Johns Hopkins Magazine - April 1996 Issue

Dear Dr. Zebra

By Elise Hancock, Adapted from Flashcards and research by John Sotos
Can run but can't walk
Dear Dr. Zebra: My son is a 19-year-old college student who sometimes gets severe pain in his left calf, just from walking around. But he can run perfectly well--he plays on the basketball team. In fact, running helps the pain.

Mike's doctor thinks he's overusing the leg, because when he rests for a few days, the pain goes away. But I'm worried, because the pain is worse every time it comes back, and this morning his left toes were pale and cool.

Mrs. Fran Tick*
Bedford, Indiana

Dear Mrs. Tick: I suspect your boy has an inborn anomaly involving the popliteal artery, the one running behind the knee, down through the calf, and into the foot. In a few people, most often males, the artery is so placed that the calf muscles can squeeze it shut whenever the foot bends. The reason it hurts your son to walk but not to run is that running squeezes the artery much more briefly than walking. Some experts think this problem shows up more readily in athletes because their muscles are more developed.

The symptoms are unusual, because most young athletes can tolerate prodigious amounts of exercise. Also, with a problem that restricts blood flow, you'd expect vigorous exercise to be more painful than walking. Only 300 some cases have ever been reported, and non-specialists may never have heard of it.

Fortunately, it sounds as if your son is still at an early stage, because as blood flow gets worse, any exercise hurts. Check it out with an orthopedist immediately. If the problem is caught early, a surgeon can simply snip the noose of muscle around the artery, setting it free. Left untreated, your son could develop gangrene.

And make sure the doctor checks both legs: in about one-quarter of cases, both are affected.

The ring-shaped rash
Dear Dr. Zebra: A patient of mine came back from Japan with an extremely odd rash, a large swollen ring around his buttocks that itched fiercely. He'd already been using calamine lotion and it seemed to help, so we stuck with that and just added steroid cream. The condition cleared right up. What was it, though?

Derry Ayres, MD
Lawrence, Kansas

Dear Dr. Ayres: Some things really are caught from toilet seats, including your patient's rash. My hunch is that he has a history of reacting to poison ivy, oak, and sumac, like about half of Americans--which would make him sensitive to a lacquer the Japanese sometimes paint (you guessed it) on toilet seats.

The lacquer is made with resin from a tree related to poison ivy, oak, and sumac, and they all contain urushiol, poison ivy's itchy agent. Other members of the family include the cashew, pistachio, mango, and gingko trees.

In their own countries, Brazilians are seldom bothered by mango rind, nor Japanese by dry lacquer, because they have not been exposed to poison ivy, oak, or sumac. These three natives of North America seem to have an amazing ability to irritate the immune system into red alert. Then once people are sensitive to "leaves of three, let it be," they cross-react to its milder cousins.

Hence your patient's troubles, and also the clown-like "Florida grin," caused by chomping mangos in the rind. In 1982, 54 people in rural Pennsylvania burst out with what looked like poison ivy all over their bodies, after eating improperly processed cashew nuts from Little Leaguers; the nuts were contaminated with oil from the shells.

Concerning urushiol, the latest medical discoveries remain low-tech: If you're exposed, wash the skin quickly and thoroughly with plain old water. Barrier lotions may help prevent exposure.

Sometimes I smell like a fish
Dear Dr. Zebra: I wash all the time, but the other kids say I stink like rotten fish. They make up rhymes about me and nobody will eat lunch with me. Nobody will sit beside me on the bus. It makes me cry. I take baths all the time. I used to scrub myself with a scrub brush until my mother found out. Sometimes it's okay, but then I stink again. I cry a lot, because nothing helps. Even my grandma says I don't wash right. Sometimes I would like to crawl under my bed and never come out. What can I do?

Please don't use my real name.
"Hal" from Denmark, South Carolina

Cheer up, Hal--I am almost certain the problem is something you eat. If that's right, the smell will go away as soon as you stop eating those foods.

To find out, your doctor should test you for trimethylaminuria, which is a long way to say that when you eat fish, eggs, liver, kidney, or soybeans, your body does not digest these things quite the way other bodies do. These foods have a chemical called choline (say it like KO-leen), which germs in the gut digest into trimeth-ylamines (just call them TMA). TMA smells fishy--very fishy, in fact.

For most people that fishy smell doesn't matter because their body turns TMA into something else, TMA oxide, which does not smell at all. But in people with trimethylaminuria, their bodies cannot change the TMA. So the TMA comes out in their sweat, urine, and breath, and no matter how much these people scrub, the TMA makes them smelly. Having this problem does not make people sick in any way, but it certainly is embarrassing.

