Researchers at the Sahlgrenska Academy have discovered a previously unknown congenital disease that is caused by a genetic defect resulting in muscle cells not being able to store energy from sugar. In the worst case, the disease can lead to the heart stopping.
The researchers have identified three sisters who have a previously unknown disease that affects the heart and muscles. The oldest child, who was being treated for epilepsy, did not have the energy to play as much as her friends, but in general was considered to be a normal child. At the age of 10 the child died suddenly while playing in the school playground. The post-mortem examination noted that the cardiac muscle was enlarged - a condition that can result in impaired circulation and lead to heart failure.
When one of the younger siblings displayed similar symptoms a specimen of the child’s muscle tissue was taken. It revealed that the muscle lacked glycogen, one of the major sources of fast energy for muscles.
Glycogen consists of long sugar chains that are manufactured and stored in the cells. When the cell requires additional energy the sugar chains are cut into pieces and form glucose. As the heart is a muscle that never rests, it is in constant need of energy. When it is under strain it has to derive additional energy from glycogen.
The disease is rare. A genetic analysis of 100 people in the population group revealed that one was a carrier. Two carriers are required for the disease to develop.
The discovery that people can live without glycogen can also be of great significance for research into other conditions, among others diabetes type 2, where one theory is that reduced formation of glycogen in the muscles is the cause of reduced insulin sensitivity and increased blood sugar.
The study is presented in the medical journal, New England Journal of Medicine.
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