It was the resident’s third or fourth day of no response when someone on the team suggested they consult the metabolic service. Metabolic disorders are disorders that disrupt the processes that convert food into energy at the cellular level. Most of these disorders are inherited – caused by genetic mutations that change the structure or function of one of the body’s tools that are used to metabolize carbohydrates, fats, proteins, and other nutrients. And while most of these diseases are rare, there are many of them. It is estimated that up to 1 in 1,000 people are affected by metabolic disorders. Still, most show up in infancy or childhood, not by the age of 35.
The neurologist called a friend of the metabolism service, Dr. Tyler Peikes, who immediately went to Sean. He checked the records, examined the patient, and received the story from Sean and his family. It didn’t sound like any of the metabolic diseases he knew. The rapid course of the sister’s illness was atypical. He ordered tests to look for diseases that are usually intermittent.
The neurologist kept looking for answers. And slowly the results flowed in. There was no exposure to a metal like arsenic or mercury. It wasn’t an autoimmune disease. It wasn’t an infection. At the end of each day, the resident made another X on her calendar and went home worried. The only hopeful sign was that the patient’s episodes were decreasing. She wasn’t sure why, but hoped they had enough time.
Order the right test
On the 11th day, one of the tests ordered by Peikes finally came back positive. The patient had a rare form of a rare condition called maple syrup urine disease (MSUD). Patients with MSUD are born with abnormalities in the machinery that breaks down certain amino acids, the building blocks of proteins. This leads to the accumulation of unmetabolized protein components that can harm the body. If left untreated, the disease can lead to significant, often fatal, swelling of the brain. The name comes from the smell of maple syrup in urine and sweat, sometimes caused by the build up of amino acids during episodes of protein overload. The patient has never experienced that.
The frequency of a patient’s seizures and the age at which they start depend on how badly the machinery is defective. With intermittent MSUD – the version this patient had – the body can handle low amino acid levels, but a protein-rich meal or severe physiological stress can overwhelm the system and allow toxic components to form. A simple blood test provided the answer. Ultimately, genetic testing showed the specific defect. A subsequent test on Andrea’s tissue revealed the same abnormality. Patients with MSUD must have a low-protein diet. This is the only way to prevent these crises.
It has been more than two years since Sean was diagnosed. He says he misses the occasional steak or burger, but the memory of what happened to him and his sister is enough to keep him away. It was Sean’s family who brought this story to my attention. His mother hoped that by sharing her children’s history, she could help doctors and families consider the possibility of these rare metabolic disorders when patients have a psychiatric or neurological condition that no one can figure out. “It’s not a tough test,” said the mother. “You just have to think about it.”
