Greenish-blue discoloration of the brain and heart after treatment with methylene blue

Greenish-blue discoloration of the brain and heart was observed during the autopsy of a 63-year-old woman who had been treated with methylene blue for septic shock following a traffic accident. This "pistachio" or "avatar" discoloration occurs when the colorless metabolite leucomethylene blue is oxidized to methylene blue upon exposure to atmospheric oxygen. Other clinically documented adverse effects of methylene blue include greenish-blue urine and bluish discoloration of the skin and mucosa. In medicine, methylene blue is an inhibitor of nitric oxide synthase and guanylate cyclase with different clinical applications, namely, rapid reversal of circulatory shock that is refractory to fluid administration, inotropic agents, and vasoconstrictors. Postmortem differential diagnosis with putrefaction and hydrogen sulfide poisoning should be made, and forensic pathologists should be aware of methylene blue-related greenish-blue discoloration to avoid unnecessary workup and investigations.