Synopsis
Recognise generalised proximal tubular solute wasting, identify acquired and inherited causes, and replace phosphate, alkali and potassium through safe specialist monitoring.
- Fanconi syndrome is a generalised proximal-tubule reabsorptive defect, not Fanconi anaemia, and produces urinary loss of several filtered solutes rather than one isolated abnormality.
- Core clues include phosphate wasting, normoglycaemic glycosuria, aminoaciduria, bicarbonate loss causing proximal RTA, urate loss, potassium loss and low-molecular-weight proteinuria.
- A normal creatinine does not exclude substantial proximal dysfunction because tubular transport can fail before glomerular filtration falls.
Key red flags
Bone pain, waddling gait, proximal weakness and insufficiency fractures with low phosphate may represent renal-wasting osteomalacia rather than osteoporosis alone.
Investigation priorities
Demonstrate inappropriate renal loss of phosphate, glucose, urate, bicarbonate and potassium.
Management branches
Hypophosphataemia, glycosuria or tubular proteinuria suggests proximal dysfunction.
- Repeat serum phosphate, bicarbonate, potassium, glucose, urate, magnesium and creatinine while collecting appropriately timed urine chemistry.
- Demonstrate at least a coherent pattern of inappropriate urinary losses rather than diagnosing Fanconi syndrome from isolated glycosuria.
Key medicines
Oral phosphate saltsStart only with renal or metabolic specialist advice, using divided local-formulary doses titrated to symptoms, serum phosphate and urinary calcium rather than normalising one result rapidly.
Alfacalcidol or calcitriolUse only for a defined specialist indication with an agreed low starting dose and frequent calcium, phosphate and urine-calcium surveillance.