2026 - Internal Medicine Practice Questions

Q: The given disorders are associated with dystonia and basal ganglia involvement. Which one requires a fundamentally different treatment approach than the others?

Wilson disease. ***Wilson disease*** - This is a disorder of **copper metabolism** caused by mutations in the **ATP7B gene**, leading to accumulation of copper in the liver and basal ganglia. - The treatment is fundamentally different from the others, requiring **chelating agents** (e.g., penicillamine, trientine) or **zinc therapy** to lower copper levels, rather than focusing solely on symptom management for dystonia. *PKAN (Pantothenate kinase-associated neurodegeneration)* - This is a type of **NBIA (Neurodegeneration with Brain Iron Accumulation)** disorder caused by PANK2 gene mutations. - Treatment is primarily supportive; while **pantothenate supplementation** or iron chelation (like deferiprone) are sometimes investigated, they do not reverse the metabolic defect as definitively as specific therapy does in Wilson disease. *PLAN (PLA2G6-associated neurodegeneration)* - Also classified under **NBIA disorders**, characterized by dystonia, parkinsonism, and cognitive decline. - As with other neurodegenerative storage disorders, there is no curative, disease-altering therapy; management is purely **symptomatic** (e.g., baclofen, botulinum toxin for dystonia). *Dopa-responsive dystonia* - Caused by a defect in **dopamine synthesis** (typically GCH1 mutation), it is characterized by diurnal fluctuation of symptoms. - It is unique because it shows a dramatic and sustained response to **low-dose levodopa/carbidopa**, which serves as both the diagnostic test and the definitive treatment.

Q: What causes the resting tremors in Parkinson's disease?

Excitation of globus interna. ***Excitation of globus interna*** - In **Parkinson's disease**, the loss of dopaminergic neurons in the **substantia nigra pars compacta** removes the inhibitory influence on the **indirect pathway**. - This leads to increased activity of the subthalamic nucleus, which subsequently results in excessive **excitation of the globus pallidus internus (GPi)**, contributing to the characteristic parkinsonian tremor. *Loss of inhibition of globus externa* - The **globus pallidus externus (GPe)** is normally inhibited by the **striatum** via dopamine-D2 receptors. - While pathology in Parkinson's affects the entire basal ganglia circuit, the specific driver of the resting tremor is the excessive output from the GPi, not a primary failure of GPe inhibition. *Loss of inhibition of globus interna* - This describes a state that would actually reduce the output of the **basal ganglia**, potentially leading to hyperkinetic movements rather than the hypokinetic state seen in Parkinson's. - The GPi is the main **output nucleus** of the basal ganglia, and in Parkinson's, its activity is pathologically increased, not decreased. *Excitation of globus externa* - The **globus pallidus externus** is typically inhibited rather than excited in the pathological circuit of Parkinson's disease due to overactivity of the indirect pathway. - Increased activity of the GPe would inhibit the **subthalamic nucleus**, which contradicts the mechanism of increased GPi output that drives tremor and bradykinesia.

Q: A 25-year-old college student presents with progressive headache, vomiting, and double vision. Examination reveals bilateral 6th nerve palsy and papilledema. CT brain shows hydrocephalus. CSF analysis reveals lymphocytic dominance, markedly low glucose, and elevated protein. What is the most likely diagnosis?

Tubercular meningitis. ***Tubercular meningitis*** - The classic CSF triad of **lymphocytic pleocytosis**, **markedly low glucose (hypoglycorrhachia)**, and **elevated protein** is highly characteristic of tuberculous meningitis. - The presentation of **hydrocephalus** and **cranial nerve palsies (like CN VI palsy)** is a hallmark complication caused by the thick, gelatinous **basilar exudates** associated with this condition. *Viral meningitis* - Typically presents with **normal glucose levels** in the CSF and generally does not cause profound hydrocephalus or cranial nerve palsies. - This condition is often self-limiting, whereas the progression of symptoms here suggests a more chronic, invasive process. *Fungal meningitis* - While fungal infections like *Cryptococcus* can cause lymphocytic meningitis and high intracranial pressure, the classic profile strongly pointing to TB is the profound glucose consumption and typical basilar inflammation. - Cryptococcal meningitis is more commonly seen in heavily **immunocompromised patients (e.g., AIDS)**, and diagnostic testing for cryptococcal antigen would be the first line of investigation. *Bacterial meningitis* - Typically exhibits **neutrophilic predominance** in the CSF, rather than the lymphocytic dominance described in this case. - CSF glucose levels in typical bacterial meningitis are usually low, but the clinical course is generally **acute and fulminant** (hours to days), unlike the subacute progression often seen in tuberculosis.

