Fanconi syndrome - Revision history

Danbot: Strip excess bold

2026-03-22T09:36:50Z

Strip excess bold

← Older revision		Revision as of 09:36, 22 March 2026
Line 47:		Line 47:
	===Acute/ED presentation===		===Acute/ED presentation===
	* [[Hypokalemia]] — may be '''severe and life-threatening'''; case reports of [[Cardiac arrest\|cardiac arrest]] from Fanconi-related hypokalemia<ref name="Cardiac">A 57-Year-Old Female Presenting With Cardiopulmonary Arrest Secondary to Severe Hypokalemia From a Fanconi-Like Syndrome. ''Cureus''. 2024;16(3):e55705. doi:10.7759/cureus.55705</ref>		* [[Hypokalemia]] — may be '''severe and life-threatening'''; case reports of [[Cardiac arrest\|cardiac arrest]] from Fanconi-related hypokalemia<ref name="Cardiac">A 57-Year-Old Female Presenting With Cardiopulmonary Arrest Secondary to Severe Hypokalemia From a Fanconi-Like Syndrome. ''Cureus''. 2024;16(3):e55705. doi:10.7759/cureus.55705</ref>
	* [[Metabolic acidosis]] — non-anion gap (hyperchloremic) from ~~'''~~proximal (type 2) [[Renal tubular acidosis\|RTA]]~~'''~~ (bicarbonate wasting)		* [[Metabolic acidosis]] — non-anion gap (hyperchloremic) from proximal (type 2) [[Renal tubular acidosis\|RTA]] (bicarbonate wasting)
	* Polyuria, polydipsia (from impaired water/sodium reabsorption)		* Polyuria, polydipsia (from impaired water/sodium reabsorption)
	* Dehydration, volume depletion		* Dehydration, volume depletion
Line 126:		Line 126:

	===Diagnosis===		===Diagnosis===
	*Clinical diagnosis based on the ~~'''~~constellation~~'''~~ of: glycosuria with normoglycemia + generalized aminoaciduria + phosphaturia + bicarbonaturia + hypokalemia<ref name="MerckManual">Fanconi Syndrome. ''Merck Manual Professional Edition''. 2024.</ref>		*Clinical diagnosis based on the constellation of: glycosuria with normoglycemia + generalized aminoaciduria + phosphaturia + bicarbonaturia + hypokalemia<ref name="MerckManual">Fanconi Syndrome. ''Merck Manual Professional Edition''. 2024.</ref>
	*No single test is diagnostic; the ~~'''~~pattern~~'''~~ of proximal tubular losses is key		*No single test is diagnostic; the pattern of proximal tubular losses is key
	*Once Fanconi syndrome is identified, the underlying cause must be sought		*Once Fanconi syndrome is identified, the underlying cause must be sought

