A 2 year old girl with normal birth and development came in with the history of inability to get up from squatting and difficulty in climbing stairs for the past 4 months. She had no muscle pain or tenderness and no calf muscle hypertrophy. Her CPK was 700 ugm/L and LDH was 1394 U/L, both moderately elevated.
Her EMG was myopathic. Her workup for autoimmune myositis was negative. However her DBS screening for Pompe's disease showed low levels of acid alpha glycosidase (GAA). We decided to do genetic studies to confirm the diagnosis.
Late onset Pompe's is often not in our radar for children presenting with proximal myopathy.
What are the clinical clues to trigger its consideration in a clinicians mind?
It predominantly affects the hip girdle muscles such as the hip adductors and flexors.
A peculiarity is the involvement of the paraspinal muscles. Sometimes they have back pain or a rigid spine. Myotonic discharges from the paraspinal muscles are considered a good clue to the diagnosis.
The relative involvement of the diaphragm and accessory muscles of respiration results clinically in recurrent pneumonias. Nocturnal hypoventilation may present as early morning headaches. You can check for a decline in oxygen saturation and FVC ( > 10% fall) in the supine position which is a good screen for diaphragmatic involvement.
Unlike the classic Pompe's disease the heart is not involved except for stray reports of WPW syndrome.
Neither do they have hepatomegaly or macroglossia.
Enzme levels range between 1-40% of normal.
Most importantly early use of enzyme replacement makes a significant difference in what would otherwise be progressive decline in muscle function. https://www.aanem.org/mxonline/resources/downloads/products/ED01.pdf
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