What Was The Most Amazing Diagnosis You Ever Made? What Was Your "Dr. House" Moment?

This question was originally posted on Quora.com and was answered by David Ryon, Physician leader dabbling in psychology and history



For me, it was my first and last diagnosis of a disease I never knew existed.

Twenty years ago, this middle aged woman had been in declining health over several months, with complaints of worsening fatigue, shortness of breath, and weakness. Finally she was admitted to our ICU after a fainting spell (syncope), with hypotension and changes on her electrocardiogram. This woman had seen her physician several times, and over a period of several weeks had consultations with a Cardiologist, Neurologist, and Endocrinologist, enduring many tests without a diagnosis. Now she was seriously ill with worsening organ function.

While in our ICU, we found she had a subnormal oxygen saturation on the pulse oximeter. Not low enough to explain her symptoms, but abnormal and needing follow-up. The patient had a rather dusky look to her. We did a standard test called ABG, which showed normal oxygen levels.

This discrepancy between her oxygen level and her ability to carry oxygen (blood oxygen saturation) suggests a problem with her hemoglobin. This condition is rare. I was familiar with methemoglobinemia. She didn’t seem to have a reason for that diagnosis, but this was the only diagnosis matching her presentation. Carboxyhemoglobin (COHb) is another hemoglobinopathy, but I was pretty sure that caused falsely elevated pulse ox readings.

Anyhow, the test for methemoglobinemia (metHb), an abnormal methylation of hemoglobin, was negative. I was perplexed. Certainly the result was flawed! I tested for COHb. Negative. The respiratory therapist (RT) collecting the patient’s blood commented on how black it looked. Like Orc’s blood, I thought. MetHb is known to darken the blood. This had to be the diagnosis.

I ordered a repeat MetHb test and met the RT at the laboratory co-oximeter to run the test with him. (Where I trained in medicine we ran the co-oximeter). I was concerned about the machine functioning correctly. As the test was running, a narrow LED digital screen sequentially ticked through and transiently displayed several results that were automatically calculated but not part of my order. One was hemoglobin level. The MetHb level was zero, again.

Then I saw this:

SulfHb 8.5

SulfHb? Sulfhemoglobin, maybe? Never heard of it. The display disappeared. It was not part of the print out. If I hadn’t been standing there, I would have missed it and maybe never would have figured this out.

To the books. Google wasn’t the thing back then. Sure enough, there was a condition called sulfhemoglobinemia. I called the poison hotline for New York City. I had gone to their staff conferences during my medical training at Bellevue, where the meetings were run by Lewis Goldfrank. One of the toxicology fellows helped me through the next steps. We were both learning.

Review of her medications showed she had been prone to urinary tract infections and had been left on a full dose of Pyridium for nearly a year. In addition, she was on cimetidine, an acid-blocking drug that interferes with clearance of drugs like Pyridium. Both of these medications were stopped.

I had a formal test done through a reference lab to confirm the diagnosis. Meanwhile, we started treatment: exchange transfusion. Apparently the sulferization of hemoglobin permanently damages that molecule so that it doesn’t carry oxygen right. So we had to drain several units of her blood and replace it with transfused blood.

She felt better immediately and continued to improve until discharge. I never saw her again. The toxicology fellow wrote up our findings, which were later published here:

Phenazopyridine-induced sulfhemoglobinemia. J Toxicol Clin Toxicol 2002; 40(3):470.

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