Amazing Medical Conditions: Maple Syrup Urine Disorder

If you were to be diagnosed  with the condition known as maple syrup urine disease you may think that you’ve hit the medical jackpot: All the free maple syrup you can drink at your disposal almost anytime. But you would be wrong, friend. Despite its quasi-pleasant name, MSUD — that actually is the medical term — is actually a dread disorder of the metabolic system that can cause all manner of grievous harm, like brain damage, coma and cognitive disabilities. They don’t call it maple syrup urine disease for nothing, though. Thanks to the buildup of the three members of the branch-chain amino acid family — leucine, isoleucine and valine — the urine of people with this condition can frequently smell of maple syrup.

You could say that the branch-chain amino acids are perhaps overlooked by the public at large. They play a big role in building muscle and burning fat and they’re essential acids, meaning we have to ingest them; we need them but our bodies can’t produce them. The trouble with MSUD is that people with the condition lack the protein that the body produces  to break the branch-chain amino acids into useful (and not deadly) forms. Without this protein, the three acids can build up in the body and period of stress, even fairly simple or typically innocuous types, like a fever or a prolonged time between meals, can have life- and mind-threatening consequences.

Maple syrup urine disorder is a genetically inherited autosomal recessive disorder, which means that both copies of each of the four genes that make the protein that breaks down the leucine and its friends must all bear the mutation that prevents synthesis of the protein. This makes it relatively rare, affecting about 1 in 185,000 live births. It’s far more prevalent among Old Order Mennonites, a Swiss religious sect that migrated to Pennsylvania in the 18th century and suffered a population bottleneck as a result. It shows up in about 1 out of 358 Mennonite infants.

It’s a plus in the case of MSUD that our bodies don’t make branch-chain amino acids; at least the body isn’t poisoning itself — it just can’t break these proteins down. And since branch-chain amino acids have to be ingested to be introduced into the body, treatment for MSUD amounts mainly to observing a strict, lifelong low-protein and no-branch-chain diet and keeping the body out of stress like infections and fevers. There’s also the potential for treatment through a liver transplant: Since the process of breaking down branch-chain amino acids takes place largely in the liver, a healthy donor without MSUD should have enough protein stored to allow the recipient to effectively be cured of the disorder.  So far, three successful liver transplants have  been carried out to treat MSUD.