Line 133:		Line 133:
	===Emergency management (acute presentations)===		===Emergency management (acute presentations)===
	* Hypokalemia:		* Hypokalemia:
	**Aggressive IV and PO potassium repletion; may be ~~'''~~profoundly refractory~~'''~~ due to ongoing renal losses<ref name="Cardiac"/>		**Aggressive IV and PO potassium repletion; may be profoundly refractory due to ongoing renal losses<ref name="Cardiac"/>
	**Continuous cardiac monitoring if K⁺ <3.0 mEq/L or symptomatic		**Continuous cardiac monitoring if K⁺ <3.0 mEq/L or symptomatic
	**Target serum K⁺ >4.0 mEq/L		**Target serum K⁺ >4.0 mEq/L
	**Consider ~~'''~~amiloride~~'''~~ or ~~'''~~spironolactone~~'''~~ to reduce renal potassium wasting		**Consider amiloride or spironolactone to reduce renal potassium wasting
	* Metabolic acidosis:		* Metabolic acidosis:
	**Oral or IV ~~'''~~sodium bicarbonate~~'''~~ or ~~'''~~sodium citrate/potassium citrate~~'''~~ (Bicitra, Polycitra)		**Oral or IV sodium bicarbonate or sodium citrate/potassium citrate (Bicitra, Polycitra)
	**Large doses may be required (10-15 mEq/kg/day in children) because bicarbonate is lost in the urine		**Large doses may be required (10-15 mEq/kg/day in children) because bicarbonate is lost in the urine
	**Caution: bicarbonate repletion may worsen hypokalemia (drives K⁺ intracellularly and increases distal delivery); replete potassium FIRST or concurrently		**Caution: bicarbonate repletion may worsen hypokalemia (drives K⁺ intracellularly and increases distal delivery); replete potassium FIRST or concurrently
Line 152:		Line 152:
	**Valproic acid: consider alternative antiepileptic		**Valproic acid: consider alternative antiepileptic
	**Expired tetracyclines: discard		**Expired tetracyclines: discard
	**Recovery after drug withdrawal may take ~~'''~~weeks to months~~'''~~<ref name="Medscape"/>		**Recovery after drug withdrawal may take weeks to months<ref name="Medscape"/>
	* Heavy metal poisoning: chelation therapy as appropriate (see [[Lead poisoning]])		* Heavy metal poisoning: chelation therapy as appropriate (see [[Lead poisoning]])
	* Multiple myeloma/paraproteinemia: hematology/oncology referral for treatment of underlying disease		* Multiple myeloma/paraproteinemia: hematology/oncology referral for treatment of underlying disease
	* Cystinosis: ~~'''~~cysteamine~~'''~~ (Cystagon) — reduces intracellular cystine accumulation; early initiation improves renal outcomes		* Cystinosis: cysteamine (Cystagon) — reduces intracellular cystine accumulation; early initiation improves renal outcomes

	===Long-term supplementation===		===Long-term supplementation===

Danbot: Moved intro paragraph into Background as bullets; removed excessive bold from bullet lead-ins; added Renal tubular disorders, Hypokalemia, and Acid-base disorders DDX templates; bold retained for critical items only

2026-03-19T14:27:32Z

Moved intro paragraph into Background as bullets; removed excessive bold from bullet lead-ins; added Renal tubular disorders, Hypokalemia, and Acid-base disorders DDX templates; bold retained for critical items only

Show changes

Ostermayer: Created page with "Fanconi syndrome is a generalized dysfunction of the '''proximal renal tubule''' resulting in impaired reabsorption of glucose, amino acids, phosphate, bicarbonate, uric acid, potassium, sodium, and low-molecular-weight proteins. It produces a '''type 2 (proximal) renal tubular acidosis''' and may cause life-threatening hypokalemia, metabolic acidosis, dehydration, and bone disease.F..."

2026-03-17T23:43:39Z

Created page with "Fanconi syndrome is a generalized dysfunction of the '''proximal renal tubule''' resulting in impaired reabsorption of glucose, amino acids, phosphate, bicarbonate, uric acid, potassium, sodium, and low-molecular-weight proteins. It produces a '''type 2 (proximal) renal tubular acidosis''' and may cause life-threatening hypokalemia, metabolic acidosis, dehydration, and bone disease.<ref name="StatPearls">F..."

New page

Fanconi syndrome is a generalized dysfunction of the '''proximal renal tubule''' resulting in impaired reabsorption of glucose, amino acids, phosphate, bicarbonate, uric acid, potassium, sodium, and low-molecular-weight proteins. It produces a '''type 2 (proximal) [[Renal tubular acidosis|renal tubular acidosis]]''' and may cause life-threatening [[Hypokalemia|hypokalemia]], [[Metabolic acidosis|metabolic acidosis]], dehydration, and bone disease.<ref name="StatPearls">Fanconi Syndrome. ''StatPearls''. 2025. PMID: 30521243</ref> It is '''not''' the same as [[Fanconi anemia]], which is a separate inherited bone marrow failure syndrome.

