Condition Deep-Dives 11 min read·Updated 22 July 2026 Clinician-reviewed

Renal Fanconi Syndrome

A UK Consultant Nephrologist on renal Fanconi syndrome — the generalised proximal tubular dysfunction that causes glycosuria with normal blood glucose, hypophosphataemic bone disease, proximal RTA and progressive CKD. Most adult cases are drug-induced or paraprotein-related; most paediatric cases are inherited.

  • Clinically Reviewed
  • NHS & NICE Aligned
  • UK Evidence-Based
  • Last Reviewed 22 July 2026

Professor Mohammed Mahdi Althaf

Consultant Nephrologist & Acute Physician

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Professor Mohammed Mahdi Althaf

MD, MSc, PgDip (Clin Ed), FRCP, FHEA, FASN

Consultant Nephrologist & Acute Physician · GMC 7216325

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Direct answer

Fanconi syndrome = generalised proximal tubular wasting (glucose, amino acids, phosphate, bicarbonate, urate, LMW proteins). Adults: tenofovir, ifosfamide, myeloma. Children: cystinosis, Dent, Lowe, mitochondrial disease. Treat by removing the cause and aggressive replacement (bicarbonate, phosphate, potassium, vitamin D).

Key recommendation: Glycosuria with normal blood glucose = key clue.

Quick answer

✓ Best choices

  • Vegetables, lower-potassium fruit and whole grains
  • Sensible portions of fish, eggs, chicken or tofu
  • Olive oil and unsalted nuts in small amounts

✓ Foods to limit

  • Added salt and ultra-processed foods
  • Phosphate additives in processed meats and ready meals
  • Sugary and energy drinks

Key takeaway

Fanconi syndrome = generalised proximal tubular wasting (glucose, amino acids, phosphate, bicarbonate, urate, LMW proteins). Adults: tenofovir, ifosfamide, myeloma. Children: cystinosis, Dent, Lowe, mitochondrial disease. Treat by removing the cause and aggressive replacement (bicarbonate, phosphate, potassium, vitamin D).

Who should be cautious

People on dialysis, post-transplant, pregnant or breastfeeding, or taking prescription medication — confirm with your renal team before changes.

Renal Fanconi Syndrome

Biochemistry & diagnosis

DIAGNOSTIC CRITERIA — any combination of:

  • Glycosuria with normal plasma glucose
  • Generalised aminoaciduria (24-h urine amino acid screen)
  • Hypophosphataemia from urinary phosphate wasting (low tubular reabsorption of phosphate — TmP/GFR < 0.8)
  • Proximal renal tubular acidosis (type 2 RTA): low serum bicarbonate, urine HCO₃⁻ wasting at therapeutic doses
  • Hypouricaemia from urinary urate wasting (FE-urate > 10%)
  • Low-molecular-weight proteinuria (beta-2-microglobulin, alpha-1-microglobulin, retinol-binding protein high in urine)
  • Tubular dysfunction-pattern proteinuria (often modest by 24h total)

Clinical Manifestations

  • Bone disease — rickets in children, osteomalacia in adults; bone pain, weakness, pseudofractures
  • Failure to thrive, short stature in children
  • Polyuria, polydipsia
  • Hypokalaemic muscle weakness
  • Volume depletion
  • Slowly progressive CKD

Investigations

  • Bloods: U&E, bicarbonate, phosphate, calcium, alkaline phosphatase, urate, magnesium, glucose, PTH, 25-OH vitamin D, immunoglobulins, serum free light chains, SPEP
  • Urine: ACR, 24-h urine for amino acids, phosphate (TmP/GFR), urate, glucose, LMW protein screen
  • Imaging: X-rays for rickets/osteomalacia; renal USS
  • Bone densitometry
  • Drug history (TDF, ifosfamide, valproate, deferasirox, aminoglycoside, tetracycline)
  • Heavy metal screen if exposure suspected
  • Genetic testing where inherited disease likely (NHS panels: R190 inherited tubulopathies)

Causes by group

Adult Causes

1. DRUGS (commonest):

  • Tenofovir disoproxil fumarate (TDF) — switch to tenofovir alafenamide (TAF)
  • Ifosfamide — dose-related; mitigated by co-administered Mesna
  • Cisplatin
  • Valproate
  • Adefovir, cidofovir
  • Aminoglycosides
  • Expired tetracycline
  • Deferasirox
  • High-dose corticosteroids (rare)

