Age-specific considerations US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Age-specific considerations. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Age-specific considerations US Medical PG Question 1: A 4-year-old boy is brought to the emergency department by his parents after 10 days of fever, varying from 38.0–40.0°C (100.4–104.0°F). On physical examination, the child is ill-looking with an extensive rash over his trunk with patchy desquamation. His hands are swollen, and he also shows signs of a bilateral conjunctivitis. The laboratory test results are as follows:
Hemoglobin 12.9 g/dL
Hematocrit 37.7%
Mean corpuscular volume 82.2 μm3
Leukocyte count 10,500/mm3
Neutrophils 65%
Lymphocytes 30%
Monocytes 5%
Platelet count 290,000/mm3
Erythrocyte sedimentation rate (ESR) 35 mm/h
What is the next best step in the management of this patient’s condition?
- A. High-dose aspirin (Correct Answer)
- B. Influenza vaccine
- C. Echocardiography
- D. Low-dose aspirin
- E. Corticosteroids
Age-specific considerations Explanation: ***High-dose aspirin***
- This patient presents with classic **Kawasaki disease**: prolonged fever (10 days), bilateral conjunctivitis, rash with desquamation, and extremity changes (swollen hands).
- Standard treatment for Kawasaki disease includes **IVIG (2 g/kg) plus high-dose aspirin (80-100 mg/kg/day)**. While both should be given together, **high-dose aspirin** is the best *therapeutic* option among those listed.
- High-dose aspirin provides anti-inflammatory effects during the acute phase and helps reduce fever and systemic inflammation.
- Treatment should be initiated promptly (ideally within 10 days of fever onset) to reduce the risk of **coronary artery aneurysms**.
*Influenza vaccine*
- The influenza vaccine is not a treatment for acute illness and has no role in managing Kawasaki disease.
- Vaccination would not address the ongoing systemic inflammation or prevent cardiac complications.
*Echocardiography*
- **Echocardiography should be performed** in all cases of Kawasaki disease to assess for coronary artery abnormalities, both at diagnosis and during follow-up.
- However, it is a **diagnostic/monitoring tool**, not a therapeutic intervention. Medical treatment to reduce inflammation takes priority over imaging.
- The question asks for the "next best step in management," which implies therapeutic action rather than diagnostic testing.
*Low-dose aspirin*
- Low-dose aspirin (3-5 mg/kg/day) is used during the **convalescent phase** for its antiplatelet effects, typically after fever resolution.
- It is transitioned to after the acute inflammatory phase is controlled with high-dose aspirin.
- Not appropriate for initial acute management where anti-inflammatory dosing is needed.
*Corticosteroids*
- Corticosteroids are reserved for **IVIG-refractory cases** or patients with severe coronary artery involvement.
- They are not part of initial first-line therapy and should not be used before IVIG administration.
- Their use is indicated only when standard therapy fails.
Age-specific considerations US Medical PG Question 2: A 4-year-old boy is brought to the emergency department by his mother with a rash on his trunk, malaise, and fever with spikes up to 38.5°C (101.3°F) for the past 2 weeks. The patient's mother says she tried giving him Tylenol with little improvement. Past medical history includes a spontaneous vaginal delivery at full term. The patient's vaccines are up-to-date and he has met all developmental milestones. On physical examination, his lips are cracking, and he has painful cervical lymphadenopathy. The rash is morbilliform and involves his trunk, palms, and the soles of his feet. There is fine desquamation of the skin of the perianal region. Which of the following anatomical structures is most important to screen for possible complications in this patient?
- A. Mitral valve
- B. Kidneys
- C. Gallbladder
- D. Coronary artery (Correct Answer)
- E. Pylorus
Age-specific considerations Explanation: ***Coronary artery***
- The constellation of symptoms, including prolonged fever, rash on trunk, palms, and soles, cracked lips, cervical lymphadenopathy, and perianal desquamation, is highly indicative of **Kawasaki disease**.
- **Coronary artery aneurysms** are the most serious complication of Kawasaki disease, occurring in 15-25% of untreated children, necessitating close monitoring and screening.
*Mitral valve*
- While other forms of vasculitis or rheumatic fever can affect heart valves, **mitral valve** involvement is not a primary or characteristic complication of Kawasaki disease.
- The main cardiac concern in Kawasaki disease is direct arterial inflammation, not valvular dysfunction.
*Kidneys*
- **Renal involvement**, such as acute kidney injury, is not a typical or prominent feature of Kawasaki disease.