==Background==
*The proximal convoluted tubule (PCT) normally reabsorbs ~65% of filtered sodium, water, bicarbonate, glucose, amino acids, phosphate, and uric acid
*In Fanconi syndrome, '''global PCT dysfunction''' causes urinary wasting of all these solutes simultaneously<ref name="StatPearls"/>
*Pathophysiology centers on '''mitochondrial dysfunction → ATP depletion → failure of Na⁺/K⁺-ATPase''' and energy-dependent transport systems<ref name="StatPearls"/>
*Can be '''inherited''' or '''acquired'''; acquired forms are more relevant to the emergency physician

===Inherited causes===
*'''[[Cystinosis]]''' — most common inherited cause (presents in infancy, 6-18 months)
*[[Wilson disease]]
*Hereditary fructose intolerance
*Galactosemia
*Glycogen storage diseases
*Lowe syndrome (oculocerebrorenal syndrome)
*Dent disease
*Fanconi-Bickel syndrome
*Tyrosinemia type 1
*Mitochondrial cytopathies

===Acquired causes (most EM-relevant)===
*'''Medications''' (most common acquired cause):<ref name="StatPearls"/><ref name="Medscape">Fanconi Syndrome. ''Medscape''. 2024.</ref>
**'''Tenofovir''' (TDF; especially in HIV patients with pre-existing renal impairment) — most commonly encountered drug cause today
**'''Ifosfamide''' — particularly in children after cumulative doses
**'''Cisplatin, carboplatin'''
**'''Valproic acid''' — especially with polytherapy and prolonged use
**'''Expired tetracyclines''' (degradation products are directly nephrotoxic)
**Adefovir, cidofovir, didanosine
**Aminoglycosides (gentamicin)
**Lenalidomide, streptozocin
*'''Heavy metals:'''
**[[Lead poisoning]] (most common heavy metal cause in children)
**Cadmium, mercury, platinum, uranium
*'''Paraproteinemia:'''
**[[Multiple myeloma]] (light chain proximal tubulopathy)
**AL amyloidosis
*'''Other:'''
**Renal transplant
**Toluene exposure (glue sniffing)
**Aristolochic acid (herbal medicines)
**Paraquat poisoning

==Clinical features==
*Presentation varies widely depending on the underlying cause, severity, and chronicity
*May range from an incidental laboratory finding to life-threatening electrolyte emergency

===Acute/ED presentation===
*'''[[Hypokalemia]]''' — may be '''severe and life-threatening'''; case reports of [[Cardiac arrest|cardiac arrest]] from Fanconi-related hypokalemia<ref name="Cardiac">A 57-Year-Old Female Presenting With Cardiopulmonary Arrest Secondary to Severe Hypokalemia From a Fanconi-Like Syndrome. ''Cureus''. 2024;16(3):e55705. doi:10.7759/cureus.55705</ref>
*'''[[Metabolic acidosis]]''' — non-anion gap (hyperchloremic) from '''proximal (type 2) [[Renal tubular acidosis|RTA]]''' (bicarbonate wasting)
*'''Polyuria, polydipsia''' (from impaired water/sodium reabsorption)
*'''Dehydration''', volume depletion
*'''Muscle weakness''' (from hypokalemia and hypophosphatemia)
*Nausea, vomiting
*Fatigue, malaise

===Chronic/subacute presentation===
*'''Children:'''
**Failure to thrive, growth retardation
**'''Rickets''' (hypophosphatemic; from phosphate wasting + impaired 1,25-dihydroxyvitamin D synthesis in PCT)
**Bone pain, pathologic fractures
**Polyuria, polydipsia
*'''Adults:'''
**'''Osteomalacia''' (bone pain, pathologic fractures, proximal muscle weakness)
**Chronic fatigue, muscle weakness
**Kidney stones (hypercalciuria in some forms)
**Progressive chronic kidney disease
*'''Cystinosis-specific:''' corneal cystine crystals, hepatomegaly, hypothyroidism, retinal depigmentation, growth failure

