However, IOPD signs and symptoms vary and experts have classified IOPD into two forms, classic and non-classic:
The classic form of IOPD, also known as “typical”, is characterized by an enlargement of the heart (cardiomegaly) which occurs within the first few days to months of life.
The non-classic form of IOPD does not typically present with heart problems or cardiomegaly as severe as in classic IOPD, and a broad range of signs and symptoms have been reported, making its diagnosis more difficult.
Pompe disease predominantly affects the muscles. Signs and symptoms of IOPD typically arise from deficiencies in the muscles that make breathing possible, pump blood, and allow mobility. The most common signs and symptoms are described below. For a more comprehensive description you may consult the signs and symptoms of IOPD checklist.
An enlarged heart, due to thickening of the heart muscle (hypertrophic cardiomyopathy), is the classic sign of IOPD, and may lead to the heart having a decreased ability to pump a sufficient amount of blood to the body. The heart’s “electrical wiring” (conduction system), can also be affected in IOPD, which can result in disturbances in the rate and rhythm of the heart.
The muscles used in breathing may be affected in IOPD, hence infants may have difficulty supplying oxygen to the body and must make a greater effort to properly inhale and exhale. Breathing issues such as respiratory distress, sleep-disordered breathing (sleep apnea), and even respiratory failure are possible. As the muscles used for breathing may lose strength, a weak cry and a wet cough can also occur in IOPD. Frequent “colds” (upper respiratory infections) and bouts of pneumonia can also be related to these breathing difficulties as patients may not be able to cough and properly clear secretions.
Lack of muscle tone (hypotonia) resulting in muscle weakness (myopathy) is common in babies with IOPD. Infants with IOPD can be described as having “floppy baby syndrome.” This muscle weakness can be found throughout the body, but it typically affects muscles closer to the body’s midline (proximal muscles). Because of the muscle weakness, delays in reaching developmental milestones, such as head control or independent walking, can also indicate IOPD.
Infants who are not gaining weight according to expectations could have Pompe disease as an underlying cause. Impairments in sucking, feeding, and swallowing occur in IOPD, and contribute to this lack of appropriate weight gain. An unusually large tongue (macroglossia) may occur in IOPD and can interfere with appropriate weight gain. An enlarged liver (hepatomegaly) has also been observed in IOPD.