- Kawasaki disease primarily targets medium-sized muscular arteries throughout the body, with a predilection for the coronary arteries.
*Gallbladder*
- **Hydrops of the gallbladder** can occur in Kawasaki disease, leading to acute cholecystitis-like symptoms, but it is generally a self-limiting complication.
- While it's a potential finding, it is not as life-threatening or essential to screen for as coronary artery complications.
*Pylorus*
- There is no direct association between Kawasaki disease and primary involvement or complications of the **pylorus**.
- Gastrointestinal symptoms can occur, but these are typically non-specific and do not involve anatomical changes to the pylorus.
Age-specific considerations US Medical PG Question 3: A 2-year-old boy is brought to the emergency department by his parents because of facial swelling that has now progressed to total body swelling. He also complains of nausea and abdominal pain. The child was in his usual state of health a week ago when they first notice swelling around his eyes. A few days later his legs started to swell. The boy was born at 39 weeks gestation via spontaneous vaginal delivery. He is up to date on all vaccines and is meeting all developmental milestones. Today, his blood pressure is 104/60 mm Hg, the heart rate is 90/min, the respiratory rate is 25/min, and the temperature is 37.1°C (98.8°F). On examination, he has facial edema, abdominal shifting dullness, and bilateral leg edema up to the knees. Urine dipstick shows 4+ protein and urinalysis shows fatty casts. Serum albumin is 2.2 g/dL. Which of the following is the most likely etiology of this patient condition?
- A. Acute glomerulonephritis
- B. Minimal change disease (Correct Answer)
- C. Congestive heart failure
- D. Kwashiorkor
- E. Protein-losing enteropathy
Age-specific considerations Explanation: ***Minimal change disease***
- This patient presents with **generalized edema**, **heavy proteinuria** (4+ protein with fatty casts), and **hypoalbuminemia** (< 2.5 g/dL), classic findings of **nephrotic syndrome**.
- **Minimal change disease** is the most common cause of nephrotic syndrome in children, typically presenting between 2 and 6 years of age, matching the patient's age and clinical picture.
*Acute glomerulonephritis*
- This condition is typically characterized by **hematuria**, **hypertension**, and **mild proteinuria**, often following a streptococcal infection.
- The patient's presentation with **massive proteinuria** and absence of hematuria or significant hypertension makes acute glomerulonephritis less likely.
*Congestive heart failure*
- While CHF can cause edema, it is usually accompanied by signs of **cardiac dysfunction** such as tachycardia, tachypnea, and an enlarged heart on imaging, which are not described.
- The primary cause of edema in CHF is **fluid overload** due to impaired cardiac output, not massive proteinuria and hypoalbuminemia as seen here.
*Kwashiorkor*
- This is a form of **severe protein malnutrition** leading to edema and abdominal distension, often seen in regions with food scarcity.
- The clinical context does not suggest malnutrition, and the presence of **heavy proteinuria** points to a renal pathology rather than a primary nutritional deficiency.
*Protein-losing enteropathy*
- This condition involves excessive protein loss through the **gastrointestinal tract**, leading to hypoalbuminemia and edema.
- However, it typically presents with **diarrhea** and malabsorption symptoms, which are not reported in this patient.
Age-specific considerations US Medical PG Question 4: A 9-month-old boy is brought to the physician because of increased irritability, continual crying, and fever for 1 day. His mother has noticed that he refuses to lie down on his right side and keeps tugging at his right ear. One week ago, he had a runny nose that has since improved. He was born at term and has been otherwise healthy. He was exclusively breastfed until 2 months of age and is currently bottle-fed with some solid foods introduced. He has been attending a daycare center for the past 5 months. His temperature is 38.4°C (101.1°F) and pulse is 144/min. Otoscopic examination in this child is most likely to show which of the following?
- A. Erythematous external auditory canal
- B. Vesicles in the ear canal
- C. Bulging erythematous tympanic membrane (Correct Answer)
- D. Brown mass within the ear canal
- E. Retracted opacified tympanic membrane
Age-specific considerations Explanation: ***Bulging erythematous tympanic membrane***
- The child's symptoms of **irritability**, **crying**, **fever**, **ear tugging**, and refusal to lie on one side, especially after a recent upper respiratory infection, are highly suggestive of **acute otitis media (AOM)**.
- In AOM, the **tympanic membrane (eardrum)** becomes inflamed, red (**erythematous**), and often **bulges** outwards due to the accumulation of fluid and pus in the middle ear.