===Key laboratory pattern ("the Fanconi fingerprint")===
*'''Glycosuria with NORMAL serum glucose''' (not diabetes — inappropriately low renal glucose threshold)
*'''Generalized aminoaciduria'''
*'''Phosphaturia''' with hypophosphatemia
*'''Bicarbonaturia''' with non-anion gap metabolic acidosis (proximal RTA)
*'''Hypokalemia''' (renal potassium wasting)
*'''Hypouricemia''' (uric acid wasting)
*'''Low-molecular-weight proteinuria''' (β₂-microglobulin, retinol-binding protein)

==Differential diagnosis==
===Proximal [[Renal tubular acidosis]]===
*Isolated proximal RTA (type 2) without full Fanconi features
*[[Renal tubular acidosis]] (type 1)
*Type 4 RTA (hypoaldosteronism)

===Other causes of non-anion gap metabolic acidosis===
*Diarrhea
*Ureteral diversion
*Carbonic anhydrase inhibitors (acetazolamide)

===Other causes of unexplained hypokalemia===
*Diuretic use
*[[Hyperaldosteronism]]
*[[Bartter syndrome]], [[Gitelman syndrome]]
*Vomiting, GI losses
*Licorice ingestion

===Other causes of glycosuria with normal glucose===
*Renal glycosuria (isolated SGLT2 mutation)
*Pregnancy

==Evaluation==
===Workup===
*'''BMP:''' hypokalemia, hypophosphatemia, low bicarbonate (non-anion gap metabolic acidosis), low uric acid; BUN/creatinine for renal function
*'''ABG/VBG:''' non-anion gap metabolic acidosis (hyperchloremic); urine pH may be <5.5 (unlike distal RTA) if serum bicarbonate is below the reabsorptive threshold
*'''Urinalysis:'''
**'''Glucosuria''' (with normal serum glucose — the hallmark clue)
**Proteinuria (low-molecular-weight)
*'''Urine electrolytes:''' elevated urine potassium (transtubular potassium gradient >7 suggests renal K⁺ wasting)
*'''Urine amino acids:''' generalized aminoaciduria (elevated excretion of virtually all amino acids)
*'''Fractional excretion of phosphate (FePO₄):''' elevated (>5%)
*'''Fractional excretion of uric acid:''' elevated (>10%)
*'''Serum phosphate, uric acid, calcium, magnesium, vitamin D (25-OH and 1,25-OH), PTH'''
*'''Urine β₂-microglobulin''' — marker of proximal tubular injury<ref name="StatPearls"/>
*'''ECG:''' assess for hypokalemia-related changes (U waves, flattened T waves, ST depression, prolonged QT, arrhythmias)
*'''Additional workup directed at underlying cause:'''
**Medication review (tenofovir, valproic acid, ifosfamide, expired tetracyclines)
**Serum and urine protein electrophoresis, free light chains (multiple myeloma)
**Serum copper, ceruloplasmin ([[Wilson disease]])
**Lead level
**White blood cell cystine level (cystinosis)
**Slit-lamp examination (cystine corneal crystals)

===Diagnosis===
*Clinical diagnosis based on the '''constellation''' of: glycosuria with normoglycemia + generalized aminoaciduria + phosphaturia + bicarbonaturia + hypokalemia<ref name="MerckManual">Fanconi Syndrome. ''Merck Manual Professional Edition''. 2024.</ref>
*No single test is diagnostic; the '''pattern''' of proximal tubular losses is key
*Once Fanconi syndrome is identified, the underlying cause must be sought

