Pompe disease is an autosomal recessive storage disorder caused by a deficiency in the enzyme α-glucosidase, resulting in intralysosomal glycogen accumulation in skeletal and cardiac muscle. The classic infantile form is characterized by progressive hypertrophic cardiomyopathy, hypotonia and macroglossia with onset during the first months of life. The article reports on the case of Y., a newborn who presented with hypertrophic cardiomyopathy and who was diagnosed with Pompe disease within the first 14 days of life. The case emphasizes that a cardiomyopathy present in the first days of life, even in the absence of hypotonia, can be a signal for Pompe disease. An early diagnosis is crucial because it allows the introduction of enzyme replacement therapy and leads to a better outcome. The enzymatic analysis on drop blood sample is a quick, minimally invasive and easy method applicable to a newborn with cardiomyopathy of unknown origin.