Using Smell to Diagnose in Genetic Diseases

Morgan Simmons

A variety of methods are used to diagnose genetic diseases, including physical examination, a review of personal/family medical history, and tests performed in a laboratory. Smells can also be used to make a diagnosis for some genetic diseases.
Smells are caused by small, unstable compounds that activate the olfactory receptors. Interestingly, there are several genetic diseases that prevent an individual’s body from breaking down certain compounds. When those compounds build up in the body, they can create specific scents.
Here are a few genetic diseases known to have an associated scent that can be helpful in establishing a diagnosis:


Trimethylaminuria (TMAU) is a rare genetic disorder that has a distinctive fish-like body odor. The odor occurs when unusually high levels of trimethylamine (TMA) are released in the urine, breath, and sweat. The odor is described as like rotting fish or rotting eggs. The smell may be reduced avoiding foods with high levels of TMA in them.
Maple syrup urine disease
Maple syrup urine disease (MSUD) is an inherited metabolic disorder named, not surprisingly, after the hallmark maple syrup odor of the urine. This unique odor is due to an accumulation of amino acids in the urine. Treatment for MSUD includes dietary restriction of certain branched-chain amino acids. MSUD patients can remain healthy and live through adulthood with treatment.
Phenylketonuria (PKU) is a rare genetic disorder in which people lack phenylalanine hydroxylase (PAH). This deficiency causes elevated phenylalanine levels in the body. PKU patients often have a “mousy” or “musty” odor due to the elevated phenylalanine levels.
Isovaleric acidemia
Isovaleric acidemia (IVA) is a genetic disorder that due to the buildup of organic acids in the body. A “sweaty foot” odor is often present in IVA patients when they are sick.
While these diseases are each associated with a specific smell, it’s important to note they also have other signs and symptoms and require the examination by a geneticist and/or other healthcare providers. 
You can find additional information about these genetic diseases can be found at ThinkGenetic. It may also be helpful to contact a local genetic counselor using the NSGC find a genetic counselor webpage.
About Morgan Simmons – Morgan received her master’s degree in human genetics and genetic counseling from Emory University in 2017 and is currently a genetic counseling fellow at the Emory University Lysosomal Storage Disease Center and a ThinkGenetic contributor.
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