Differential Diagnosis for a 12-year-old boy with abnormal lab results

The patient presents with low albumin (4.3 g/dL), elevated phosphorus (5.5 mg/dL), and slightly elevated creatinine (0.61 mg/dL). These findings can indicate various conditions affecting the kidneys, liver, or nutritional status. Here's a categorized differential diagnosis:

• Single most likely diagnosis

  • Nephrotic syndrome: This condition is characterized by heavy proteinuria, hypoalbuminemia, hyperlipidemia, and edema. The low albumin level in this patient is a key indicator, as significant protein loss in the urine can lead to hypoalbuminemia. Nephrotic syndrome can also lead to elevated phosphorus levels due to decreased excretion.

• Other Likely diagnoses

  • Chronic kidney disease (CKD): CKD can cause a range of biochemical abnormalities, including elevated creatinine and phosphorus levels. The slightly elevated creatinine suggests some degree of kidney dysfunction.
  • Liver disease: Certain liver conditions, such as cirrhosis, can lead to hypoalbuminemia due to decreased albumin synthesis. However, liver disease would typically present with other abnormalities in liver function tests.
  • Malnutrition: Poor dietary intake or malabsorption can result in low albumin levels. This could be a contributing factor, especially if the patient has a history of inadequate nutrition.

• Do Not Miss (ddxs that may not be likely, but would be deadly if missed)

  • Acute kidney injury (AKI): Although the creatinine is only slightly elevated, AKI is a critical condition that requires prompt diagnosis and treatment. It can be caused by various factors, including dehydration, medications, or obstructive uropathy.
  • Vasculitis (e.g., Henoch-Schönlein purpura): This condition can cause kidney inflammation, leading to abnormalities in kidney function tests, including elevated creatinine and phosphorus.

• Rare diagnoses

  • Fanconi syndrome: A rare genetic disorder characterized by impaired proximal tubular function in the kidneys, leading to excessive loss of glucose, amino acids, and phosphate in the urine. This could explain the elevated phosphorus level.
  • Lactic acidosis: A condition that can lead to elevated creatinine and phosphorus levels due to metabolic disturbances. It is often associated with mitochondrial disorders or certain medications.
  • Inborn errors of metabolism: Certain metabolic disorders can affect kidney function or lead to abnormal laboratory results, including elevated phosphorus levels. Examples include cystinosis or tyrosinemia.