A 53-year-old man is brought to the physician by his wife because of strange behavior and emotional outbursts for the past 6 months. He was previously healthy and physically active, but he recently started binge-eating candy and stopped exercising. He was fired from his job for inappropriate behavior after he undressed in the office and made lewd remarks to several female coworkers. He claims there is nothing wrong with his behavior. On mental status examination, he is alert and irritable but cooperative. Short-term recall is normal but he has some word-finding difficulties. Babinski reflex is positive bilaterally. This patient's symptoms are most likely due to a degenerative process in which of the following regions of the brain?
Q102
A parent-teacher conference is called to discuss the behavior of a 9 year-old boy. According to the boy's teacher, he has become progressively more disruptive during class. When asked to help clean up or read out-loud, he replies with "You're not the boss of me." or "You can't make me." He refuses to participate in gym class, but will play the same games during recess. He gets along with and is well-liked by his peers. His mother reports that her son can "sometimes be difficult," but he is helpful around the house and is very good playing with his 7-year-old sister. What is the most likely diagnosis?
Q103
A 25-year-old man presents to his primary care physician for trouble with focus and concentration. The patient states that he has lived at home with his parents his entire life but recently was able to get a job at a local factory. Ever since the patient has started working, he has had trouble focusing at his job. He is unable to stay focused on any task. His boss often observes him "daydreaming" with a blank stare off into space. His boss will have to yell at him to startle him back to work. The patient states that he feels fatigued all the time and sometimes will suddenly fall asleep while operating equipment. He has tried going to bed early for the past month but is unable to fall asleep until two hours prior to his alarm. The patient fears that if this continues he will lose his job. Which of the following is the best initial step in management?
Q104
A 9-year-old boy is brought to a psychologist by his mother because his teachers frequently complain about his behavioral problems at school. The patient’s mother reports that his concerning behavior started at a young age. She says he is disrespectful to family members and to his teachers at school. He also talks back to everyone. Grounding him and limiting his freedom has not improved his behavior. His grades have never been very good, and he is quite isolated at school. After a further review of the patient’s medical history and a thorough physical exam, the physician confirms the diagnosis of oppositional defiant disorder. Which of the following additional symptoms would most likely present in this patient?
Q105
A 13-year-old teenage girl was brought to the emergency department by her mom after she collapsed. Her mom reports that she was at a birthday party when all of a sudden she fell. She reported left foot weakness and has been limping ever since. The patient has been healthy and had an uncomplicated birth history, though her mom reports that she just recovered from a cold. She currently lives with her younger sister and mother as her parents recently divorced. She does well in school and has a handful of good friends. Her physical exam demonstrated normal bulk and tone, 5/5 strength in all motions, 2+ and symmetric reflexes at biceps, triceps and knees. She had 1+ ankle reflex on left. What is the most likely explanation for her symptoms?
Q106
A 28-year-old woman is brought into the clinic by her husband with concerns that she might be depressed. She delivered a healthy newborn a week and a half ago without any complications. Since then, she has been having trouble sleeping, eating poorly, and has stopped playing with the baby. The patient says she feels like she is drained all the time and feels guilty for not doing more for the baby. Which of the following is the best course of treatment for this patient?
Q107
A 23-year-old woman is seen by her primary care physician. The patient has a several year history of excessive daytime sleepiness. She also reports episodes where she suddenly falls to the floor after her knees become weak, often during a laughing spell. She has no other significant past medical history. Her primary care physician refers her for a sleep study, which confirms the suspected diagnosis. Which of the following laboratory findings would also be expected in this patient?
Q108
A 12-year-old boy is brought in by his parents as they are concerned about his behavior. He is constantly arguing with his parents and blatantly defying their every request. In school, he is known for being intentionally tardy and for defying his teachers. Upon further questioning of the patient you learn about some of his recent behaviors such as beginning smoking to bother his parents. You also notice that he is disrespectful towards you. You then learn that he has also gotten into weekly fights with his peers at school with no apparent cause. In addition, last week he was seen hitting one of the local neighborhood cats with a baseball bat trying to kill it. The patient lives at home with his two parents in a pre-World War II house that was recently renovated. Physical exam is unremarkable.