You say that sometimes the fishy smell goes away, which makes me think that if you stay away from foods with choline, you'll be fine. The worst foods for you would be fish, eggs, liver, and kidney. Avoid them. If that's not enough, then you should also stay away from soybeans, peas, and mayonnaise. (Think of that--a doctor's excuse not to eat liver and tofu!)

Eggs, soybeans, and mayonnaise can be hard to avoid, because they are part of many packaged foods. At first, you'll have to think a lot about things like whether a Big Mac has mayonnaise (it does). You and your family will have to read the labels on packages very carefully. But you'll soon learn what you can and cannot eat.

This diet is a pain, there's no doubt about that. But it's much less of a pain than smelling like rotten fish.

Am I crazy?
Dear Dr. Zebra: My neighbors were plenty worried when the nearby military airfield expanded, but the prospect of added noise did not bother me. Boy, was I wrong. The problem, however, is not jet noise (the sound of freedom), but a high-pitched buzzing sound, like a bee, about three feet over my head. I hear it whenever I'm in the back yard. Only there's never any bee, and the noise follows me all over the yard.

My wife can't hear it and my doctor keeps asking me about stress and my mood and, lately, whether there are voices, too. Am I crazy?

D. Feaht, EdD
Rancho Mirage, California

Dear Dr. Feaht,
Maybe, but let's consider some other possibilities. Do you have a malfunctioning hearing aid or cochlear implant? Some have been known to deliver radio broadcasts straight into their wearers' ear.

Or--since you live near a military airfield--could the cause be some secret weapon? There is a precedent. In the Stealth Fighter's early days, civilians near Edwards Air Force Base noticed that their dogs would start barking just before one of the black jets passed overhead. Apparently worried by the possibility of an enemy with a canine-based early-warning system, the Air Force then modified the jet engines to make them dog-quiet.

The most plausible non-hallucinatory explanation may be that your backyard is bathed with radar waves. Radar was heard as early as World War II, at power levels well within those considered safe for human exposure.

You can "hear" radar because the small pulses of energy delivered by these electromagnetic waves cause a minuscule but rapid rise in the temperature of your brain. That makes the brain expand a bit, which results in a pressure wave inside your skull that is conducted via bone to the ear. Sometimes people hear clicking or hissing, depending on the frequency and shape of the pulse. Your wife should have her hearing checked.

"Yeah, Doc, the whole family's got this flu."
Dear Dr. Zebra: I would like to share with you an observation that may be helpful to other physicians: In the winter, if an entire household suffers from headaches, dizziness, and vague malaise, the problem could be carbon monoxide poisoning, not the flu.

That may be especially true in my practice, which is predominantly inner-city. About half these people augment the landlord's heat by running their gas stoves, door open. But cooking stoves aren't designed to work that way, so incomplete combustion--producing CO [carbon monoxide]--can result. Any heating source that flames could be at fault, however. I recommend a high index of suspicion to all physicians.

C. O. Hebb, MD
Baltimore, MD

Dear Dr. Hebb: You are exactly right, and I'm very glad you wrote. "Disease often tells its secrets in a casual parenthesis," as the English neurosurgeon Wilfred Trotter said.

It is good practice to ask about a patient's source of heat and whether anyone else is sick, and to always, always, always keep the possibility of carbon monoxide in mind. Even though deaths from CO have dropped each year since the Clean Air Act, it remains a leading cause of death by poisoning in the United States. Unintentional exposure to the gas kills about 800 people each year, and makes another 10,000 miss work or see doctors each year--and those are only the cases we diagnose and know about.

Inexpensive CO monitors for the household are now available. Let's hope they soon make a dent in these numbers.

Meanwhile, both doctors and the public need to know that the famous cherry-red skin we used to expect turns out to be unusual (at least in the early stages). Instead, look for headache, dizziness, weakness, nausea, "trouble in thinking," and difficult breathing. Body temperature may be up, and diarrhea is not uncommon.

It's easy to see why viral illness and food poisoning are common misdiagnoses. Then patients are sent back home to the place that is making them sick.

Even very low levels of CO can cause chest pains or breathlessness in smokers, lung patients, and people with coronary artery disease. Because the supply of oxygen flowing to their hearts is already tenuous, the CO in the air on a polluted day is enough to cause problems.

It also matters where in the house patients sleep and spend their time. There have been several tragic cases in which a plugged-up furnace flue went unnoticed till a grown child came to visit, worried about his vaguely ill parents. The parents came downstairs in the morning to find their child dead in the living room, just above the furnace.

