Differential Diagnosis for 44-Day Infant with Edema, Hypoalbuminemia, Hypokalemia, and Hypocalcemia

Single Most Likely Diagnosis

• Congenital Nephrotic Syndrome of the Finnish Type (CNF): Although the urine protein/creatinine ratio is normal, CNF should be considered due to the infant's age and presentation. However, the normal urine protein/creatinine ratio makes this less likely than other conditions that directly cause hypoalbuminemia through non-renal mechanisms.

Other Likely Diagnoses

• Nutritional Deficiencies: Given the infant's young age, nutritional deficiencies could lead to hypoalbuminemia, hypokalemia, and hypocalcemia. Edema could be secondary to the hypoalbuminemia.
• Gastrointestinal Losses: Conditions like congenital diarrhea or intestinal lymphangiectasia could lead to loss of proteins, potassium, and calcium, resulting in the observed laboratory abnormalities.
• Liver Disease: Neonatal liver diseases (e.g., biliary atresia, neonatal hepatitis) can cause hypoalbuminemia and edema. Hypokalemia and hypocalcemia could be secondary to liver dysfunction affecting nutrient and electrolyte metabolism.

Do Not Miss Diagnoses

• Congenital Heart Disease with Cardiac Failure: Although less directly related to the specific lab abnormalities, cardiac failure can cause edema and indirectly affect liver and kidney function, leading to secondary electrolyte and protein imbalances.
• Inborn Errors of Metabolism: Certain metabolic disorders can present with electrolyte imbalances and edema. These conditions are critical to identify early due to the potential for severe outcomes if not promptly treated.

Rare Diagnoses

• Liddle Syndrome: A rare genetic disorder leading to excessive sodium absorption and potassium wasting in the kidneys, which could contribute to hypokalemia. However, it does not directly explain hypoalbuminemia or hypocalcemia.
• Barter Syndrome or Gitelman Syndrome: These are rare genetic disorders affecting kidney function, leading to hypokalemia and hypocalcemia. They are less likely given the normal urine protein/creatinine ratio and the presence of edema and hypoalbuminemia, which are not typical features of these syndromes.

Each of these diagnoses requires careful consideration of the clinical presentation, laboratory findings, and additional diagnostic testing to determine the underlying cause of the infant's condition.