Laboratory values are as follows:
Na: 140 mmol/L
K: 4.5 mmol/L
Cl: 100 mmol/L
Glucose: 80 mg/dL
Ca: 10 mmol/L
Mg: 3 mEq/L
Cr: 0.8 mg/dL
BUN: 10 mg/dL
Serum lead: < .01 µg/dL
Hb: 15 g/dL
Hct: 45%
MCV: 95
Urine toxicology: negative
As the patient leaves the office you notice him stealing all of the candy from the office candy bowl. The patient seems unconcerned about his behavior overall. Which of the following statements is most likely to be true in this patient?
Q109
A 37-year-old patient is being evaluated for involuntary movements, difficulty swallowing food, and personality change. He has entered a clinical trial that is studying the interaction of certain neuromediators in patients with similar (CAG) n trinucleotide repeat disorders. The laboratory results of 1 of the candidates for the clinical trial are presented below:
Acetylcholine ↓
Dopamine ↑
Gamma-aminobutyric acid (GABA) ↓
Norepinephrine unchanged
Serotonin unchanged
Which trinucleotide disorder most likely represents the diagnosis of this patient?
Mood Disorders US Medical PG Practice Questions and MCQs
Question 101: A 53-year-old man is brought to the physician by his wife because of strange behavior and emotional outbursts for the past 6 months. He was previously healthy and physically active, but he recently started binge-eating candy and stopped exercising. He was fired from his job for inappropriate behavior after he undressed in the office and made lewd remarks to several female coworkers. He claims there is nothing wrong with his behavior. On mental status examination, he is alert and irritable but cooperative. Short-term recall is normal but he has some word-finding difficulties. Babinski reflex is positive bilaterally. This patient's symptoms are most likely due to a degenerative process in which of the following regions of the brain?
A. Frontal cortex (Correct Answer)
B. Corona radiata
C. Hippocampus
D. Caudate nucleus
E. Substantia nigra
Explanation: ***Frontal cortex***
- This patient's symptoms, including **behavioral disinhibition** (inappropriate sexual behavior, emotional outbursts, undressing in the office), **changes in eating habits** (binge-eating candy), **loss of empathy**, and **lack of insight**, are classic presentations of **frontotemporal dementia (FTD)**.
- **Word-finding difficulties** and the **positive Babinski reflex** bilaterally further support a neurodegenerative process affecting the **frontal lobes**, which are crucial for executive function, social conduct, and language.
*Corona radiata*
- The **corona radiata** consists of white matter tracts connecting the cerebral cortex to the brainstem and spinal cord.
- While damage here can cause motor and sensory deficits, it is **less directly involved in the primary behavioral and personality changes** seen in this patient compared to the frontal cortex.
*Hippocampus*
- The **hippocampus** is primarily involved in **memory formation**, particularly **short-term and declarative memory**.
- This patient's **short-term recall is normal**, making the hippocampus an unlikely primary site of degeneration for the presented symptoms.
*Caudate nucleus*
- The **caudate nucleus** is part of the **basal ganglia** and is involved in motor control, learning, and cognitive functions.
- While atrophy can occur in some neurodegenerative diseases like Huntington's disease, the predominant symptoms here are **behavioral and executive dysfunction**, not typical of isolated caudate pathology.
*Substantia nigra*
- The **substantia nigra** is a midbrain structure crucial for **motor control** due to its role in dopamine production.
- Degeneration of the substantia nigra is characteristic of **Parkinson's disease**, leading to bradykinesia, rigidity, and tremor, which are not the primary features described here.
Question 102: A parent-teacher conference is called to discuss the behavior of a 9 year-old boy. According to the boy's teacher, he has become progressively more disruptive during class. When asked to help clean up or read out-loud, he replies with "You're not the boss of me." or "You can't make me." He refuses to participate in gym class, but will play the same games during recess. He gets along with and is well-liked by his peers. His mother reports that her son can "sometimes be difficult," but he is helpful around the house and is very good playing with his 7-year-old sister. What is the most likely diagnosis?
