Fabry Disease — Causes, Symptoms, Diagnosis & Enzyme Replacement Therapy Guide — Symptoms, Causes & Treatment | MyMedicPlus

Fabry disease (Anderson-Fabry disease) is a rare, progressive, X-linked lysosomal storage disorder caused by deficiency or dysfunction of the enzyme alpha-galactosidase A (alpha-Gal A), encoded by the GLA gene on the X chromosome. Enzyme deficiency leads to progressive accumulation of glycosphingolipids — primarily globotriaosylceramide (Gb3, also known as GL-3) and its deacylated form lyso-Gb3 — in lysosomes throughout the body, particularly in endothelial cells, vascular smooth muscle, kidney (podocytes, tubular cells), cardiac myocytes, and neurons. This results in progressive multi-organ damage including hypertrophic cardiomyopathy, chronic kidney disease progressing to renal failure, cerebrovascular disease, and peripheral neuropathy. Classic Fabry disease affects hemizygous males severely; heterozygous females have variable expression due to lyonisation (X-inactivation) and can have significant disease despite historically being called 'carriers'. The estimated prevalence of classic Fabry disease is 1 in 40,000-117,000, though newborn screening data suggests the overall prevalence of GLA variants (including late-onset forms) may be considerably higher.

Fabry disease is caused by pathogenic variants in the GLA gene (Xq22.1) — over 900 distinct pathogenic variants have been identified. Inheritance is X-linked: hemizygous males (one X chromosome with the variant) typically have the most severe phenotype; heterozygous females have one affected and one unaffected X chromosome and show a variable spectrum from asymptomatic to severely affected. Classic Fabry disease: caused by variants that result in absent or severely reduced alpha-Gal A activity; presents in childhood with neuropathic pain, anhidrosis, angiokeratomas, and corneal whorling (cornea verticillata), progressing to life-threatening organ involvement. Late-onset variants: partial residual enzyme activity — typically present in adulthood with isolated cardiomyopathy or renal disease without the classic early-onset features. Lyso-Gb3 (plasma deacylated substrate): elevated in virtually all hemizygous males and many heterozygous females with significant disease — a useful biomarker for diagnosis, disease activity, and treatment monitoring. New mutations occur in approximately 10-15% of cases (de novo).

Classic Fabry disease (childhood onset in hemizygous males): neuropathic pain — episodic severe burning pain in the hands and feet (Fabry crises), often triggered by fever, exercise, or temperature change; in 60-80% of affected males in childhood. Autonomic dysfunction: anhidrosis (inability to sweat) or hypohidrosis leading to heat intolerance, exercise intolerance, and hyperthermia risk. Angiokeratomas: small dark-red to blue skin lesions, often clustered in the bathing trunk distribution (umbilicus, scrotum, buttocks, groin). Cornea verticillata (whorl-like corneal opacity visible on slit-lamp examination): present in virtually all affected males and >70% of heterozygous females — does not impair vision. Cardiac involvement: left ventricular hypertrophy (LVH — most common cardiac manifestation), arrhythmias (AF, heart block, pre-excitation), coronary artery disease, and mitral valve disease. Renal: progressive proteinuria and declining eGFR — leading to ESKD (median age 42 years in untreated classic disease in males). Cerebrovascular: stroke and transient ischaemic attacks at a young age (white matter lesions on MRI, posterior circulation strokes). Neurological: sensorineural hearing loss and vestibular dysfunction. Gastrointestinal: nausea, abdominal pain, postprandial bloating, and diarrhoea from autonomic gut dysmotility.

Fabry disease is frequently underdiagnosed due to non-specific early symptoms and lack of awareness — average diagnostic delay is 13-16 years from symptom onset. Biochemical diagnosis (hemizygous males): measurement of plasma or dried blood spot alpha-Gal A enzyme activity — activity is severely reduced or absent in classic disease; markedly reduced in late-onset variants. Genetic testing: GLA gene sequencing is required in all cases to confirm the pathogenic variant, guide prognosis, classify as amenable/non-amenable to migalastat, and enable cascade family screening. Females: enzyme activity testing alone is unreliable in heterozygous females due to variable X-inactivation — genetic testing (GLA sequencing) is the diagnostic standard in females. Biomarkers: plasma lyso-Gb3 — elevated in almost all hemizygous males with Fabry disease; less reliably elevated in females; useful for monitoring treatment response. Urine Gb3 measurement. Organ assessment (annual monitoring): renal — eGFR, urine albumin-creatinine ratio; cardiac — ECG (LVH, PR shortening, arrhythmia), echocardiogram, cardiac MRI (late gadolinium enhancement — myocardial fibrosis is a specific finding and adverse prognostic marker); neurological — brain MRI (white matter changes, old infarcts), nerve conduction studies; audiology — pure tone audiometry; ophthalmology — slit-lamp examination; GI symptoms assessment.

