Differential Diagnosis for the 18-month-old Boy
Single most likely diagnosis
- B) Congestive heart failure: The patient's symptoms of increasingly rapid breathing (tachypnea), irritability, and the physical examination findings of cardiomegaly on chest X-ray, along with ECG changes (right-axis deviation, left ventricular hypertrophy, and ST-segment depression), strongly suggest congestive heart failure as the most likely cause of his tachypnea. The recent history of a high-grade fever, "pink eye," red swollen hands, enlarged lymph nodes, and cracked red lips, which resolved spontaneously, could be indicative of Kawasaki disease, a condition known to cause cardiac complications including coronary artery aneurysms and subsequent heart failure.
Other Likely diagnoses
- D) Pericardial effusion: Although less likely than congestive heart failure given the provided information, pericardial effusion could be a consideration, especially if there's a suspicion of an autoimmune or infectious process affecting the heart. However, the absence of specific findings like a pericardial friction rub or significant respiratory distress out of proportion to cardiomegaly makes this less likely.
- E) Thickened internal layer of pulmonary arterioles: This could be related to pulmonary hypertension, which might be secondary to the cardiac issues suggested by the patient's history and examination findings. However, this would be more of a contributing factor rather than the primary cause of tachypnea in this context.
Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- C) Mitral valve obstruction: Although not directly suggested by the information provided, any form of valvular heart disease could lead to congestive heart failure and should be considered, especially in the context of a recent illness that could have cardiac involvement.
- A) Chronic inflammatory interstitial lung disease: This is less likely given the acute presentation and the specific cardiac findings, but it's a condition that could cause tachypnea and should be considered if other explanations are ruled out.
Rare diagnoses
- Other rare cardiac or pulmonary conditions could potentially explain this patient's presentation, including but not limited to cardiac tumors, congenital heart defects not previously diagnosed, or rare pulmonary diseases. However, these would be less likely given the information provided and the context of recent symptoms suggestive of Kawasaki disease or a similar condition leading to cardiac complications.