A. Conduct disorder
B. Attention deficit disorder
C. Separation anxiety disorder
D. Oppositional defiant disorder (Correct Answer)
E. Antisocial personality disorder
Explanation: ***Oppositional defiant disorder***
- The boy exhibits a pattern of **defiant and disobedient behavior** towards authority figures (teacher) but a generally good relationship with peers and family, which is characteristic of ODD.
- His refusal to participate in formal class activities while still engaging in informal play highlights a specific defiance towards structured rules rather than a general aversion to activity.
*Conduct disorder*
- This disorder involves a more severe pattern of **aggression, destruction of property, deceitfulness, or serious rule violations**, which are not described in the boy's behavior.
- The boy's ability to get along with peers and be helpful at home suggests he does not meet the criteria for significant social impairment or callousness seen in conduct disorder.
*Attention deficit disorder*
- This disorder is characterized by **inattention, hyperactivity, and impulsivity**, which are not the primary symptoms described here.
- While defiance might be a secondary issue, the core problem is not difficulty sustaining attention or controlling impulsive behaviors.
*Separation anxiety disorder*
- This involves **excessive fear or anxiety concerning separation from home or attachment figures**, which is not indicated by any of the behavioral descriptions.
- The boy's issues are related to defiance and authority, not fear of separation.
*Antisocial personality disorder*
- This diagnosis can only be made in individuals **18 years or older** and requires a pervasive pattern of disregard for and violation of the rights of others.
- The boy's age (9 years old) and his reported positive relationships with peers and family rule out this diagnosis.
Question 103: A 25-year-old man presents to his primary care physician for trouble with focus and concentration. The patient states that he has lived at home with his parents his entire life but recently was able to get a job at a local factory. Ever since the patient has started working, he has had trouble focusing at his job. He is unable to stay focused on any task. His boss often observes him "daydreaming" with a blank stare off into space. His boss will have to yell at him to startle him back to work. The patient states that he feels fatigued all the time and sometimes will suddenly fall asleep while operating equipment. He has tried going to bed early for the past month but is unable to fall asleep until two hours prior to his alarm. The patient fears that if this continues he will lose his job. Which of the following is the best initial step in management?
A. Zolpidem
B. Ethosuximide
C. Modafinil
D. Polysomnography (Correct Answer)
E. Bright light therapy
Explanation: ***Polysomnography***
- The patient's symptoms of excessive daytime sleepiness, sudden sleep attacks (possibly **cataplexy**), and difficulty maintaining sleep, along with the "daydreaming" spells, are highly suggestive of **narcolepsy**.
- **Polysomnography** is the gold standard diagnostic test for narcolepsy and other sleep disorders, confirming the diagnosis and ruling out other causes of excessive somnolence.
*Zolpidem*
- **Zolpidem** is a sedative-hypnotic primarily used for treating **insomnia** by helping to initiate and maintain sleep.
- While the patient has difficulty falling asleep, addressing the underlying cause of his **excessive daytime sleepiness** is the priority before symptomatic treatment of insomnia.
*Ethosuximide*
- **Ethosuximide** is an anti-epileptic drug specifically used to treat **absence seizures** (petit mal seizures).
- Although the patient's "daydreaming" spells might resemble absence seizures, the combination with profound daytime sleepiness and sudden sleep attacks points away from epilepsy and towards a primary sleep disorder.
*Modafinil*
- **Modafinil** is a stimulant used to promote wakefulness in patients with excessive daytime sleepiness associated with narcolepsy, obstructive sleep apnea, and shift work sleep disorder.
- While it might be a potential treatment, it is usually initiated *after* a definitive diagnosis is established through **polysomnography** and other sleep studies.
*Bright light therapy*
- **Bright light therapy** is primarily used to treat **seasonal affective disorder** and **circadian rhythm sleep disorders**, such as delayed sleep phase syndrome.
