In 1954, a tragic event unfolded when four infants belonging to the same family passed away within their first 90 days of life. Medical professionals investigating the cause of death identified a neurodegenerative disorder as the culprit. Interestingly, all four babies exhibited a peculiar symptom – their urine emitted an odor reminiscent of burnt sugar. This unique condition is known as Maple Syrup Urine Disease (MSUD), an incredibly rare genetic disorder stemming from a defect in the breakdown of specific amino acids, namely leucine, isoleucine, and valine. Soon after birth, the distinct scent of maple syrup becomes noticeable in the affected individual’s urine, and in some cases, even in their earwax and sweat. Failure to treat MSUD promptly can lead to severe complications such as neurodegeneration and encephalopathy.
Causes of Maple Syrup Urine Disease
Maple Syrup Urine Disease (MSUD) is caused by mutations in the BCKDHA, BCKDHB, and DBT genes, according to researchers. These mutations result in a catabolic defect that leads to the development of the disease. As a consequence, three amino acids accumulate in the body, along with their toxic byproducts or keto acids. This build-up of substances can cause metabolic acidosis, a condition in which the kidneys are unable to adequately remove the excess acids.
Studies have indicated that MSUD affects approximately one in every 185,000 people. However, the occurrence of the disease is higher in certain ethnic groups. For instance, in the Ashkenazi Jewish population, the condition affects about one in every 26,000 live births. On the other hand, in the Mennonite population, the rate of MSUD is as high as one in every 380 individuals.
Classic Maple Syrup Urine Disease (MSUD)
Classic Maple Syrup Urine Disease (MSUD) is one of the subtypes that most individuals with MSUD fall into, although there are some cases that do not match the defined protocols. This particular subtype is typically evident within the first few days of birth. Babies with classic MSUD have difficulties feeding from either the breast or bottle. Without the necessary nutrients, the child becomes irritable and lethargic. As the condition progresses, the baby may exhibit neurological signs such as athetosis, which involves slow and convoluted writhing movements of the digits, limbs, neck, and tongue. These movements may then develop into hypertonia, where the muscles become rigid even when at rest. In severe cases, the child may experience spasms, convulsions, and eventually fall into a coma. At a certain point, the condition can lead to neurological and respiratory failure, which become inevitable.