*Erythematous external auditory canal*
- An **erythematous external auditory canal** is characteristic of **otitis externa** (swimmer's ear), which typically presents with pain upon manipulation of the tragus or pinna, and discharge, rather than the systemic symptoms like fever and irritability seen here.
- While some inflammation may extend to the external canal in AOM, the primary and most diagnostic finding for AOM is changes to the tympanic membrane itself.
*Vesicles in the ear canal*
- **Vesicles** in the ear canal or on the tympanic membrane, often accompanied by severe pain and possibly facial nerve palsy, are characteristic of **herpes zoster oticus** (Ramsay Hunt syndrome).
- This condition is caused by viral reactivation and does not fit the common presentation of fever, irritability, and ear tugging in an infant following a runny nose.
*Brown mass within the ear canal*
- A **brown mass** within the ear canal could indicate a cerumen impaction (earwax plug), a foreign body, or potentially a **cholesteatoma** (a benign skin growth that can erode bone).
- None of these conditions typically present with acute onset fever, irritability, and ear tugging in an infant, nor do they usually follow a recent upper respiratory infection.
*Retracted opacified tympanic membrane*
- A **retracted and opacified tympanic membrane** suggests changes in middle ear pressure, often seen in **eustachian tube dysfunction** or **otitis media with effusion (OME)**, where there is fluid but no acute infection.
- While OME can precede AOM, the presence of fever, acute irritability, and significant pain (implied by ear tugging and refusal to lie down) points strongly to an active, acute infection rather than just effusion or retraction.
Age-specific considerations US Medical PG Question 5: A 3-year-old boy is brought to the physician for evaluation of developmental delay. He could sit alone at 12 months and started walking with support at the age of 2 years. He can name only very few familiar objects and uses simple two-word sentences. He cannot stack more than 2 blocks. His parents report that he does not like playing with other children. He is at the 80th percentile for head circumference, 85th percentile for height, and 50th percentile for weight. He has a long and narrow face as well as large protruding ears. His thumbs can be passively flexed to the ipsilateral forearm. This patient is at increased risk of developing which of the following conditions?
- A. Mitral regurgitation (Correct Answer)
- B. Type 2 diabetes mellitus
- C. Acute myeloid leukemia
- D. Aortic dissection
- E. Hyperuricemia
Age-specific considerations Explanation: ***Mitral regurgitation***
- The patient's presentation with **developmental delay**, **relatively large head circumference** (80th percentile), **long narrow face**, **large protruding ears**, and **hyperextensible joints** (thumbs to forearm) is highly suggestive of **fragile X syndrome**.
- **Mitral valve prolapse** leading to **mitral regurgitation** is a common cardiac manifestation of fragile X syndrome, occurring in **50-80% of adult males** with the condition, due to **connective tissue dysplasia**.
*Type 2 diabetes mellitus*
- This condition is primarily associated with **obesity**, **insulin resistance**, and genetic predispositions unrelated to the features presented in this patient.
- While fragile X patients may have general health concerns, there is **no specific increased risk** of developing type 2 diabetes mellitus directly linked to the syndrome's pathology.
*Acute myeloid leukemia*
- There is **no established association** between fragile X syndrome and an increased risk of developing **acute myeloid leukemia**.
- AML is a **hematologic malignancy** with different risk factors, such as exposure to certain chemicals or prior chemotherapy.
*Aortic dissection*
- Aortic dissection is typically associated with conditions affecting **connective tissue** like **Marfan syndrome** or **Ehlers-Danlos syndrome**, or with **hypertension**.
- While fragile X syndrome involves connective tissue abnormalities, **aortic dissection is not a typical or significantly increased risk** compared to other connective tissue disorders.
*Hyperuricemia*
- **Hyperuricemia** is most commonly associated with conditions like **gout**, **kidney disease**, or certain **genetic metabolic disorders** (e.g., Lesch-Nyhan syndrome).
- There is **no direct link** between fragile X syndrome and an increased risk of hyperuricemia.
Age-specific considerations US Medical PG Question 6: A 6-month-old girl presents to an outpatient office for a routine physical. She can sit momentarily propped on her hands, babbles with consonants, and transfers objects hand to hand. The pediatrician assures the parents that their daughter has reached appropriate developmental milestones. Which additional milestone would be expected at this stage in development?
- A. Separation anxiety
- B. Showing an object to her parents to share her interest in that object
- C. Starts to share
- D. Engaging in pretend play
- E. Stranger anxiety (Correct Answer)
Age-specific considerations Explanation: ***Stranger anxiety***
- **Stranger anxiety** typically develops around **6–9 months** of age, peaking at **9–12 months**.
