Makindo Medical Notes

Related Subjects: |Metabolic acidosis |Lactic acidosis |Acute Kidney Injury (AKI) / Acute Renal Failure

Fanconi Syndrome is a rare disorder of the proximal renal tubules where they fail to reabsorb essential solutes. This leads to the urinary loss of glucose, amino acids, phosphate, bicarbonate, and electrolytes, causing growth problems, bone disease, and metabolic acidosis.

About 🧾

• Fanconi Syndrome: A disorder of non-selective tubular dysfunction in the proximal nephron.
• Results in excessive urinary loss of key substances: glucose, amino acids, phosphate, bicarbonate, potassium, and uric acid.
• Can be inherited (genetic) or acquired (toxins, drugs, systemic disease).

Aetiology 🔬

• Failure of the proximal tubules (lined with microvilli) to reabsorb filtered solutes.
• Defects may be congenital (enzyme/transport abnormalities) or secondary to tubular injury.
• Key result → renal tubular acidosis type 2 + bone and growth abnormalities.

Causes ⚠️

• Inherited:
  • 🟡 Cystinosis (most common in children).
  • 🍼 Galactosaemia, hereditary fructose intolerance.
  • 🧬 Wilson’s disease, tyrosinaemia.
  • Lowe syndrome (oculocerebrorenal syndrome), mitochondrial DNA defects.
• Acquired:
  • ☣️ Heavy metal poisoning (lead, cadmium, arsenic).
  • 🧩 Plasma cell dyscrasias: multiple myeloma, amyloidosis, MGUS.
  • 🧪 Drugs: Tenofovir, ifosfamide, outdated tetracyclines.
  • Medullary cystic kidney disease.

Clinical Features 👩‍⚕️

• 📉 Failure to thrive: especially in children due to nutrient loss.
• 🚰 Polyuria & Polydipsia: excessive urination and thirst.
• ⚡ Hypokalaemia: muscle weakness, cramps, nocturia.
• 🌡️ Metabolic acidosis: nausea, anorexia, acidaemia.
• 🦴 Bone disease: Rickets in children, osteomalacia in adults (due to phosphate and vitamin D abnormalities).
• Oedema and growth delay may occur in severe cases.

Investigations 🔍

• Urine: Glucosuria (normal blood glucose), aminoaciduria, phosphaturia, uricosuria, bicarbonaturia, ↑ urinary K⁺.
• Bloods: Hypokalaemia, hypophosphataemia, low bicarbonate (metabolic acidosis), ± vitamin D deficiency.
• Other: Reduced conversion of 25(OH)D → 1,25(OH)₂D contributes to rickets/osteomalacia.

Management ⚕️

• 🎯 Treat underlying cause: (e.g., chelation for Wilson’s, stop nephrotoxic drugs).
• 💊 Replace losses: Oral phosphate, potassium, bicarbonate, magnesium, and vitamin D supplements.
• 🧃 High-calorie nutrition and careful growth monitoring in children.
• Long-term follow-up with nephrology ± metabolic/genetics teams.

Clinical Pearl 💡

Think of Fanconi syndrome in a child with failure to thrive + polyuria + rickets or in an adult with bone pain + metabolic acidosis + glucosuria with normal blood sugar.