This is part of our House MD Project series.

Click here to read the connection to the episode (spoiler alert!)


On episode 15 of season 1, called Mob Rules, a mobster named Joey arrives at the hospital with a coma, from which he comes in and out to repeatedly. It turns out Joey has ornithine transcarbamylase deficiency, a disease causing him to not being able to digest red meat. On a side note the team also discover he has hepatitis C (an infection transferred either by needle sharing or homosexual activity) and that he has a high estrogen level in his blood, caused from a drug used to suppress libido. The last two facts lead house to the conclusion that he is also gay.

Danger level: High

What is it?

Ornithine transcarbamylase deficiency (OTD) is a rare genetic disorder causing a problem with eating protein.

Who gets it?

OTD is a rare condition – it affects about 1 in every 80,000 people. The condition is genetic, meaning it is passed on in families. It also usually happens to males, due to the mode it is inherited.

Usually the condition becomes apparent in the first few days of life. Sometimes, though (like in the House episode), the condition can manifest later in life.

What causes it?

We live and function thanks to millions of reactions that happen in our body each day. One of those reactions happen inside a cycle of reactions called the urea cycle.

The urea cycle. Drawing by Yikrazuul

The urea cycle is a sequence of reactions that happen in our liver cells. It processes excess nitrogen, which is generated when our body uses protein. In order to get rid of the excess nitrogen, the cycle turns it into urea, which the kidneys can get rid of in our urine.

Each of the steps in the cycle happens through the action of a special machine, called an enzyme. In OTD, one of those enzymes is damaged or missing. Since the body can’t get rid of the excess nitrogen, it is accumulated in the body, turning into a dangerous substance called ammonia.

Ammonia is dangerous for our nervous system and so the condition causes neurological problems. The excess can also damage the liver.

How does it feel?

The condition, as we mentioned above, usually becomes evident in the first days of life. The baby will be lacking energy, vomit, or refuse to eat. Its breathing rate and body temperature will be poorly controlled. Sometimes seizures can occur, and even a coma is possible.

In adults the symptoms aren’t very different. They can include loss of appetite, irritability, heavy or rapid breathing, weakness, vomiting, disorientation, sleepiness, and also coma and death. (Remember that the guy on the House episode had recurrent comas).

How is it discovered?

A blood test is done which shows that the person has too much ammonia in their blood. There’s also a test done on a urine sample that can give a clue to the condition.

Also, a genetic test can find out if the person has the defective gene (although it doesn’t work all the time).

How is it treated?

Since the body can’t handle large amounts of nitrogen (it can’t turn it into urea like it normally should), the treatment includes measures that lower the amount of nitrogen in the body.

This includes not eating lots of nitrogen (protein is very nitrogen-rich. That is why a low-protein diet is subscribed. Remember the mobster in the House episode couldn’t eat steaks?).

Treatment includes saying goodbye to steaks. Photo by FotoosVanRobin

Treatment also includes lots of food and water when a person is ill (since otherwise the body tends to break down its own protein at these times) and some medications that can lower the nitrogen in the body.

What happens after treatment?

The baby’s brain can be damaged from the disease (by the ammonia) if not treated on time. It’s important to catch the disease on time, and then to keep with the strict diet throughout life.

The bottom line – How do I avoid it?

As with other inherited diseases, you can’t really prevent it once the person is born with a defective gene. Parents that know they carry the defective gene and can transfer it to their children can use genetic testing to test if the developing embryo has the defective gene (a process called preimplantation genetic diagnosis).

What next?

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