- This milestone aligns with the infant's increasing ability to distinguish familiar caregivers from unfamiliar individuals.
*Separation anxiety*
- **Separation anxiety** typically develops later, usually around **9–12 months** of age.
- It involves distress when a primary caregiver leaves, which is distinct from fear of strangers.
*Showing an object to her parents to share her interest in that object*
- **Joint attention**, where a child actively gestures or shows objects to share interest, typically emerges around **9–12 months**.
- This milestone requires more advanced social and cognitive development than expected at 6 months.
*Starts to share*
- The concept of **sharing** and reciprocal play develops later in toddlerhood, typically around **18 months to 2 years**.
- This involves understanding social give-and-take, which is too complex for a 6-month-old.
*Engaging in pretend play*
- **Pretend play** or symbolic play typically begins around **12–18 months** of age.
- It involves using objects or actions to represent something else and requires more advanced cognitive and imaginative skills.
Age-specific considerations US Medical PG Question 7: A 4-year-old boy is brought to the physician by his parents because of fever and mild abdominal pain for 7 days. His parents report that he developed a rash 2 days ago. He has had no diarrhea or vomiting. Four weeks ago, he returned from a camping trip to Colorado with his family. His immunization records are unavailable. His temperature is 39.4°C (102.9°F), pulse is 111/min, respirations are 27/min, and blood pressure is 96/65 mm Hg. Examination shows bilateral conjunctival injections and fissures on his lower lips. The pharynx is erythematous. There is tender cervical lymphadenopathy. The hands and feet appear edematous. A macular morbilliform rash is present over the trunk. Bilateral knee joints are swollen and tender; range of motion is limited by pain. Which of the following is the most appropriate treatment for this patient's condition?
- A. Supportive treatment only
- B. Intravenous immunoglobulin (Correct Answer)
- C. Oral ibuprofen
- D. Oral penicillin
- E. Oral doxycycline
Age-specific considerations Explanation: ***Intravenous immunoglobulin***
- This patient presents with symptoms highly suggestive of **Kawasaki disease**, including a persistent fever for over 5 days, **bilateral conjunctival injection**, **lip fissures**, **erythematous pharynx**, **cervical lymphadenopathy**, and **edema of hands and feet** followed by a rash.
- **IV immunoglobulin (IVIG)** is the cornerstone of treatment for Kawasaki disease, significantly reducing the risk of **coronary artery aneurysms** if given early in the disease course.
*Supportive treatment only*
- While supportive care (fever reduction, hydration) is important, relying solely on it for **Kawasaki disease** would increase the risk of severe complications, particularly **coronary artery involvement**.
- **Kawasaki disease** is a systemic vasculitis requiring specific immunomodulatory therapy to prevent long-term cardiac sequelae.
*Oral ibuprofen*
- **Ibuprofen**, a non-steroidal anti-inflammatory drug (**NSAID**), can help manage fever and joint pain, but it does not address the underlying **vasculitis** or prevent the cardiac complications of **Kawasaki disease**.
- **Aspirin** (high-dose initially, then low-dose) is part of Kawasaki disease treatment, but ibuprofen alone is insufficient as primary therapy.
*Oral penicillin*
- **Penicillin** is an antibiotic used to treat bacterial infections, such as **streptococcal pharyngitis**.
- This patient's symptoms are inconsistent with a typical bacterial infection requiring penicillin and are more indicative of a **systemic inflammatory condition** like Kawasaki disease, which is not bacterial.
*Oral doxycycline*
- **Doxycycline** is an antibiotic often used for **rickettsial infections** (e.g., Rocky Mountain spotted fever) or Lyme disease, which might be considered given the camping trip.
- However, the classic constellation of symptoms (conjunctival injection, lip changes, edema of extremities, diffuse rash) points strongly away from these and towards **Kawasaki disease**, for which doxycycline is ineffective.
Age-specific considerations US Medical PG Question 8: A 4-year-old boy is brought to a pediatrician by his parents with a history of fever for the last 5 days and irritability, decreased appetite, vomiting, and swelling of the hands and feet for the last 3 days. The patient’s mother mentions that he has been taking antibiotics and antipyretics prescribed by another physician for the last 3 days, but there has been no improvement His temperature is 39.4°C (103.0°F), pulse is 128/min, respiratory rate is 24/min, and blood pressure is 96/64 mm Hg. On physical examination, there is significant edema of the hands and feet bilaterally. There is a 2.5 cm diameter freely moveable, nontender cervical lymph node is palpable on the right side. A strawberry tongue and perianal erythema are noted. Conjunctival injection is present bilaterally. Laboratory findings reveal mild anemia and a leukocytosis with a left-shift. Erythrocyte sedimentation rate (ESR) and serum C-reactive protein (CRP) are increased. If not treated appropriately, this patient is at increased risk of developing which of the following complications?
