Differential Diagnosis for a 7-Year-Old Patient with Renal Transplant and Worsening Radiculopathy and Confusion

Single Most Likely Diagnosis

• Vitamin B12 Deficiency: Given the patient's history of being on a low protein diet for more than six months, a deficiency in vitamin B12 is highly plausible. Vitamin B12 plays a crucial role in the synthesis of myelin, and its deficiency can lead to neurological symptoms such as radiculopathy and confusion.

Other Likely Diagnoses

• Protein Malnutrition: Prolonged low protein diet can lead to protein malnutrition, which may cause a range of symptoms including neurological manifestations due to the lack of essential amino acids necessary for neurotransmitter synthesis and maintenance of neural tissues.
• Electrolyte Imbalance: Patients with a history of renal transplant are at risk for electrolyte imbalances, which can cause neurological symptoms. The low protein diet might also contribute to an imbalance, especially if not properly managed.
• Medication Side Effects: The patient might be on immunosuppressive medications post-transplant, some of which can have neurological side effects, including confusion and neuropathy.

Do Not Miss Diagnoses

• Hyperammonemia: Although less common, hyperammonemia can occur in patients with renal issues and can cause severe neurological symptoms, including confusion. It's crucial to rule out this condition due to its potential for severe outcomes.
• CNS Infection: Given the patient's immunocompromised state due to the renal transplant, central nervous system (CNS) infections (e.g., meningitis, encephalitis) must be considered, as they can present with confusion and neurological deficits.
• Posterior Reversible Encephalopathy Syndrome (PRES): This condition is associated with hypertension, immunosuppressive drugs, and can cause neurological symptoms. It's particularly important in a renal transplant patient due to the potential for hypertension and use of certain medications.

Rare Diagnoses

• Subacute Combined Degeneration (SCD): A rare condition associated with vitamin B12 deficiency, characterized by demyelination of the dorsal columns and corticospinal tracts of the spinal cord, leading to symptoms that could include radiculopathy and confusion.
• Wernicke's Encephalopathy: Although more commonly associated with thiamine deficiency in alcoholics, it could theoretically occur in any malnourished state, including a prolonged low protein diet, and presents with confusion, ataxia, and ophthalmoplegia.