A 46-year-old woman presents to your medical office complaining of ‘feeling tired’. The patient states that she has been having some trouble eating because her ‘tongue hurts’, but she has no other complaints. On examination, the patient has pale conjunctiva and skin and also appears tired. She has a smooth, red tongue that is tender to touch with a tongue depressor. The patient’s hands and feet feel cold. Fluoroscopic evaluation of the swallowing mechanism and esophagus is normal. Which of the following diagnoses is most likely?

Herpes simplex virus-1 infection

A 5-year-old boy is brought to the emergency department for evaluation of a progressive rash that started 2 days ago. The rash began on the face and progressed to the trunk and extremities. Over the past week, he has had a runny nose, a cough, and red, crusty eyes. He immigrated with his family from Turkey 3 months ago. His father and his older brother have Behcet disease. Immunization records are unavailable. The patient appears irritable and cries during the examination. His temperature is 40.0°C (104°F). Examination shows general lymphadenopathy and dry mucous membranes. Skin turgor is decreased. There is a blanching, partially confluent erythematous maculopapular exanthema. Examination of the oral cavity shows small white spots with erythematous halos on the buccal mucosa. His hemoglobin concentration is 11.5 g/dL, leukocyte count is 6,000/mm3, and platelet count is 215,000/mm3. Serology confirms the diagnosis. Which of the following is the most appropriate next step in management?

Reassurance and follow-up in 3 days

Intravenous immunoglobulin (IVIG)

A 13-month-old girl is brought to the physician because of a pruritic rash for 2 days. The girl's mother says she noticed a few isolated skin lesions on her trunk two days ago that appear to be itching. The girl received her routine immunizations 18 days ago. Her mother has been giving her ibuprofen for her symptoms. The patient has no known sick contacts. She is at the 71st percentile for height and the 64th percentile for weight. She is in no acute distress. Her temperature is 38.1°C (100.6°F), pulse is 120/min, and respirations are 26/min. Examination shows a few maculopapular and pustular lesions distributed over the face and trunk. There are some excoriation marks and crusted lesions as well. Which of the following is the most likely explanation for these findings?

Replication of the attenuated vaccine strain

Antigen contact with presensitized T-lymphocytes

Reactivation of virus dormant in dorsal root ganglion

Immune complex formation and deposition

Crosslinking of preformed IgE antibodies

A 2-year-old girl presents with a rash on her body. Patient’s mother says she noticed the rash onset about 5 hours ago. For the previous 3 days, she says the patient has had a high fever of 39.0°C (102.2°F). Today the fever abruptly subsided but the rash appeared. Vitals are temperature 37.0°C (98.6°F), blood pressure 95/55 mm Hg, pulse 110/min, respiratory rate 30/min, and oxygen saturation 99% on room air. Physical examination reveals a maculopapular, non-confluent, blanchable rash on her back, abdomen, and chest extending superiorly towards the nape of the patient’s neck. Which of the following is this patient’s most likely diagnosis?

Erythema infectiosum (fifth disease)

A 4-year-old boy is brought to the pediatrician with fever, diarrhea and bilateral red eye for 7 days. His parents noted that he has never had an episode of diarrhea this prolonged, but several other children at daycare had been ill. His immunization history is up to date. His vitals are normal except for a temperature of 37.5°C (99°F). A physical exam is significant for mild dehydration, preauricular adenopathy, and bilateral conjunctival injection with watery discharge. What is the most likely diagnosis?

Vibrio parahaemolyticus infection

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?

Lower gastrointestinal hemorrhage

Acute disseminated encephalomyelitis (ADEM)

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?

Staphylococcal scalded skin syndrome

Diagnostic criteria and clinical features for USMLE Step 1: High-Yield Pediatrics Lessons

Kawasaki Disease - The Fiery Vasculitis

Acute febrile vasculitis of medium-sized arteries, primarily affecting children < 5 years. Major risk of coronary artery aneurysms.

Diagnostic Criteria: Fever for ≥ 5 days PLUS ≥ 4 of the following clinical features.

📌 Mnemonic: CRASH & Burn (Fever)

Conjunctivitis: Bilateral, non-exudative, limbic-sparing.
Rash: Polymorphous, generalized.
Adenopathy: Cervical, usually unilateral, ≥ 1.5 cm.
Strawberry tongue, lip erythema, cracking.
Hand/foot changes: Erythema, edema, and later, periungual desquamation.

Kawasaki Disease: Diagnostic Criteria

⭐ The most feared complication is coronary artery aneurysm. An echocardiogram is mandatory in all suspected cases to detect abnormalities.

Diagnostic Criteria - CRASH & BURN

📌 Mnemonic: CRASH & BURN

Principal criterion: BURN - Fever for ≥ 5 days, high-grade & remittent.

Diagnosis requires fever plus ≥ 4 of the following clinical features:

Conjunctivitis: Bilateral, non-purulent, limbic-sparing.
Rash: Polymorphous, maculopapular rash. Typically truncal.
Adenopathy: Cervical lymphadenopathy, usually unilateral, firm, non-suppurative, >1.5 cm.
Strawberry tongue & oral changes:
- Erythema, fissuring, and crusting of lips.
- Diffuse oropharyngeal erythema.
- "Strawberry tongue" with prominent papillae.
Hand & foot changes (peripheral extremities):
- Acute: Erythema and edema of palms and soles.
- Subacute: Periungual desquamation (peeling).

Kawasaki Disease: CRASH + BURN mnemonic

⭐ Exam Favourite: In cases of suspected incomplete Kawasaki disease (fever + 2-3 criteria), an echocardiogram is mandatory to check for coronary artery aneurysms, the most feared complication.

Clinical Phases - A Fever's Journey

Describes the typical progression of Kawasaki Disease over several weeks, crucial for anticipating complications.

Acute Phase (Weeks 1-2)
- Abrupt onset of high-grade fever > 38.5°C lasting > 5 days.
- Presence of principal clinical signs (CRASH criteria).
- High irritability.
- Myocarditis and pericarditis can occur.
Subacute Phase (Weeks 2-4)
- Fever and rash subside.
- Marked by thrombocytosis (platelet count ↑) and desquamation of fingers/toes.
- Arthritis and arthralgia may persist.
⭐ This phase carries the highest risk for developing coronary artery aneurysms.
Convalescent Phase (Months 1-3)
- Begins when all clinical signs have disappeared.
- Continues until ESR returns to normal.
- Beau's lines (transverse nail grooves) may appear.

High‑Yield Points - ⚡ Biggest Takeaways

Kawasaki Disease is a medium-vessel vasculitis primarily affecting children < 5 years.

Diagnosis requires fever ≥ 5 days plus ≥ 4 of the 5 principal clinical features (CRASH).

Key features include bilateral non-exudative conjunctivitis, polymorphous rash, cervical lymphadenopathy, oral mucosal changes (strawberry tongue), and extremity changes.

The most feared complication is coronary artery aneurysms, leading to long-term cardiac issues.

Treatment involves IVIG and high-dose aspirin to reduce inflammation and prevent aneurysms.

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