Table 2.

Clinical Considerations for Evaluation of Cause

HistoryDevelopmental delay or regression
Poor growth or failure to thrive
Feeding difficulties or intolerance
Metabolic decompensation with illness
PhysicalDysmorphic features
Short stature
Vision or hearing loss
Hypotonia or hypertonia
Gait abnormalities or muscle weakness
Congenital anomaly
LaboratoryUrine organic acids, serum amino acids, acylcarnitine profile, lactate, pyruvate, creatine phosphokinase, enzyme testing for concern of Pompe
Sequence-based genetic testing (eg, cardiomyopathy panel testing, Noonan syndrome testing, mitochondrial panel)
Directed biochemical (eg, urine glycosaminoglycans, transferrin isoelectric focusing), genetic (eg, muscular dystrophy panel), or invasive testing (eg, muscle biopsy) based on initial laboratory results