Fabry disease is an X-linked lysosomal storage disorder. Mutations in the GLA gene cripple alpha-galactosidase, the enzyme that degrades glycosphingolipids — lipid components present in every cell — so these lipids accumulate inside cellular organelles. The disease is systemic, but cardiac involvement drives prognosis.
Inheritance and timing
The GLA gene sits on the X chromosome. Males with the affected X chromosome have a very high probability of expressing disease, while females, with a second X chromosome that may compensate, show a wide range from silent to mild forms that ECG and echocardiography can miss. Not all mutations behave alike: classic mutations with severe enzyme dysfunction declare themselves from the second to fourth decade, whereas late-onset mutations with milder impairment accumulate slowly and may surface as late as the eighth decade.
What storage does to the heart
Lipid engorgement inside myocardial cells makes the actin–myosin interaction ineffective, so macroscopic systolic thickening falls. Over years affected cells die and scar replaces them. The result is progressive systolic dysfunction — the main haemodynamic burden, unlike the restrictive course of amyloidosis — affecting both ventricles, with fibrotic scar supplying the substrate for ventricular arrhythmias, syncope, and sudden death. In end-stage disease the weakened muscle cannot generate adequate stroke volume. In untreated late-onset disease, the course from first severe systolic dysfunction to death is reported at roughly 2–3 years.
The imaging signature
Tissue imaging, explained in the cardiac MRI note, gives the characteristic combination:
- Native T1 lowered diffusely across all segments, reflecting intracellular lipid storage. A diffusely low T1 is unusual and narrows the differential sharply.
- Oedema signal minimal — the process is chronic rather than inflammatory, with at most small scattered areas.
- Enhancement midmyocardial and segmental: a pale band sandwiched between darker inner and outer layers, a typical non-ischaemic distribution.
- Extracellular volume raised only where scar sits. Unaffected areas read normal, around 24–28%, because Fabry is primarily an intracellular disease — the extracellular space expands only where dead cells have been replaced by fibrosis.
The mirror image helps memory: cardiac amyloidosis raises T1 and ECV diffusely in every segment, while Fabry lowers T1 diffusely and raises ECV only in scarred segments.
A continuum, not a switch
The signature above is a snapshot, but Fabry tissue injury progresses in stages rather than flipping overnight. Falling T1 appears first, reflecting silent storage with normal oedema imaging and no scar. Oedema follows in some cells, then cell death with enhancement, then progressive fibrosis and systolic decline — and early oedema spatially matches where scar later appears. Treatment started before scar develops may still reverse the process; established fibrosis is irreversible.
Why diagnosis comes late, and why early matters
Recognition often comes late: years of unexplained ECG changes, a moderate coronary stenosis insufficient to explain them, progressive atrial fibrillation, and eventual severe biventricular failure — with Fabry unrecognised throughout. Imaging at the first unexplained ECG change would have shown the characteristic low T1 and prompted genetic testing while function was still normal. Early diagnosis matters for two reasons. Disease-modifying treatment can slow or halt progression before irreversible fibrosis, and every proband, the first patient identified in a family, implies a family: relatives may carry the same mutation, including women with subclinical disease.
Treatment principles
Because the cause is a crippled enzyme, treatment works on the enzyme. Enzyme replacement therapy, available since approximately 2001 with at least two initial products and now a third, supplies functional alpha-galactosidase to clear stored lipid. Chaperone therapy works differently: it stabilises the patient’s own misfolded enzyme so it functions more effectively.
Screening the family
Once a proband is diagnosed, at-risk relatives merit screening. Male relatives carrying the mutation are likely already expressing disease. Female relatives need particular attention: X-inactivation, the chance silencing of one of the two X chromosomes in each cell, decides severity, so a normal ECG and echocardiogram do not exclude carriage — genetic testing and tissue imaging reveal subclinical disease.