2. Paraprotein / Myeloma

  • Light-chain proximal tubulopathy (kappa > lambda)
  • Often with crystalline inclusions in proximal tubular cells
  • Myeloma must be considered in every adult with new Fanconi syndrome

3. Autoimmune

  • Sjögren syndrome
  • Tubulointerstitial nephritis with uveitis (TINU)

4. Heavy Metals

  • Lead, cadmium, mercury, uranium
  1. WILSON'S DISEASE (under-diagnosed; check caeruloplasmin, 24-h urinary copper)

Paediatric Causes

  1. CYSTINOSIS (CTNS) — autosomal recessive; cysteine crystals accumulate intracellularly. Infantile form presents at 6–18 months with failure to thrive, rickets, polyuria. CYSTEAMINE (Procysbi / Cystagon) delayed-release reduces cystine load. Lifelong specialist care.
  1. DENT DISEASE (CLCN5, X-linked) — LMW proteinuria, hypercalciuria, stones, slow CKD
  1. LOWE SYNDROME (OCRL, X-linked) — congenital cataracts, intellectual disability, Fanconi
  1. TYROSINAEMIA TYPE I — treat with nitisinone + low-tyrosine/phenylalanine diet
  1. GALACTOSAEMIA, HEREDITARY FRUCTOSE INTOLERANCE — dietary management
  1. MITOCHONDRIAL CYTOPATHY (MELAS, Kearns-Sayre, etc.)
  1. WILSON'S DISEASE
  1. GLYCOGEN STORAGE DISEASE Ia

All suspected inherited cases should be referred to a regional paediatric inherited metabolic disease/nephrology centre.

Management

1. Remove / Treat The Cause

  • Switch TDF to TAF
  • Stop / reduce ifosfamide, valproate, deferasirox where possible
  • Treat multiple myeloma (bortezomib-dexamethasone-based induction)
  • Start cysteamine for cystinosis
  • Chelation for heavy metals
  • Specific dietary therapies for inherited metabolic disease

2. Replace What Is Lost

  • POTASSIUM-CITRATE/BICARBONATE: typically 1–3 mmol/kg/day in adults (much higher in children) to maintain bicarbonate > 22 mmol/L
  • NEUTRAL PHOSPHATE supplement (Phosphate-Sandoz): 30–80 mmol/day in divided doses; titrate to phosphate 0.8–1.1 mmol/L (over-replacement causes diarrhoea and stones)
  • ALFACALCIDOL (1-alpha-calcidol) 0.25–1 microgram/day for bone disease
  • POTASSIUM CHLORIDE if hypokalaemia not corrected by potassium citrate
  • MAGNESIUM if hypomagnesaemia
  • Adequate fluids

3. Bone Protection

  • DEXA scan; vitamin D adequacy
  • Avoid bisphosphonates if hypocalcaemia / vitamin D deficient
  • Paediatric — coordinate with endocrinology for growth, growth hormone if indicated

4. Avoid Further Nephrotoxins

  • NSAIDs
  • IV contrast where possible
  • Concomitant ACE/ARB risk in volume-depleted patients

5. CKD Management

  • Standard BP control (ACEI/ARB if tolerated and proteinuria significant)
  • Lipids, glycaemia, smoking
  • Renal anaemia, secondary hyperparathyroidism management at later stages

6. Follow-up

  • Adult drug-related Fanconi: often improves substantially over 6–12 months after stopping drug; some residual tubular dysfunction may persist
  • Myeloma-related: parallels haematological response
  • Cystinosis: lifelong specialist care; cysteamine has transformed outcomes
  • Other inherited: lifelong renal + metabolic team

7. Transplantation

  • Outcomes good for most causes
  • Cystinosis does not recur in the graft (the intracellular cystine accumulation is body-wide, but the new kidney's tubules are normal)
  • Lowe / Dent: as above
  • Myeloma: depends on haematological remission
Renal Tubular Acidosis (RTA)
Related reading: Renal Tubular Acidosis (RTA).

Key practical tips

Designed for quick scanning — what to order, what to avoid, sensible portions, common mistakes.

