These people have a strange smell of earwax all over their bodies

　　The sweat of these people is fragrant, the urine is fragrant, and even the earwax is fragrant. Others have “body odor”, but they have “body odor”. But because of this fragrance, they need to strictly control their diet for life. Most of them can only live on special milk powder because they suffer from a disease called maple diabetes.
Maple diabetes is not diabetes

　　Maple diabetes is spelled maple sugar-diabetes, which is not a type of diabetes. Maple syrup means that these people’s body fluids, urine, and even earwax have a refreshing sweetness similar to maple syrup. Maple diabetes was discovered more than 60 years ago by American physician John Hans Menkes.
　　In the 1950s, Menkes was a young resident physician. Once, he received a baby who unfortunately died prematurely because various organs “failed”. After questioning the parents, he found that several of the couple’s previous children also died in infancy, and the cause was unknown. But these children all have one thing in common: their bodily fluids all have a sweet and greasy smell.

Fenugreek is a Mediterranean spice

　　These phenomena led Menkes to speculate that the children of this family may have metabolic diseases. Later, he discovered the source of the smell: branched-chain keto acids. Branched-chain keto acids are the products of abnormal metabolism of essential amino acids such as leucine, isoleucine and valine. They will accumulate in human vital organs and brain, causing serious damage and even mental retardation. They are also excreted with urine and sweat, and the concentration of branched-chain ketoacids in earwax is particularly high, so the earwax of maple diabetes patients has a strange smell.
　　Among these branched-chain keto acids, the aroma of trigonelide is particularly prominent. To those who haven’t been exposed to the Mediterranean herb, fenugreek, fenugreek smells more like maple syrup. That’s why Menkes named the newly discovered disease maple diabetes.
　　This unique aroma was also an important criterion for doctors in the past to judge whether a patient had maple diabetes. Now, of course, doctors just need a blood test.
DNA errors lead to ‘sweating’

　　Why can’t these premature children break down those essential amino acids normally? It turned out that there was something wrong with the genes of these children.
　　The substance capable of decomposing the above-mentioned essential amino acids (branched-chain α-ketoacid dehydrogenase complex) is encoded by 4 genes. If one or more of these 4 genes are mutated, the ability to decompose the above-mentioned amino acids will be affected. There will be problems of varying degrees, and the original essential amino acids will become poisons, turning people into fragrant walking corpses.
　　Most of these gene mutations come from the recessive copy carried by the parents, so maple syrup urine disease can be inherited. In the general population, about 1 in every 180,000 babies has maple syrup urine disease, and there are about 2,000 maple syrup urine patients in the United States. However, in some populations with a less mobile gene pool (such as Ashkenazi Jews and Amish), the incidence rate can be as high as one in hundreds of people.

Mendelian inheritance of maple diabetes: Both parents are carriers of the gene mutation (blue) to give birth to a maple diabetes patient (red).

　　Most patients with maple syrup urine disease are diagnosed before the age of 7, and a few develop in adults. In Menkes’ day, most children with maple syrup urine disease, diagnosed in childhood, died prematurely. Modern medicine has extended the lives of these poor children, but they have to abide by a strict diet for life, because ordinary food will kill them at any time.
　　Patients with maple syrup urine disease cannot normally metabolize the three essential amino acids for the human body. These amino acids are called “essential amino acids for the human body” because they are necessary for human beings to live. If you eat too much, you will die, and if you don’t eat, you will die. Three meals a day have become a life and death test for patients with maple syrup urine disease.
　　Because leucine, isoleucine, and valine are high in protein-rich foods such as milk, meat, and eggs, these foods are contraindicated for people with maple syrup urine disease. In order to meet the body’s needs without consuming excessive protein, patients with maple syrup urine disease usually can only eat special foods and cooperate with regular blood tests.
Life-sustaining elixir – special milk powder

　　One such specialty food is formula milk. This type of formula milk powder has decomposed protein into amino acids, and the ratio is strictly according to the needs of the human body to ensure that patients will not overeat.
　　This kind of milk powder is not so much food as a life-sustaining elixir. There are very few companies that can produce this kind of milk powder. For example, in the United States, there is only Abbott. After Abbott was ordered to stop production due to bacterial contamination in 2022, the lives of thousands of patients with maple syrup urine disease in the United States were also seriously threatened.
　　Doctors sometimes give insulin to maple diabetes patients, because insulin can promote protein synthesis, so that excess amino acids that cannot be metabolized in the body will be combined into protein, which will not affect the patient’s body temporarily.
　　Even being careful about what you eat doesn’t guarantee that maple syrup urine disease won’t strike. Maple diabetes will reappear when injured, infected, or under excessive mental stress. Therefore, patients with maple syrup urine must also pay great attention to their physical and mental health.
　　In order to control this rare disease with a small but extremely lethal effect, many countries will carry out routine screening for maple diabetes in newborns. For example, in 2014, the British National Screening Committee announced that every newborn in the UK should be screened for 4 genetic diseases, including maple diabetes. Of course, mothers-to-be can also use DNA pregnancy test to check whether the fetus has maple diabetes.

Protein-rich foods are contraindicated for people with maple diabetes.

　　All in all, “sweet and sweaty” and “farting smells good” are not good things. Their subtext is “serious illness”. DNA needs to do one thing wrong and you will be weird; DNA has to do everything right to make you mediocre.