Disease-specific treatment: Enzyme replacement therapy (ERT): intravenous infusion every 2 weeks. Two agents approved: agalsidase alfa (Replagal 0.2 mg/kg) and agalsidase beta (Fabrazyme 1 mg/kg). ERT reduces plasma and urinary Gb3 levels, reduces neuropathic pain, stabilises or slows renal and cardiac progression, and may reduce stroke risk — most effective when initiated before irreversible organ damage occurs. Infusion-related reactions (febrile, urticarial) occur in up to 60% of patients — managed with pre-medication (paracetamol, antihistamine, hydrocortisone) and slowing of infusion rate. Migalastat (Galafold): oral pharmacological chaperone that stabilises alpha-Gal A and enhances trafficking to lysosomes — approved for patients with amenable GLA variants (predicted responsive to migalastat based on cell-based assay data). 150 mg on alternate days. Comparable efficacy to ERT for renal outcomes in amenable variants (ATTRACT trial). Adjunctive symptom management: neuropathic pain — carbamazepine (Tegretol) or gabapentin/pregabalin; ACE inhibitors or ARBs for proteinuria and hypertension; antiplatelets for stroke risk; loop diuretics and beta-blockers/anti-arrhythmics for cardiac disease. Renal transplantation for ESKD — Fabry disease can recur in the graft but ERT should continue. Family screening: cascade genetic testing of all first-degree relatives.

Fabry disease causes progressive multi-organ complications that substantially shorten life expectancy in untreated patients. Renal failure: ESKD (end-stage kidney disease) develops in untreated hemizygous males by median age 42 years; renal transplantation or dialysis becomes necessary; ERT slows but does not fully prevent renal progression if started after significant proteinuria or scarring has occurred. Cerebrovascular disease: stroke and TIA at a young age are major complications — Fabry-related stroke is predominantly posterior circulation (vertebrobasilar territory); white matter lesions accumulate on MRI; stroke risk is elevated 12-fold compared with age-matched controls; recurrent strokes cause progressive cognitive impairment. Cardiac complications: left ventricular hypertrophy progresses to systolic dysfunction and heart failure; malignant arrhythmias and sudden cardiac death; AF and heart block requiring pacemaker or ICD; coronary artery disease and mitral valve prolapse. Sensorineural hearing loss is progressive and often bilateral — hearing aids may become necessary; vestibular dysfunction causes vertigo, tinnitus, and imbalance. Chronic neuropathic pain (Fabry crises) causes severe episodic burning pain in the hands and feet, triggered by heat, fever, or exercise — profoundly impairing quality of life, exercise tolerance, school attendance, and employment. Depression and anxiety are highly prevalent, partly secondary to chronic pain, unpredictable crises, and the psychological burden of a rare life-limiting disease. Mortality: untreated classic Fabry disease reduces life expectancy by approximately 20 years in males and 15 years in females — cardiac disease and stroke are the leading causes of death.

Fabry disease itself cannot be prevented as it is a genetic condition — however, early identification through family cascade screening and newborn screening programmes allows treatment before irreversible organ damage. Newborn screening for Fabry disease has been implemented in some countries (Italy, Austria, Taiwan) — identifies affected individuals before symptom onset, enabling early ERT. Genetic counselling: all confirmed patients and at-risk family members (particularly females who may be carriers) should receive specialist genetic counselling and cascade testing. Annual comprehensive multidisciplinary monitoring is essential to detect and manage organ complications: annual renal function and urine ACR, annual echocardiogram and ECG, brain MRI every 2-3 years or after neurological events, audiometry annually, and ophthalmological assessment. Avoid nephrotoxic medications. Aggressive cardiovascular risk factor management (hypertension, dyslipidaemia, smoking cessation) — cerebrovascular and cardiovascular events are major causes of premature mortality. Heat avoidance strategies for anhidrosis. Adequate hydration, regular cool rest, and cooling garments for patients with heat intolerance.

Seek emergency care for: acute stroke symptoms (sudden facial drooping, arm weakness, speech difficulty — FAST), severe cardiac arrhythmia symptoms (palpitations, presyncope, syncope), or severe hyperthermic crisis in a patient with anhidrosis. See a specialist urgently for: diagnosis of Fabry disease in a family member (triggering cascade screening of all first-degree relatives), new or worsening neuropathic pain episodes, rapidly declining kidney function or new proteinuria, new cardiac symptoms or echocardiographic changes, or hearing loss. Any young adult (under 50) presenting with unexplained left ventricular hypertrophy on echocardiogram or cardiac MRI, unexplained stroke or TIA, unexplained renal failure, or unexplained neuropathic pain in childhood should have Fabry disease excluded by biochemical and genetic testing — particularly with a positive family history. Delayed diagnosis worsens long-term outcomes — disease-specific treatment is most effective when commenced early.