  • Cook from scratch when you can
  • Read sodium labels (≤ 0.3 g per 100 g is low)
  • Take any concerns to your GP or renal team early

Clinical guidance

TL;DR summary

Fanconi syndrome = generalised proximal tubular wasting (glucose, amino acids, phosphate, bicarbonate, urate, LMW proteins). Adults: tenofovir, ifosfamide, myeloma. Children: cystinosis, Dent, Lowe, mitochondrial disease. Treat by removing the cause and aggressive replacement (bicarbonate, phosphate, potassium, vitamin D).

Key takeaways
  • Glycosuria with normal blood glucose = key clue.
  • Adults: tenofovir, ifosfamide, multiple myeloma.
  • Children: cystinosis, Dent, Lowe — refer to specialist centre.
  • Treat cause + replace bicarbonate, phosphate, potassium, vitamin D.
  • Long-term joint nephrology + endocrine + bone care.
Kidney Diet & Nutrition Considerations

Diet is one of the most powerful tools you have to look after your kidneys. UK renal guidance points to a Mediterranean-style, reduced-salt pattern: plenty of vegetables, lower-potassium fruit, whole grains, sensible protein, beans and pulses in moderation, oily fish and olive oil. Personal targets — for potassium, phosphate, protein and fluid — should be set by your renal team based on your bloods.

Foods to prioritise

  • Vegetables, lower-potassium fruit and whole grains
  • Sensible portions of fish, eggs, chicken or tofu
  • Olive oil and unsalted nuts in small amounts

Foods to limit

  • Added salt and ultra-processed foods
  • Phosphate additives in processed meats and ready meals
  • Sugary and energy drinks

Potassium, phosphate and protein needs vary between individuals — please confirm personal targets with your renal team or dietitian. Browse the Kidney Diet Hub for more guides in this cluster.

Frequently asked questions

What is Fanconi syndrome?

Renal Fanconi syndrome is generalised proximal tubular dysfunction. The proximal tubule normally reabsorbs glucose, amino acids, phosphate, bicarbonate, urate and low-molecular-weight proteins; in Fanconi syndrome all of these are inappropriately wasted in the urine. The result is glycosuria with normal blood glucose, generalised aminoaciduria, hypophosphataemia, proximal (type 2) renal tubular acidosis, hypouricaemia and tubular proteinuria.

What causes it in adults?

Drugs are the commonest cause — tenofovir disoproxil (TDF), ifosfamide, cisplatin, valproate, aminoglycosides, expired tetracycline, deferasirox and adefovir. Multiple myeloma with light-chain proximal tubulopathy is an important second group. Heavy metals (lead, cadmium, mercury), Wilson's disease and paraproteinaemias account for many remaining cases.

What about children?

Inherited causes dominate: nephropathic CYSTINOSIS (CTNS gene) is the commonest in children — presents in infancy with failure to thrive and rickets. Other inherited forms: Dent disease (CLCN5), Lowe syndrome (OCRL), tyrosinaemia, galactosaemia, hereditary fructose intolerance, mitochondrial disease, Wilson's disease, and inherited glycogen storage disease. Cysteamine (Procysbi) is the disease-modifying treatment for cystinosis and is delivered through NHS specialist paediatric metabolic centres.

How is it treated?

Find and remove the cause (stop the drug, treat the myeloma, start cysteamine for cystinosis). Replace what is being lost: oral bicarbonate / potassium citrate for acidosis, neutral phosphate supplementation, vitamin D (1-alpha-calcidol or alfacalcidol) for the bone disease, potassium chloride for hypokalaemia, and adequate fluids. Sodium-glucose handling means SGLT2 inhibitors are usually unnecessary and avoided.

What foods are good for kidney health?

A Mediterranean-style, mostly plant-based, reduced-salt diet is the most consistent evidence-based pattern for kidney health. Build meals around vegetables, lower-potassium fruit, whole grains, fish, eggs or tofu, beans and pulses in moderation, and olive oil.

Nutritional challenges in kidney disease

Many people living with kidney disease have to limit foods because of potassium, phosphate, diabetes, dialysis, appetite changes or simply the time it takes to cook from scratch every day. That can make it harder to keep daily nutrition balanced — particularly for vitamins and minerals that food alone may not fully cover.

Kidney Vitality is a UK-formulated daily nutritional support product designed by Consultant Nephrologist Professor Mohammed Mahdi Althaf with renal nutrition in mind from the start. It keeps doses moderate, leaves out added potassium, phosphate and magnesium, and avoids megadose vitamin A — sitting alongside a kidney-friendly diet, not replacing it.