- The patient's symptoms are more severe and complex than typical circadian rhythm issues and include sudden sleep attacks, making this an inappropriate initial intervention without a proper diagnosis.
Question 104: A 9-year-old boy is brought to a psychologist by his mother because his teachers frequently complain about his behavioral problems at school. The patient’s mother reports that his concerning behavior started at a young age. She says he is disrespectful to family members and to his teachers at school. He also talks back to everyone. Grounding him and limiting his freedom has not improved his behavior. His grades have never been very good, and he is quite isolated at school. After a further review of the patient’s medical history and a thorough physical exam, the physician confirms the diagnosis of oppositional defiant disorder. Which of the following additional symptoms would most likely present in this patient?
A. Fights at school
B. Staying out of home at nights despite restrictions
C. History of deliberately damaging furniture
D. Frequently leaving his seat during class despite instructions by the teacher
E. Blaming others for his own misbehavior (Correct Answer)
Explanation: ***Blaming others for his own misbehavior***
- **Oppositional Defiant Disorder (ODD)** is characterized by a pattern of angry/irritable mood, argumentative/defiant behavior, or vindictiveness, often including **blaming others for their mistakes or misbehavior**.
- The patient's established pattern of disrespect and talking back aligns with the argumentative and defiant nature of ODD, making blaming others a highly consistent additional symptom.
*Fights at school*
- While fighting can occur in children with ODD, **physical aggression is more characteristic of Conduct Disorder (CD)**.
- ODD primarily involves verbal defiance and non-compliance, not necessarily direct physical altercations.
*Staying out of home at nights despite restrictions*
- **Running away from home or staying out despite parental rules is a feature of Conduct Disorder (CD)**, not typically ODD.
- ODD is focused on defiance within established settings, whereas CD involves more severe violations of societal norms and rules.
*History of deliberately damaging furniture*
- **Deliberate destruction of property is a core symptom of Conduct Disorder (CD)**.
- ODD involves defiance and an irritable mood, but usually stops short of actively damaging property.
*Frequently leaving his seat during class despite instructions by the teacher*
- This symptom is more indicative of **Attention-Deficit/Hyperactivity Disorder (ADHD)**, specifically the hyperactive-impulsive presentation.
- While comorbidity with ODD is common, this specific behavior is not a defining characteristic of ODD itself.
Question 105: A 13-year-old teenage girl was brought to the emergency department by her mom after she collapsed. Her mom reports that she was at a birthday party when all of a sudden she fell. She reported left foot weakness and has been limping ever since. The patient has been healthy and had an uncomplicated birth history, though her mom reports that she just recovered from a cold. She currently lives with her younger sister and mother as her parents recently divorced. She does well in school and has a handful of good friends. Her physical exam demonstrated normal bulk and tone, 5/5 strength in all motions, 2+ and symmetric reflexes at biceps, triceps and knees. She had 1+ ankle reflex on left. What is the most likely explanation for her symptoms?
A. Guillain-Barre syndrome
B. Cerebral vascular accident
C. Conversion disorder (Correct Answer)
D. Multiple sclerosis
E. Myasthenia gravis
Explanation: ***Conversion disorder***
- The patient's presentation with acute onset of neurological symptoms (left foot weakness, limping) following a stressful event (parents' divorce) and a recent illness, coupled with a **neurological exam that is inconsistent with true organic disease** (reported weakness but 5/5 strength on exam), is highly suggestive of a **conversion disorder**.
- **Conversion disorder**, also known as **functional neurological symptom disorder**, involves neurological symptoms lacking a compatible neurological or medical explanation, often triggered by psychological stress.
*Guillain-Barre syndrome*
- This is an **acute demyelinating polyneuropathy** characterized by **ascending paralysis** and **areflexia**, typically following an infection.
- The physical exam findings of normal strength and only a slightly diminished ankle reflex on one side are not consistent with the widespread weakness and **loss of reflexes** seen in Guillain-Barré syndrome.
*Cerebral vascular accident*
- A stroke (**CVA**) in a 13-year-old girl is rare without predisposing factors and would typically present with more definitive and consistent neurological deficits, such as **hemiparesis**, **facial droop**, or **aphasia**, which are absent here.