Q: A 28-year-old woman with severe anorexia is admitted for nutritional rehabilitation. Within 48 hours of initiating enteral feeding, she develops muscle weakness, cardiac arrhythmias, and respiratory distress. Which metabolic abnormality is most characteristically responsible?

Hypophosphatemia. ***Hypophosphatemia*** - This patient is presenting with classic signs of **refeeding syndrome**, which occurs when rapid insulin secretion after carbohydrate ingestion triggers intracellular uptake of electrolytes, depleting serum pools. - **Hypophosphatemia** is the hallmark metabolic abnormality, leading to **adenosine triphosphate (ATP) depletion** and subsequent muscle weakness, cardiomyopathy, arrhythmias, and respiratory failure due to diaphragmatic weakness. *Hyponatremia* - While electrolyte disturbances are common in anorexia, **hyponatremia** is typically associated with excessive water intake or volume depletion rather than the rapid physiological shift seen in refeeding. - It does not explain the specific constellation of profound muscular and respiratory failure seen shortly after the initiation of feeding in this clinical context. *Hypocalcemia* - Although **hypocalcemia** can occur in refeeding syndrome due to an influx into the intracellular space, it is usually secondary and less frequently the primary cause of the severe, acute respiratory and cardiac symptoms described. - It typically manifests with signs of **tetany**, **Chvostek's sign**, or **Trousseau's sign** rather than the primary respiratory distress pattern seen here. *Hyperkalemia* - In the context of refeeding, the risk is typically **hypokalemia** due to the insulin-stimulated shift of potassium into cells, not hyperkalemia. - **Hyperkalemia** would likely present with different ECG changes, such as peaked T-waves, which is contrary to the clinical presentation of refeeding syndrome.

Q: A 15-year-old boy presents with hypertension and salt-water retention. He is suspected to have 17-alpha hydroxylase deficiency. What is the expected serological profile?

High mineralocorticoid, low cortisol, low androgen. ***High mineralocorticoid, low cortisol, low androgen*** - In **17-alpha hydroxylase deficiency**, the conversion of pregnenolone and progesterone to 17-OH derivatives (cortisol precursors) is blocked, which shunts the substrate toward the **mineralocorticoid pathway**. - This leads to excessive production of **deoxycorticosterone** (a potent mineralocorticoid), causing hypertension and salt retention, while simultaneously causing **cortisol** and **androgen** deficiency due to downstream blockages. *High mineralocorticoid, high cortisol, high androgen* - This profile is not seen in 17-alpha hydroxylase deficiency; **high androgens** are typically seen in 21-hydroxylase deficiency (congenital adrenal hyperplasia). - High cortisol would contradict the block in the glucocorticoid synthesis pathway caused by the enzyme deficiency. *High mineralocorticoid, high cortisol, low androgen* - While the mineralocorticoid levels are correctly described as high, **cortisol** levels are typically low due to the enzymatic block. - The deficiency of cortisol leads to increased **ACTH** (adrenocorticotropic hormone) secretion via feedback, but the enzyme block prevents downstream cortisol production. *Low mineralocorticoid, low cortisol, low androgen* - This profile is more characteristic of **Addison's disease** (primary adrenal insufficiency) where total adrenal function is impaired. - In 17-alpha hydroxylase deficiency, the mineralocorticoid pathway is essentially hyperactive, so low mineralocorticoid is incorrect.

Q: A 10-year-old boy presents with excessive eating (hyperphagia) and obesity, with a BMI of 33. Genetic testing shows a deletion on chromosome 15. What is the most likely diagnosis?

Prader-Willi syndrome. ***Prader-Willi syndrome*** - This condition is caused by a **paternal deletion** of the **15q11-q13** region or **maternal uniparental disomy**, which is consistent with the described genetic finding. - The classic clinical presentation includes **hyperphagia**, leading to severe **obesity**, alongside **intellectual disability**, almond-shaped eyes, and hypogonadism. *Angelman syndrome* - While also involving the **15q11-q13** region, this is caused by a **maternal deletion** or **paternal uniparental disomy**. - Clinically, patients present with a **happy demeanor**, frequent laughter, ataxia, and seizures, rather than hyperphagia and obesity. *Rett syndrome* - An **X-linked dominant** disorder caused by mutations in the **MECP2 gene**, typically affecting females due to male lethality. - Characterized by the **loss of purposeful hand movements**, developmental regression, and **stereotypical hand-wringing** behaviors. *Down syndrome* - Caused by **trisomy 21**, not a deletion on chromosome 15. - Features include **distinctive facial dysmorphology**, such as **epicanthic folds** and a flat nasal bridge, along with congenital heart defects and varying degrees of intellectual impairment.

