Developmental Delay Can Precede Neurologic Regression in Metachromatic Leukodystrophy

Pompe disease is an inherited lysosomal disease in which there is a decrease or absence of acid alpha-glucosidase activity. This enzyme defect induces glycogen storage in different tissues, especially muscle and heart, resulting in muscle weakness, respiratory failure and heart disease. Substitutive enzyme replacement therapy (ERT) dispensed every two weeks is the only treatment that has shown benefits. However, this treatment induces hypersensitivity for half of the treated patients. Reactions range from mild to severe, sometimes requiring ERT suspension and anti-anaphylaxis drug administration. Understandably, high amount of acid alpha-glucosidase infusion seems to be identified by the immune system as a danger associated molecular pattern, and induce an immune reaction, involving sometimes, but not always, immunoglobulin E (IgE) production and activating mast and basophil polynuclear cells. Considering the lack of therapeutic alternatives and the proved benefit of ERT, desensitization finds its place here. We hereby report the case of a patient for whom a simplified desensitization protocol (“SWORD”: Start With One Regular Drop) was successfully achieved, allowing ERT to be pursued, resulting eventually in clinical improvement.