- The neurological exam showing normal strength and tone throughout, despite reported weakness, does not align with the **focal neurological deficits** expected from a CVA.
*Multiple sclerosis*
- **Multiple sclerosis** is a demyelinating disease of the central nervous system that typically presents with fluctuating neurological symptoms over time, often involving **sensory disturbances**, **visual changes**, or **motor weakness**.
- While an acute onset is possible, the reported weakness with an otherwise normal neurological exam and the single, isolated symptom without other characteristic features make MS less likely.
*Myasthenia gravis*
- **Myasthenia gravis** is an autoimmune disorder characterized by **fluctuating muscle weakness** that **worsens with activity** and improves with rest, often affecting ocular, bulbar, and limb muscles.
- The patient's reported weakness being constant and her normal strength on examination, without the typical fluctuating fatigue or specific muscle group involvement, argues against myasthenia gravis.
Question 106: A 28-year-old woman is brought into the clinic by her husband with concerns that she might be depressed. She delivered a healthy newborn a week and a half ago without any complications. Since then, she has been having trouble sleeping, eating poorly, and has stopped playing with the baby. The patient says she feels like she is drained all the time and feels guilty for not doing more for the baby. Which of the following is the best course of treatment for this patient?
A. Reassurance
B. Fluoxetine (Correct Answer)
C. Risperidone
D. Amitriptyline
E. No treatment
Explanation: ***Fluoxetine***
- This patient's symptoms (trouble sleeping, poor appetite, guilt, and anhedonia towards the baby) occurring 10 days postpartum are highly suggestive of **postpartum depression**. **SSRIs** like fluoxetine are first-line pharmacological treatments for this condition.
- Fluoxetine is a **selective serotonin reuptake inhibitor (SSRI)** that helps regulate mood by increasing serotonin levels in the brain. It is generally considered safe during breastfeeding, with a relatively low infant exposure compared to other antidepressants.
*Reassurance*
- Reassurance alone may be appropriate for **postpartum blues**, which are milder and self-limiting, typically resolving within two weeks.
- This patient's symptoms are more severe and persistent, lasting beyond typical postpartum blues and significantly impacting her functioning, indicating a need for more substantial intervention.
*Risperidone*
- Risperidone is an **atypical antipsychotic** primarily used to treat conditions like schizophrenia or bipolar disorder, or as an adjunct for severe refractory depression with psychotic features.
- There is no indication of psychosis in this patient's presentation, and the use of an antipsychotic would be disproportionate and carry unnecessary side effects.
*Amitriptyline*
- Amitriptyline is a **tricyclic antidepressant (TCA)**. While effective for depression, TCAs are generally not first-line due to a less favorable side effect profile (e.g., anticholinergic effects, cardiac conductivity issues) compared to SSRIs.
- SSRIs like fluoxetine are preferred for initial treatment of postpartum depression due to their better tolerability and safety profile.
*No treatment*
- This patient exhibits clear symptoms of **postpartum depression**, which is a serious condition that can worsen without intervention and impact both the mother's and infant's well-being.
- Untreated depression can lead to significant functional impairment, chronic suffering, and in severe cases, harm to oneself or the baby.
Question 107: A 23-year-old woman is seen by her primary care physician. The patient has a several year history of excessive daytime sleepiness. She also reports episodes where she suddenly falls to the floor after her knees become weak, often during a laughing spell. She has no other significant past medical history. Her primary care physician refers her for a sleep study, which confirms the suspected diagnosis. Which of the following laboratory findings would also be expected in this patient?
A. Increased serum ESR
B. Undetectable CSF hypocretin-1 (Correct Answer)
C. Reduced serum hemoglobin
D. Increased serum methemoglobin
E. Increased CSF oligoclonal bands
Explanation: ***Undetectable CSF hypocretin-1***
- The patient's symptoms of excessive daytime sleepiness and **cataplexy** (suddenly falling after knees become weak during laughing spells) are classic for **narcolepsy with cataplexy**.
