Erfan Bashar
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Pompe Disease

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Educational scope notice: This is a study note for medical students, not medical advice, diagnosis, or treatment guidance. Clinical management should follow local protocols and current guidelines.

Pompe disease is an autosomal recessive deficiency of the lysosomal enzyme acid alpha-glucosidase (GAA). Without it, glycogen accumulates most prominently in skeletal, cardiac, and smooth muscle. The diagnosis is established by GAA enzyme deficiency in isolated lymphocytes or mixed leukocytes, by biallelic pathogenic GAA variants on molecular testing, or both.

The infantile cardiac clue

Classic infantile disease presents with prominent cardiomegaly, weakness, and hypotonia. Cardiomegaly and hypertrophic cardiomyopathy are usually identified in the first weeks of life and progress toward left ventricular outflow obstruction with diminished lung volume. When untreated, the disease is fatal in infancy, with death commonly occurring in the first two years from cardiopulmonary insufficiency.

The electrocardiogram adds a clue: a short PR interval with very tall QRS complexes. The short PR interval appeared in 14 of 19 infantile cases in one small historical series, so it supports suspicion without ruling anything out. The working chain is a floppy infant plus cardiomegaly or hypertrophy plus a short-PR ECG pointing at Pompe disease.

CK is supportive, never diagnostic

CK elevation is a sensitive but very nonspecific marker of Pompe disease. The greatest elevation is found in infantile-onset patients, historically as high as 2000 UI/L. That number reflects the assay and era behind it, so it serves as context rather than a cutoff. CK supports the suspicion and never makes the diagnosis.

Confirm with blood enzyme testing plus genetics

Dried-blood-spot GAA testing reaches close to 100% sensitivity for infantile disease, and combined with urinary Glc4 it can effectively rule the disease out. Current practice establishes the diagnosis on blood-based enzyme activity, molecular testing, or both, reserving fibroblast assay for selected cases. Fibroblast culture was the diagnostic gold standard in 2006 but takes weeks to return, so follow the current hierarchy: blood enzyme plus GAA genetics first, with no invasive biopsy required for diagnosis.

Treat early, and check CRIM status first

Enzyme replacement therapy (ERT) should start as soon as infantile-onset or symptomatic disease is diagnosed. Infants treated before 6 months of age and before needing ventilation show improved survival, ventilator-independent survival, reduced cardiac mass, and better motor-skill acquisition than untreated infants. These outcome data are observational against historical controls, so days matter as a principle rather than a measured dose-response.

CRIM (cross-reactive immunologic material) status should be determined before the first infusion. CRIM-negative infants generally develop high-titer antibodies against the replacement enzyme during ERT and need immunomodulation built into the plan early, optimally before the first infusion, which calls for a specialist centre. Testing of all at-risk siblings of any age is warranted so that early diagnosis allows early treatment.

Evidence anchors

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