CO-laden air can also be found in boat cabins; near open cans of paint-stripper; near freeways; at indoor stadiums used for tractor pulls, mud races, and monster-truck jumps; and at a few ice rinks. In 1989, a skater nearly died after long practice in a poorly ventilated rink. It turned out that the rink's Zamboni, the machine used to shave ice clean for the skaters, was out of repair and spewing CO.

"Not tonight, dear.
I'm allergic."

Dear Dr. Zebra: I heard about a woman who collapsed and nearly died the first time she had sex. How could that happen? Does it happen very often?

Deborah Deere
Dallas, Texas

Dear Ms. Deere: You seem to have heard about a severe allergic reaction to semen, which is so rare it makes no sense to worry. (There are lots of more likely hazards from sex.) Such reactions to first intercourse are reported only about once every 10 years, mostly in women with a history of other allergies.

It is true that allergic reactions may be exaggerated if they're triggered via sex. Mucous membranes (such as the mouth, rectum, and vagina) are so richly supplied with blood vessels that the allergen goes quickly and directly into the bloodstream. A reaction can come on slam-bang, sending the body into shock as you describe.

The puzzling part is that nobody is allergic to anything the very first time. First the immune system must be exposed to the allergen, and then it must have time to gear up and manufacture antibodies. So exposure there must have been, if not to semen then to something very like it.

Most often, allergies to sex develop over time and are less scary. For example, a couple in Boston got into trouble two years after beginning intercourse. The wife's vagina would swell, itch, and burn most miserably, until an allergist was able to desensitize her. The couple then had to have sex at least every 48 hours to prevent the allergy from coming back. They could honestly say it was what the doctor ordered.

Sometimes women react not to semen itself, but to chemicals it carries. In a recent case report, a woman suddenly began to get a swollen, painful rash every time she and her boyfriend had sex. It turned out he was taking dicloxacillin, a form of penicillin--to which the woman is allergic. Even though the amount of drug in his semen was too small to measure, it was enough to create a problem.

Our newest concern in this regard is latex, a commercial form of rubber. Most condoms are made of latex, and for reasons we don't understand, the number of latex allergies has been rising sharply since the late 1980s. Occasional patients now react badly to their surgeon's gloves, despite having no known exposure to latex. And in 1989, for the first time, a few patients went into shock while receiving barium enemas, due to latex balloons on the catheters. (The devices were immediately discontinued.) One died. So latex in the body or on mucous tissues can be dangerous.

Do not, for goodness sakes, take this warning as a doctor's excuse not to use condoms. Diseases like AIDS and drug-resistant gonorrhea are the bigger threat.

You have doubtless been told that abstinence is the safest bet of all, and that's true. If you choose to have sex, however, remember that the risk of disease far outweighs the risk of an overwhelming latex allergy. Use a condom.

But be alert for early signs of latex allergy. Do elastic waistbands, latex gloves, or blowing up balloons make you itchy? Do you react to bananas, avocados, kiwis, and chestnuts? (These allergies predict problems with latex, because the trees are related.) Do you live or work near a highway, where aerosolized rubber from tires is in the air? Are you sniffly all the time? Are you prone to allergies in general?

If so, it makes sense to be cautious about latex near your mucous membranes. You should talk it over with your doctor.

Flashlight-packing Momma
Dear Dr. Zebra: The other day my daughter, Mary, was complaining about a sore throat, so I hauled out the flashlight to take a look. And while I was looking I noticed that her fillings stick out on the inside, the tongue side. What on earth could cause that? We just finished spending a lot of money on her braces.

Ima Worre
Glenside, Pennsylvania

Dear Ms. Worre: Mary's braces probably have nothing to do with it, I'm sorry to say. Please sit down and take several deep breaths before you read on, because the news is not good.

Fillings that project above the surface of the teeth are caused by acid in vomit. They are therefore a likely sign of bulimia, the disorder in which people force themselves to vomit in order to control their weight.

You might also look at Mary's hands, especially around the knuckles, because at least at the beginning, a person with bulimia must put a finger down the throat to trigger reflex vomiting. Their knuckles often show scars or callouses where teeth hit skin.

Fillings resist acid better than teeth, so the teeth slowly erode and leave the fillings poking out, especially (as you noticed) on the tongue side. The teeth themselves will be extremely smooth and free of stains.

It takes about four years of vomiting three times a week or more to develop this sign, so I would urge you and Mary to seek a professional evaluation immediately. Bulimia upsets the body chemistry and can be fatal. Make sure she sees a psychiatrist with extensive experience in eating disorders.

The preferred treatment starts with time as an inpatient, on a unit where nurses will watch Mary night and day to prevent her vomiting. This rigor is helpful because advanced bulimics can seldom simply stop vomiting by an act of will. Most feel humiliated beyond words and have already tried to stop. The vomiting becomes a compulsion, and patients may feel overwhelming panic when they cannot get the privacy to do it.