- A. Lower gastrointestinal hemorrhage
- B. Coronary artery ectasia (Correct Answer)
- C. Acute renal failure
- D. Pulmonary embolism
- E. Acute disseminated encephalomyelitis (ADEM)
Age-specific considerations Explanation: ***Coronary artery ectasia***
- The patient's symptoms, including **prolonged fever**, **conjunctival injection**, **strawberry tongue**, **cervical lymphadenopathy**, **edema of hands and feet**, and **perianal erythema**, are characteristic of **Kawasaki disease**.
- If left untreated, **Kawasaki disease** can lead to significant cardiovascular complications, most notably **coronary artery aneurysms** or ectasia, due to vasculitis of medium-sized arteries.
*Lower gastrointestinal hemorrhage*
- While **gastrointestinal symptoms** such as vomiting and diarrhea can occur in **Kawasaki disease**, severe complications like **lower gastrointestinal hemorrhage** are rare and not the most common or critical untreated complication.
- Other conditions, like **Meckel's diverticulum** or **inflammatory bowel disease**, are more typically associated with lower GI hemorrhage in children.
*Acute renal failure*
- **Renal involvement** in **Kawasaki disease** is uncommon and usually presents as **mild proteinuria** or **sterile pyuria**; **acute renal failure** is an extremely rare complication.
- Significant renal dysfunction is more commonly seen in conditions like **hemolytic-uremic syndrome** or severe dehydration.
*Pulmonary embolism*
- **Pulmonary embolism** is rare in young children and not a typical complication of untreated **Kawasaki disease**.
- It is more commonly associated with conditions causing **hypercoagulability** or prolonged immobility.
*Acute disseminated encephalomyelitis (ADEM)*
- **ADEM** is an **immune-mediated demyelinating disorder** of the central nervous system that typically follows an infection or vaccination.
- It is not a recognized complication of untreated **Kawasaki disease**, whose primary pathology involves systemic vasculitis.
Age-specific considerations US Medical PG Question 9: A 5-year-old girl presents with a rash and a persistent fever of 41.0°C (105.8°F), not relieved by Tylenol. The patient's mother says that her symptoms started 5 days ago and have not improved. The rash started on her trunk and now is present everywhere including the palms and soles. Her birth history is normal. Her pulse is 120/min and respiratory rate is 22/min. On physical examination, the patient is agitated and ill-appearing. There is significant swelling of the distal upper and lower extremities bilaterally. The pharynx is hyperemic (see image). Generalized edema with palpable cervical lymphadenopathy is noted. Muscle tone is normal. Remainder of exam is unremarkable. Laboratory findings are significant for the following:
Laboratory test
Hb 9 g/dL
RBC 3.3/mm3
Neutrophilic leukocytosis 28,000/mm3
Normal platelet count 200,000/mm3
Serum ɣ-GT increased
Hyperbilirubinemia 2.98 mg/dL
AST and ALT are normal, but there is markedly increased serum CRP. Which of the following is the most likely diagnosis in this patient?
- A. Juvenile rheumatoid arthritis
- B. Scarlet fever
- C. Adenovirus infection
- D. Staphylococcal scalded skin syndrome
- E. Kawasaki disease (Correct Answer)
Age-specific considerations Explanation: ***Kawasaki disease***
- The constellation of **prolonged fever, rash (including palms and soles), swollen extremities, hyperemic pharynx, and cervical lymphadenopathy** in a young child is highly suggestive of **Kawasaki disease**.
- Laboratory findings such as **neutrophilic leukocytosis, elevated CRP, and increased γ-GT** further support this diagnosis, which is a **vasculitis** of medium-sized arteries.
*Juvenile rheumatoid arthritis*
- While juvenile rheumatoid arthritis (JRA) can cause **fever and joint swelling**, it typically does not present with the specific rash distribution, **hyperemic pharynx**, or **cervical lymphadenopathy** seen in this patient.
- The **acute onset and severity** of systemic symptoms are more characteristic of Kawasaki disease than typical JRA.
