A twice-missed diagnosis, revealed by the patient history

A 32-year-old woman shows up at the hospital with a range of troubling symptoms, including “fever (102.0), tachypnea, headache, myalgia, dyspnea, peripheral neuropathy, perioral paresthesias tender posterior cervical lymphadenopathy and diffuse, flat, blanching erythematous rash.”

Even more troubling is the fact that her three teenagers all have the same symptoms. The rash started five day before, and the family had been to a rural emergency room twice since. They were initially diagnosed with viral exanthem (a rash caused by a viral infection), then with scarlet fever, for which the antibiotics were not working.

The internal medicine resident who shared this case included this vital detail:

Children later admit to bringing home an “unknown” substance found in a friend’s basement, playing with it, vacuuming it up to clean up the mess they made. 3 hours later, the first rash appeared.

It didn’t take long for Figure 1’s clinical community to follow up on this crucial clue. A young family medicine doctor asked:

A very junior doctor guess, but has mercury poisoning been (or should be) considered?

To which the doctor who posted the case replied:

Although mercury is not common, and poisoning less common, this was mercury poisoning. Kids found elemental mercury in friend’s basement (renting from a dentist who stored it for dental amalgams). The serum mercury level was over 150 mcg/L. The CDC went to the house and found 5x high normal levels 40 ft away from the front door. The vacuum helped vaporize the liquid- increasing absorption. And I only held that back the description of the mercury because they didn’t share that detail on the first 2 ER visits.

Another infectious disease physician brought up an interesting point:

“As I remember from my medical school, elemental mercury is not toxic, but mercury salts and compounds are.”

The resident responded:

“Right, so the different kinds of mercury are absorbed differently. Elemental mercury is only about 9% absorbable in the GI tract where mercury salts are much higher (about 80% if my memory serves). As elemental mercury vaporizes, it is VERY absorbable in the lungs. In this case, the vacuum played a part.”

A family doctor asked why a fever would result from mercury poisoning, to which another medical resident replied:

“Mercury irreversibly blocks enzymes for catecholamine breakdown, causing build-up and subsequent symptoms of sympathetic overdrive — hyperthermia, rather than fever, could be manifested. That would be hard to distinguish on initial exam.”

Ultimately, the correct diagnosis led to a treatment with a chelating agent to remove the metal from the patients’ bloodstreams.

“Pt was in hospital five days, symptoms resolved, and finished the dimercaprol BID x 10 days as outpatient. Her children were cared for by peds and I wasn’t involved with their cases.”