- **Narcolepsy with cataplexy** is associated with the destruction of **hypocretin-producing neurons** in the hypothalamus, leading to undetectable levels of **hypocretin-1 (orexin A)** in the cerebrospinal fluid.
*Increased serum ESR*
- An **elevated erythrocyte sedimentation rate (ESR)** is a non-specific marker of inflammation and is not typically associated with narcolepsy.
- Inflammatory conditions such as **autoimmune diseases** or **infections** would cause an increased ESR.
*Reduced serum hemoglobin*
- **Reduced serum hemoglobin** indicates **anemia**, which is not a characteristic finding in narcolepsy with cataplexy.
- Anemia can cause fatigue but does not explain the episodes of cataplexy.
*Increased serum methemoglobin*
- **Methemoglobin** is an abnormal form of hemoglobin, and its increase (methemoglobinemia) is typically caused by exposure to certain **drugs or toxins**, not narcolepsy.
- It would lead to **cyanosis** and reduced oxygen carrying capacity, unrelated to the patient's symptoms.
*Increased CSF oligoclonal bands*
- **Oligoclonal bands in CSF** are indicative of **intrathecal immunoglobulin production** and are a hallmark finding in **multiple sclerosis (MS)**.
- While MS can cause fatigue, the specific presentation of cataplexy and excessive daytime sleepiness points away from MS as the primary diagnosis.
Question 108: A 12-year-old boy is brought in by his parents as they are concerned about his behavior. He is constantly arguing with his parents and blatantly defying their every request. In school, he is known for being intentionally tardy and for defying his teachers. Upon further questioning of the patient you learn about some of his recent behaviors such as beginning smoking to bother his parents. You also notice that he is disrespectful towards you. You then learn that he has also gotten into weekly fights with his peers at school with no apparent cause. In addition, last week he was seen hitting one of the local neighborhood cats with a baseball bat trying to kill it. The patient lives at home with his two parents in a pre-World War II house that was recently renovated. Physical exam is unremarkable.
Laboratory values are as follows:
Na: 140 mmol/L
K: 4.5 mmol/L
Cl: 100 mmol/L
Glucose: 80 mg/dL
Ca: 10 mmol/L
Mg: 3 mEq/L
Cr: 0.8 mg/dL
BUN: 10 mg/dL
Serum lead: < .01 µg/dL
Hb: 15 g/dL
Hct: 45%
MCV: 95
Urine toxicology: negative
As the patient leaves the office you notice him stealing all of the candy from the office candy bowl. The patient seems unconcerned about his behavior overall. Which of the following statements is most likely to be true in this patient?
A. This patient will likely function normally despite continuing to defy authority figures
B. Environmental exposures are likely causing this patient's behavior
C. The patient's symptoms could progress to antisocial personality disorder (Correct Answer)
D. This patient is suffering from antisocial personality disorder and will likely be incarcerated in adulthood
E. Strong D2 antagonists are first-line pharmacotherapy
Explanation: ***The patient's symptoms could progress to antisocial personality disorder***
- The patient's pattern of **aggression towards people and animals**, **deceitfulness or theft**, and **serious violations of rules** (e.g., truancy, defying authority) are all diagnostic criteria for **conduct disorder**.
- If conduct disorder symptoms persist into adulthood (age 18 or older), it can lead to a diagnosis of **antisocial personality disorder (ASPD)**, as ASPD requires evidence of conduct disorder before age 15.
*This patient will likely function normally despite continuing to defy authority figures*
- The described behaviors go beyond simple defiance; they include **aggression, severe rule violations, and lack of remorse**. These are significant indicators of a **conduct disorder**, which is associated with poor long-term outcomes and functional impairment, not normal functioning.
- Undiagnosed and untreated conduct disorder can lead to **academic difficulties, substance abuse, legal problems, and inability to maintain relationships**, making normal functioning unlikely.
*Environmental exposures are likely causing this patient's behavior*
- While environmental factors can contribute, the **severity and widespread nature** of the behaviors (at home, school, with peers, and animals), coupled with the **lack of remorse and intentional malice**, point more strongly to an underlying psychiatric diagnosis like conduct disorder rather than solely environmental causes.
