Neurophysiological findings are important to assess the severity of Pompe disease  (PD) and motor neuron damage in all pediatric patients, according to a new study published in the journal Molecular Genetics and Metabolism. Therefore, motor nerve conduction studies should be systematically performed in all children with the disease.

A team of researchers analyzed concomitant clinical motor outcomes and electroneuromyography findings in 29 patients with infantile-onset PD and juvenile-onset PD. 

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Of those, 20 who survived underwent neuromotor studies. Twelve had infantile-onset disease, 4 had juvenile-onset disease, and 4 received enzyme replacement therapy (ERT) in the first month of life.

The results of motor nerve conduction studies were primarily normal. 

Needle electromyography that was performed at diagnosis consistently showed that myopathy responded to ERT. 

A total of 2 patients with infantile-onset PD had mixed motor neuropathy and myopathy, a poor outcome, and never walked. 

One patient with infantile-onset disease and 1 who received ERT during the first month lost the ability to walk when they were 9 and 3 years of age, respectively. The researchers also reported that 1 patient with juvenile-onset disease was about to lose the ability to walk due to the development of motor neuropathy, which usually occurs in patients who are at least 10 years of age. 

“Initial or secondary motor neuron involvement seems to be associated with a poor motor outcome showing that ERT may fail to prevent the accumulation of glycogen in motor neuron[s],” the researchers concluded. 

Pompe disease is a rare genetic disease caused by a mutation in the gene encoding for the lysosomal acid alpha-glucosidase (GAA) enzyme, which cleaves glycogen to form glucose. The mutation causes the enzyme to malfunction and glycogen to accumulate in different tissues, mainly heart and muscle tissue, leading to damage. 

ERT aims to provide the body with functional GAA enzymes.

Reference

Brassier A, Pichard S, Schiff M, et al. Motor outcomes in patients with infantile and juvenile Pompe disease: lessons from neurophysiological findings. Mol Genet Metab. Published online July 14, 2023. doi:10.1016/j.ymgme.2023.107650

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