Sulfhemoglobinemia

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Sulfhemoglobinemia

What it is
Sulfhemoglobinemia is a rare condition where an abnormal form of hemoglobin called sulfhemoglobin builds up in red blood cells. Sulfhemoglobin is greenish and cannot be converted back to normal hemoglobin, so it lowers the blood’s ability to carry oxygen. This can cause a blue‑green tint to the skin, lips, and nails (cyanosis), even if a blood test looks largely normal.

What causes it
- Sulfur-containing drugs (examples include certain antibiotics and pain relievers: sulfonamides such as sulfamethoxazole, phenacetin, metoclopramide, dapsone, phenazopyridine, trimethoprim-sulfamethoxazole)
- Gut bacteria that produce hydrogen sulfide (for example Morganella morganii)
- Other sulfur exposures

Symptoms
- Cyanosis (blue‑green tint of skin, lips, and nails)
- In many cases, there may be few or no other obvious symptoms

How long it lasts
- Sulfhemoglobin persists for the life of the affected red blood cells, about 100–120 days. It often resolves as new red blood cells replace old ones.

Treatment
- Stop the offending drug or exposure
- In severe cases, a blood transfusion may be needed

Complications and risks
- Low oxygen in tissues (hypoxemia)
- Methemoglobinemia can occur in some cases

Risk factors
- Pulmonary arteriovenous malformation can increase risk

Prevention
- Avoid sulfur-containing drugs when alternatives are available
- If a sulfur-containing medicine is necessary, close medical monitoring is advised

Summary
Sulfhemoglobinemia is a rare, drug- or exposure‑related condition that changes hemoglobin to a form that cannot carry oxygen. It causes notable cyanosis and may require stopping the source and, in severe cases, a transfusion. It typically improves as the body replaces the affected red blood cells.