*Scarlet fever*
- Scarlet fever is caused by *Streptococcus pyogenes* and presents with a characteristic **sandpaper-like rash**, **strawberry tongue**, and **fever**.
- It does not typically cause **swelling of the extremities** or the specific laboratory abnormalities like **increased γ-GT** as seen here, and the rash of Kawasaki disease is often polymorphous rather than sandpaper-like.
*Adenovirus infection*
- Adenovirus infections can cause **fever, pharyngitis, and conjunctivitis**, but they do not typically lead to the characteristic widespread rash (including palms and soles), marked **extremity swelling**, or significantly elevated inflammatory markers observed in this case.
- The clinical picture presented is much more severe and specific for a systemic inflammatory condition.
*Staphylococcal scalded skin syndrome*
- **Staphylococcal scalded skin syndrome (SSSS)** is characterized by **erythema and superficial blistering/peeling of the skin**, giving a "scalded" appearance, often starting around the mouth.
- It does not typically cause the **hyperemic pharynx, swollen extremities, or cervical lymphadenopathy** described, and the rash in this patient is not described as blistering or peeling.
Age-specific considerations US Medical PG Question 10: A previously healthy 4-year-old boy is brought to the physician by his parents because he has had a fever, diffuse joint pain, and a rash on his abdomen for the past week. Acetaminophen did not improve his symptoms. He emigrated from China with his family 2 years ago. He attends daycare. His immunization records are not available. His temperature is 38.5°C (101.3°F), pulse is 125/min, and blood pressure is 100/60 mm Hg. Examination shows polymorphous truncal rash. The eyes are pink with no exudate. The tongue is shiny and red, and the lips are cracked. The hands and feet are red and swollen. There is right-sided anterior cervical lymphadenopathy. Which of the following is the most appropriate next step in management?
- A. HHV-6 immunoglobulin M (IgM) detection
- B. ANA measurement
- C. Echocardiography (Correct Answer)
- D. Monospot test
- E. Antistreptolysin O titer measurement
Age-specific considerations Explanation: ***Echocardiography***
- This patient presents with classic symptoms of **Kawasaki disease**, including protracted fever (>5 days), polymorphous rash, conjunctival injection, cracked lips and red tongue (**strawberry tongue**), swollen hands and feet, and cervical lymphadenopathy.
- The diagnosis can be made clinically when fever ≥5 days plus ≥4 of 5 principal criteria are present, which this patient meets.
- **Echocardiography** is essential to establish a **baseline cardiac assessment** and screen for **coronary artery aneurysms**, which occur in 15-25% of untreated patients.
- Among the diagnostic options listed, echocardiography is the most appropriate next step, though in clinical practice, **treatment with IVIG and high-dose aspirin should be initiated promptly** (ideally within 10 days of fever onset) and should not be delayed pending echocardiography results.
*HHV-6 immunoglobulin M (IgM) detection*
- **Human Herpesvirus 6 (HHV-6)** causes **roseola infantum** (exanthem subitum), which presents with high fever for 3-5 days followed by a rash that appears **as the fever resolves**.
- The mucocutaneous findings in this case (strawberry tongue, cracked lips, conjunctival injection, extremity swelling) are not consistent with roseola.
*ANA measurement*
- **Antinuclear antibody (ANA)** testing screens for **autoimmune diseases** such as systemic lupus erythematosus or juvenile idiopathic arthritis.
- While this patient has fever and joint pain, the specific mucocutaneous changes (strawberry tongue, cracked lips, conjunctival injection, polymorphous rash, extremity edema) and cervical lymphadenopathy are pathognomonic for Kawasaki disease, not typical autoimmune conditions.
*Monospot test*
- The **Monospot test** diagnoses **infectious mononucleosis** caused by **Epstein-Barr virus (EBV)**.
- While EBV can cause fever, rash, and lymphadenopathy (typically posterior cervical), the characteristic mucocutaneous findings of Kawasaki disease (strawberry tongue, cracked lips, conjunctival injection without exudate, extremity changes) are not seen in mononucleosis.
- Additionally, mononucleosis is uncommon in preschool-aged children.
*Antistreptolysin O titer measurement*
- **Antistreptolysin O (ASO) titer** detects recent **Group A Streptococcus** infection and can support a diagnosis of **acute rheumatic fever (ARF)**.
- ARF presents with migratory polyarthritis, carditis, and **erythema marginatum** (not a polymorphous rash), occurring 2-4 weeks after streptococcal pharyngitis.
- The mucocutaneous features in this case are specific to Kawasaki disease and not consistent with ARF.
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