- The provided lab results rule out common environmental toxins like **lead poisoning**, and the recent house renovation doesn't provide direct evidence of a toxic exposure causing these specific behavioral manifestations.
*This patient is suffering from antisocial personality disorder and will likely be incarcerated in adulthood*
- **Antisocial personality disorder (ASPD)** cannot be diagnosed before age 18. This patient is 12 years old, making ASPD an incorrect diagnosis at this stage, although his current behaviors are consistent with **conduct disorder**, which is a precursor.
- While there is an increased risk of incarceration for individuals with ASPD, stating it as a **definitive outcome** or that he "will likely be incarcerated" is deterministic and not universally true, as interventions can impact outcomes.
*Strong D2 antagonists are first-line pharmacotherapy*
- **First-line treatment for conduct disorder** typically involves **psychosocial interventions**, such as parent management training, cognitive behavioral therapy, and multisystemic therapy.
- While **D2 antagonists** (antipsychotics) may be used in severe cases, particularly for **aggression and impulsivity** when other treatments fail or if there are comorbid conditions, they are not considered **first-line pharmacotherapy** for conduct disorder itself.
Question 109: A 37-year-old patient is being evaluated for involuntary movements, difficulty swallowing food, and personality change. He has entered a clinical trial that is studying the interaction of certain neuromediators in patients with similar (CAG) n trinucleotide repeat disorders. The laboratory results of 1 of the candidates for the clinical trial are presented below:
Acetylcholine ↓
Dopamine ↑
Gamma-aminobutyric acid (GABA) ↓
Norepinephrine unchanged
Serotonin unchanged
Which trinucleotide disorder most likely represents the diagnosis of this patient?
A. Huntington's disease (Correct Answer)
B. Fragile X syndrome
C. Spinobulbar muscular atrophy
D. Friedreich's ataxia
E. Myotonic dystrophy
Explanation: ***Huntington's disease***
- The constellation of **involuntary movements** (**chorea**), **dysphagia**, and **personality changes** is classic for Huntington's disease, a **neurodegenerative disorder**.
- The specific pattern of neurotransmitter changes—**decreased acetylcholine and GABA**, with **increased dopamine**—is characteristic of the basal ganglia dysfunction seen in Huntington's, caused by a **CAG trinucleotide repeat expansion** in the huntingtin gene.
*Fragile X syndrome*
- This is a common cause of **inherited intellectual disability**, typically presenting with **developmental delay**, **macro-orchidism**, and characteristic facial features.
- It is caused by a **CGG trinucleotide repeat expansion** in the FMR1 gene, not a CAG repeat, and does not typically present with the described motor and psychological symptoms or the specific neurotransmitter profile.
*Spinobulbar muscular atrophy*
- Also known as **Kennedy's disease**, this is an **X-linked recessive disorder** characterized by **progressive muscle weakness** and **atrophy**, especially in bulbar and limb muscles.
- It is caused by a **CAG trinucleotide repeat expansion** in the androgen receptor gene, but its clinical presentation primarily involves motor neuron dysfunction, not the prominent chorea and psychiatric features described.
*Friedreich's ataxia*
- This is an **autosomal recessive ataxia** characterized by progressive gait and limb **ataxia**, **dysarthria**, and often **scoliosis** and **cardiomyopathy**.
- It is caused by a **GAA trinucleotide repeat expansion** in the FXN gene, mainly affecting cerebellar and spinal cord tracts, and its clinical features and neurotransmitter profile differ from the patient's presentation.
*Myotonic dystrophy*
- This is an **autosomal dominant disorder** characterized by **myotonia** (delayed muscle relaxation), **progressive muscle weakness** and wasting, cataracts, and cardiac conduction abnormalities.
- It is caused by a **CTG trinucleotide repeat expansion** in the DMPK gene (Type 1) or a CCTG repeat (Type 2) and does not typically present with involuntary choreiform movements or the described specific neurotransmitter alterations.