==Management==
===Emergency management (acute presentations)===
*'''Hypokalemia:'''
**Aggressive IV and PO potassium repletion; may be '''profoundly refractory''' due to ongoing renal losses<ref name="Cardiac"/>
**Continuous cardiac monitoring if K⁺ <3.0 mEq/L or symptomatic
**Target serum K⁺ >4.0 mEq/L
**Consider '''amiloride''' or '''spironolactone''' to reduce renal potassium wasting
*'''Metabolic acidosis:'''
**Oral or IV '''sodium bicarbonate''' or '''sodium citrate/potassium citrate''' (Bicitra, Polycitra)
**Large doses may be required (10-15 mEq/kg/day in children) because bicarbonate is lost in the urine
**Caution: bicarbonate repletion may worsen hypokalemia (drives K⁺ intracellularly and increases distal delivery); replete potassium FIRST or concurrently
*'''Dehydration:''' IV fluid resuscitation; may need large volumes due to polyuria
*'''Hypophosphatemia:'''
**Oral phosphate supplementation (Neutra-Phos, K-Phos)
**IV phosphate if severe (<1 mg/dL) or symptomatic
*'''Hypoglycemia:''' IV dextrose if present (hereditary fructose intolerance may present with hypoglycemia)

===Identify and treat the underlying cause===
*'''Drug-induced:''' '''discontinue the offending agent''' — this is the most important intervention for acquired Fanconi syndrome<ref name="StatPearls"/>
**Tenofovir: switch to tenofovir alafenamide (TAF) or alternative antiretroviral
**Valproic acid: consider alternative antiepileptic
**Expired tetracyclines: discard
**Recovery after drug withdrawal may take '''weeks to months'''<ref name="Medscape"/>
*'''Heavy metal poisoning:''' chelation therapy as appropriate (see [[Lead poisoning]])
*'''Multiple myeloma/paraproteinemia:''' hematology/oncology referral for treatment of underlying disease
*'''Cystinosis:''' '''cysteamine''' (Cystagon) — reduces intracellular cystine accumulation; early initiation improves renal outcomes

===Long-term supplementation===
*'''Bicarbonate/citrate:''' oral sodium bicarbonate or potassium citrate for chronic metabolic acidosis
*'''Phosphate:''' oral phosphate supplements
*'''Vitamin D:''' calcitriol (1,25-dihydroxyvitamin D) — PCT dysfunction impairs conversion of 25-OH to active form
*'''Potassium:''' oral supplementation; potassium-sparing diuretics if refractory
*Nephrology follow-up for ongoing management and monitoring of renal function

==Disposition==
*'''Severe hypokalemia (K⁺ <2.5 mEq/L), symptomatic hypokalemia, or cardiac arrhythmias:''' admit to monitored setting; continuous telemetry; serial electrolytes<ref name="Cardiac"/>
*'''Severe metabolic acidosis (pH <7.2):''' admit for IV bicarbonate and electrolyte management
*'''Significant dehydration or hemodynamic instability:''' admit for IV resuscitation
*'''New diagnosis of Fanconi syndrome:''' may require admission or urgent outpatient workup depending on severity; nephrology consultation
*'''Stable, known Fanconi syndrome with mild electrolyte abnormalities:''' outpatient management with close nephrology follow-up, medication adjustment, and return precautions for weakness, palpitations, or syncope
*'''Medication-induced Fanconi:''' ensure offending drug is held and arrange nephrology and primary care follow-up for drug substitution and monitoring of recovery

==See Also==
*[[Renal tubular acidosis]]
*[[Hypokalemia]]
*[[Hypophosphatemia]]
*[[Metabolic acidosis]]
*[[Multiple myeloma]]
*[[Wilson disease]]
*[[Lead poisoning]]
*[[Tenofovir]]
*[[Cystinosis]]

==External Links==
*[https://www.ncbi.nlm.nih.gov/books/NBK534872/ StatPearls — Fanconi Syndrome]
*[https://emedicine.medscape.com/article/981774-overview Medscape — Fanconi Syndrome]
*[https://www.merckmanuals.com/professional/genitourinary-disorders/renal-transport-abnormalities/fanconi-syndrome Merck Manual — Fanconi Syndrome]
*[https://pmc.ncbi.nlm.nih.gov/articles/PMC10960066/ Cureus — Cardiopulmonary Arrest Secondary to Severe Hypokalemia From Fanconi-Like Syndrome (2024)]

==References==
<references/>

[[Category:Renal]]