What Caused This Patient’s Blood to Turn Brown?

After a tweet with an image of brown blood smeared on a piece of gauze caught the attention of thousands on #medtwitter, its author hopes it offered a teachable moment — and potentially made physicians aware of a worrisome trend.

In early June, a 13-year-old boy presented to Papa Giovanni XXIII Hospital in Bergamo, Italy, with a headache and severe cyanosis. He was ambulatory, had a normal heart rate and blood pressure, and was without fever, according to Giacomo De Luca, MD, a resident at the hospital, who posted about the anonymized case on social media.

The patient wasn’t short of breath, but he had an oxygen saturation of about 80%. Despite that, he didn’t respond at all when breathing in 100% oxygen. His heart and lung ultrasound was normal.

When his blood was drawn, it was brown — a key feature of methemoglobinemia. Indeed, testing revealed the patient had a sky-high methemoglobin (MetHb) level of 48.5%.

After consulting with toxicology, De Luca and team initiated methylene blue at 1 mg/kg over 5 minutes, and the patient improved immediately, with his MetHb levels falling rapidly.

He was admitted to the hospital while the team searched for a cause.

De Luca posted the case to Twitter, to highlight what he found suspicious so that others facing a similar challenge could resolve it quickly.

Notably, the lack of response to 100% oxygen in the face of an 80% saturation was suspicious; methemoglobinemia renders pulse oximeter readings inaccurate, he said. The condition also “causes chocolate-brown discoloration of the blood. If blood is dropped on a piece of white gauze, it will remain brown as it dries,” De Luca told MedPage Today via email. It can also cause cyanosis or brown/grey discoloration of the skin, he said.

“Through discussion with other colleagues all over the world I became aware of many potential causes of methemoglobinemia, such as some illicit drugs (e.g., poppers). Our young patient strongly denied use of drugs,” De Luca wrote in the email.

De Luca also “became aware of some recent fatalities due to sodium nitrite toxicity in Italian youngsters thanks to the reporting of some toxicologists who followed my case on Twitter.”

The trend has started to appear in the medical literature. In July 2020, a team from the University of California San Francisco reported in the Journal of Emergency Medicine five cases of attempted suicide by sodium nitrite. The two cases who survived received methylene blue early in their clinical course.

That same month, a team from Portugal reported a similar, fatal case in the Journal of Forensic and Legal Medicine.

A team from the University of Illinois at Chicago responded to the UCSF team’s publication this past March with five cases of their own. Two of those patients also survived.

De Luca’s case turned out to be an accidental ingestion. “Secondary methemoglobinemia due to the adulteration of defrosted yellowfin tuna with sodium nitrite is strongly suspected,” De Luca told MedPage Today. “Indeed, about 10 cases of intoxication were reported from the North to South of Italy during the first week of June. No fatalities were reported.”

He said he’s a supporter of “free open access medical education” and strongly believes that sharing information “is a powerful way to improve our knowledge through discussion. I love how Twitter can be used as a case teaching tool even across continents.”