On the plus side, treatment usually helps, over time. This disorder is not uncommon, especially in young women, and doctors have considerable experience with it. It may help you to know there is a physical component, so that patients often respond to antidepressants. (Indeed, many are clinically depressed as well as bulimic.) I will hope to hear from you after some months that Mary is back in school, eating normally, and happier than she's been in years.

Teeny-tiny handwriting
Dear Dr. Zebra: In the last year, my older sister's handwriting has become so small and so sloppy that I can hardly read her letters. I haven't seen her since she moved to Florida after retirement, so I don't know if anything else is odd, but I'm concerned. She insists she's fine. What do you think?

Percy P. Cassius
Bath, Maine

Dear Mr. Cassius: I'd suggest you go for a visit, or somehow find out a bit more about your sister's condition. Be alert for problems with movement.

I say that because some healthy people write in miniature all their lives--Emily Bront‰'s handwriting was almost microscopic. But when it comes on as a change, the only reasons I can think of are neurological.

We call the condition "micrographia," and among other things it occurs in Parkinson's disease. Hitler had this symptom in his last years, a fact that was used to help determine that the Hitler "diaries" found in the early 1980s were a hoax.

Two other causes of micrographia are stroke confined to certain regions of the brain and a condition in which people see everything as larger than it is, including their own handwriting.

If your sister is open to suggestion, you might ask her to write on a child's double-lined notepad, shaping each character to fill the space between the lines. In 1921, French researchers found that double lines helped a Parkinson's patient move from characters one-quarter of a millimeter high to something that people could read.

And finally, Dr. Zebra's pop quiz
Dear reader: To what do you attribute the following?

A. In a 24-year-old Asian male, flaccid paralysis after eating a big spaghetti dinner.

B. Patient eats a 16-oz. New York steak, then cannot move.

C. Red urine after eating beets, as a new or sometime trait.


A. Thyrotoxic periodic paralysis, a rare complication of hyperthyroidism. Possibly for genetic reasons, it is most often seen in Asian males; high carbohydrate intake brings on the attack. The paralysis can also appear during sleep or rest after prolonged exercise; the patient wakes up unable to move or walk. Indeed, muscles don't even respond to direct electrical stimulation. Patients recover completely as soon as the hyperthyroid condition is corrected.

B. Patient is taking L-dopa for Parkinson's disease, the "shaking palsy." His medication has stopped working because amino acids from all that protein in the dinner pre-empted spots on the "neutral amino acid transport system" that moves L-dopa through the blood-brain barrier.

C. "Beeturia" is the technical term, and its appearance probably means the patient is iron-deficient. When 100 grams of small beets ("much more than anyone would eat from free choice") were fed to patients with untreated iron deficiency anemia, 80 percent developed beeturia. Of 15 similar patients after treatment, only one showed red urine. Iron and beet pigment appear to compete for the same intestinal "acceptors," with iron preferred. The pigment is accepted--and therefore appears in urine--only when the intestine has to make do. That is, when the body is iron-hungry.

--Dr. Z

The man behind "Dr. Zebra"
Cardiologist John Sotos (MD '83) emphasizes that he is not really Dr. Zebra: "I just know a lot of weird stuff." Nor does he practice medicine. "I think medicine is like flying. Unless you do it all the time, you're dangerous. I have no desire to be dangerous."

Instead, Sotos lives in Baltimore and develops what he calls "insanely great medical software." His biggest project at the moment is an NIH-supported expert system that will deliver personalized information to lay people about preventive medicine. "Patients are much more motivated to do preventive care than doctors are," says Sotos. "Doctors are too busy putting out fires."

He believes that many medical programs err by leaning on general rules. "My software is designed to keep track of very small subgroups of people who need different approaches." For instance, one general rule says preventive sigmoidoscopy should begin at age 50. "But if your Dad and Aunt Irene and their dad all died of colon cancer, you should start colonoscopy at age 40, and in some cases even earlier. And that's the sort of thing my software will do. That will, I think, help more people than I could ever help by seeing one person at a time." Sotos expects to release the program within a year.

As for the flashcards this article is based on, that enterprise began in Sotos's days as a medical student at Hopkins, when he started files on medical oddities. The resulting collection of "Zebra cards," a set of 201 improbable clinical scenarios, is available from the American College of Physicians in Philadelphia, 1-800-523-1546. To reach Sotos himself, e-mail

Sotos still wears his Osler tie on Fridays, that is when Friday coincides with "one of the very few days that I wear a tie."

Send EMail to Johns Hopkins Magazine

Send EMail to Elise Hancock

Return to table of contents.