Q: A 66-year-old female has normal calcium, elevated PTH, low phosphate, and raised ALP. What is the diagnosis?

Vitamin D deficiency. ***Vitamin D deficiency*** - In early or mild **Vitamin D deficiency**, the **parathyroid hormone (PTH)** is elevated (secondary hyperparathyroidism) to compensate for low calcium absorption, which often keeps serum **calcium** levels within the low-normal range. - The elevated **PTH** causes increased renal phosphate excretion (leading to **low phosphate**) and increased bone turnover (leading to **raised ALP**). *Primary hyperparathyroidism* - Typically characterized by **hypercalcemia** alongside elevated **PTH**, unlike the normal calcium seen here. - While elevated **ALP** and low **phosphate** can occur, the calcium profile is the primary differentiator. *Hypoparathyroidism* - Characterized by **low PTH** levels and **hypocalcemia**, which directly contradicts the lab findings presented. - It is usually due to surgical damage to the glands or autoimmune destruction, not a metabolic state of compensation. *Chronic kidney disease* - Often presents with **hyperphosphatemia** (high phosphate) due to impaired renal excretion, not the low phosphate seen in this patient. - While secondary hyperparathyroidism can occur, the typical profile is **low/normal calcium**, **high phosphate**, and **high PTH**.

Question 1

The given disorders are associated with dystonia and basal ganglia involvement. Which one
requires a fundamentally different treatment approach than the others?

Accepted Answer

Wilson disease

Answer

PKAN (Pantothenate kinase-associated neurodegeneration)

Answer

PLAN (PLA2G6-associated neurodegeneration)

Answer

Dopa-responsive dystonia

Question 2

What causes the resting tremors in Parkinson's disease?

Accepted Answer

Excitation of globus interna

Answer

Loss of inhibition of globus externa

Answer

Loss of inhibition of globus interna

Answer

Excitation of globus externa

Question 3

A 25-year-old college student presents with progressive headache, vomiting, and double vision.
Examination reveals bilateral 6th nerve palsy and papilledema. CT brain shows hydrocephalus. CSF
analysis reveals lymphocytic dominance, markedly low glucose, and elevated protein. What is the
most likely diagnosis?

Accepted Answer

Tubercular meningitis

Answer

Viral meningitis

Answer

Fungal meningitis

Answer

Bacterial meningitis

Question 4

A 28-year-old woman with severe anorexia is admitted for nutritional rehabilitation. Within 48
hours of initiating enteral feeding, she develops muscle weakness, cardiac arrhythmias, and
respiratory distress. Which metabolic abnormality is most characteristically responsible?

Accepted Answer

Hypophosphatemia

Answer

Hyponatremia

Answer

Hypocalcemia

Answer

Hyperkalemia

Question 5

A 15-year-old boy presents with hypertension and salt-water retention. He is suspected to have
17-alpha hydroxylase deficiency. What is the expected serological profile?

Accepted Answer

High mineralocorticoid, low cortisol, low androgen

Answer

High mineralocorticoid, high cortisol, high androgen

Answer

High mineralocorticoid, high cortisol, low androgen

Answer

Low mineralocorticoid, low cortisol, low androgen

Question 6

A 10-year-old boy presents with excessive eating (hyperphagia) and obesity, with a BMI of 33.
Genetic testing shows a deletion on chromosome 15. What is the most likely diagnosis?

Accepted Answer

Prader-Willi syndrome

Answer

Angelman syndrome

Answer

Rett syndrome

Answer

Down syndrome

Question 7

A 66-year-old female has normal calcium, elevated PTH, low phosphate, and raised ALP. What is
the diagnosis?

Accepted Answer

Vitamin D deficiency

Answer

Primary hyperparathyroidism

Answer

Hypoparathyroidism

Answer

Chronic kidney disease

INI-CET 2026 — Internal Medicine