A patient developed unusual dark patches on their face and inside their mouth that looked like a serious condition called Addison’s disease. However, doctors discovered the real cause was vitamin B12 deficiency—a condition many people don’t realize can affect skin color. This case is important because it shows how vitamin B12 deficiency can hide behind unusual symptoms that doctors might mistake for other diseases. The story reminds doctors to think about less common ways that familiar health problems can show up in patients.

The Quick Take

  • What they studied: A single patient who developed dark patches on their face and inside their mouth, and doctors worked to figure out what was causing it
  • Who participated: One patient with vitamin B12 deficiency who developed unusual dark skin patches on the face and mouth
  • Key finding: Dark patches on the face and mouth turned out to be caused by vitamin B12 deficiency, not the more serious condition doctors initially suspected
  • What it means for you: If you have unexplained dark patches on your skin, especially on your face or mouth, ask your doctor to check your vitamin B12 levels. This is a rare symptom, but it’s worth investigating because B12 deficiency is treatable

The Research Details

This is a case report, which means doctors documented one specific patient’s experience in detail. The patient came to the hospital with dark patches covering their face and the inside of their mouth. The doctors examined the patient carefully and ran blood tests to figure out what was causing these dark spots. They also reviewed medical literature—basically all the published research they could find—about similar cases to understand how vitamin B12 deficiency can show up as skin color changes.

The doctors suspected the patient might have Addison’s disease, which is a serious condition that also causes dark patches on skin. However, when they tested the patient’s blood, they found that the real problem was vitamin B12 deficiency. This discovery was surprising because dark patches from B12 deficiency are usually seen on hands and feet, not on the face and mouth.

This case matters because it teaches doctors an important lesson: sometimes common diseases like vitamin B12 deficiency can show up in unusual ways that look like rare, serious diseases. By documenting this case and reviewing similar cases in medical literature, doctors can learn to recognize these uncommon presentations. This helps them diagnose and treat patients faster and more accurately.

This is a case report based on one patient, which is the lowest level of scientific evidence. It’s useful for teaching doctors about unusual presentations of known diseases, but it cannot prove that B12 deficiency always causes facial dark patches. The value of this report comes from the detailed documentation and the review of existing medical literature that supports the findings. Readers should understand this describes a rare situation, not a common occurrence.

What the Results Show

The patient presented with dark patches (hyperpigmentation) covering the face and the inside of the mouth. These dark patches looked very similar to what doctors see in Addison’s disease, which is a serious hormonal condition. The patient’s skin appeared darker in these areas, which was the main symptom that brought them to medical attention.

When doctors performed blood tests, they discovered the patient had vitamin B12 deficiency. This was the actual cause of the dark patches. After the diagnosis was confirmed, the patient likely received B12 treatment, which would address the underlying deficiency.

The case is particularly interesting because vitamin B12 deficiency typically causes dark patches on the hands and feet, not on the face and mouth. This unusual presentation made the diagnosis tricky at first, which is why doctors initially thought about other diseases.

The case review of medical literature revealed that while skin color changes from B12 deficiency are known, facial and oral cavity involvement is extremely rare. Most documented cases show dark patches in other locations. This rarity makes the case noteworthy and worth sharing with other doctors so they can recognize this possibility in their own patients.

Vitamin B12 deficiency is well-known to cause various skin problems, including dark patches. However, most previous cases in medical literature describe these patches appearing on hands and feet. This case adds to medical knowledge by documenting a rare presentation on the face and mouth. It confirms that while uncommon, this presentation is possible and should be considered in the diagnostic process.

This is a single case report, so it describes only one patient’s experience. We cannot conclude that all people with facial dark patches have B12 deficiency, or that all people with B12 deficiency will develop facial dark patches. The case is valuable for teaching doctors to think about this possibility, but larger studies would be needed to understand how often this occurs. Additionally, the report doesn’t provide detailed information about the patient’s treatment response or long-term follow-up.

The Bottom Line

If you develop unexplained dark patches on your skin, especially on your face or mouth, consult a healthcare provider. Ask them to check your vitamin B12 levels as part of the evaluation. If B12 deficiency is found, it can be treated with supplements or injections. This recommendation has moderate confidence because while facial dark patches from B12 deficiency are rare, they are treatable when identified.

This case is most relevant for doctors and healthcare providers who need to recognize unusual presentations of common diseases. For patients, this is relevant if you have unexplained dark skin patches and haven’t found a diagnosis yet. People at higher risk for B12 deficiency—including vegetarians, vegans, older adults, and people with certain digestive conditions—should be especially aware. This case is less relevant for people without skin changes or those already diagnosed with other conditions causing dark patches.

If dark patches are caused by B12 deficiency, treatment with B12 supplements or injections typically begins working within weeks to months. However, skin color changes may take longer to fade—sometimes several months—after the deficiency is corrected. The timeline depends on how severe the deficiency was and how long it lasted.

Want to Apply This Research?

  • If you’re being treated for B12 deficiency with facial dark patches, take photos of the affected areas monthly and track them in your app. Note the date, location, and appearance. Also log your B12 supplement doses and any changes in energy levels or other symptoms. This creates a visual record of improvement over time.
  • Set reminders to take B12 supplements as prescribed. If you’re at risk for B12 deficiency (vegetarian, vegan, or have digestive issues), use the app to track foods rich in B12 or schedule regular B12 injections. Log any new skin changes or symptoms to discuss with your doctor.
  • Create a long-term tracking system that includes monthly photos of skin areas, B12 supplement adherence, energy levels, and any neurological symptoms (like tingling or numbness). Share this data with your healthcare provider at regular check-ups to monitor treatment effectiveness and adjust dosing if needed.

This case report describes a rare presentation of vitamin B12 deficiency and is intended for educational purposes. It should not be used for self-diagnosis. If you experience unexplained dark patches on your skin or suspect you have a vitamin B12 deficiency, consult a qualified healthcare provider for proper evaluation and diagnosis. This article does not replace professional medical advice, and individual cases may vary significantly. Always seek medical attention for persistent or concerning skin changes.