Why Kidney Vitality fits this need

Built around UK guidance

Aligned with UK Kidney Association tubular disease guidance, NICE TA734 (TDF/TAF in HIV), BSH myeloma guidance and NHS Genomic Test Directory R190 inherited tubulopathies panel.

Designed by a UK Consultant Nephrologist

Formulated and reviewed by Professor Mohammed Mahdi Althaf (GMC 7216325).

Joint metabolic, haematology and nephrology care

Practical UK guidance for finding the cause (drug, paraprotein, inherited) and replacing what is lost — bicarbonate, phosphate, potassium, vitamin D.

Designed by a UK Consultant Nephrologist

Ready to support your kidney health?

If you have been researching kidney health, supplements, CKD nutrition or kidney-friendly living, Kidney Vitality was developed specifically around those principles by Professor Mohammed Mahdi Althaf (GMC 7216325). Nephrologist Developed Daily Multivitamin.

  • No Added Potassium
  • No Added Magnesium
  • No Added Phosphorus
  • No Added Iron
  • One capsule daily
  • UK GMP — BRCGS, NSF GMP, Halal
Subscribe & Save — £20.39/monthCheck your current multivitamin

✓ Free UK tracked delivery  ·  ✓ Delivered every 30 days  ·  ✓ Pause or cancel anytime  ·  ✓ Never run out

ComparisonKidney VitalityTypical high-street multivitamin
Added potassiumNoneOften included
Added phosphateNoneOften included (E338–E452)
Vitamin A (retinol)No megadoseOften high-dose retinol
Kidney-focused formulationYesNo — general population
Consultant Nephrologist involvementYes (GMC 7216325)No
UK GMP manufacturedYes (BRCGS, NSF GMP)Varies

Food supplement. Not a medicine and not a treatment for kidney disease. Speak with your GP, pharmacist or renal team before starting any new supplement, especially in advanced CKD, on dialysis, post-transplant, pregnant or breastfeeding.

Clinical reviewer

Professor Mohammed Mahdi Althaf

Consultant Nephrologist

Acute Physician

GMC 7216325

View Full Biography

Professor Mohammed Mahdi Althaf is a UK Consultant Nephrologist and Acute Physician with a special interest in chronic kidney disease, AKI prevention and renal nutrition. He combines hospital practice with patient education and clinical guidance review.

View professional profile →
View Credentials
  • MD
  • MSc
  • PgDip (Clin Ed)
  • FRCP
  • FHEA
  • FASN

About this article

Written for UK patients and based on:

  • NICE guidance
  • NHS resources
  • British Dietetic Association guidance
  • Kidney Care UK resources
View methodology

Each article is researched against current UK clinical guidance (NICE NG203, NG118, NG136), NHS patient resources, KDIGO and KDOQI international guidelines, and the British Dietetic Association Renal Nutrition Group. Drafts are written by the Kidney Vitality editorial team and reviewed by a UK Consultant Nephrologist before publication. Content is reviewed on a rolling basis and updated when guidance changes.

Editorial standards

  • Clinically reviewed
  • NHS-aligned
  • NICE-aligned
  • Evidence-based
  • Reviewed before publication
View full editorial process

Every article is researched and written by the Kidney Vitality editorial team using current UK clinical guidance (NICE NG203, NG118, NG136), NHS patient resources, KDIGO/KDOQI international guidelines, and British Dietetic Association renal nutrition guidance. Drafts are reviewed for clinical accuracy by Professor Mohammed Mahdi Althaf, MD, MSc, PgDip (Clin Ed), FRCP, FHEA, FASN (Consultant Nephrologist & Acute Physician, GMC 7216325) before publication. Content is updated when UK guidance changes.

References (4)View Sources
  1. NICE NG203: Chronic kidney disease — assessment and management
  2. KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of CKD
  3. KDOQI Clinical Practice Guideline for Nutrition in CKD: 2020 Update
  4. British Dietetic Association — Renal Nutrition Group

Medical disclaimer

This content is educational only and does not replace personalised medical advice.

Read full disclaimer

This page is general information, not personal medical advice. If you have chronic kidney disease, are on dialysis, have had a kidney transplant, are pregnant or breastfeeding, or take prescription medication, please confirm any supplement with your GP, pharmacist or renal team before starting.

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