A 62-year-old man was diagnosed with Type 1 cytochrome B5 reductase deficiency, a rare genetic blood disorder that usually appears in childhood, after presenting with blue-tinged skin and low oxygen levels. According to Gram Research analysis, his blood contained 17% methemoglobin—a non-functional form of hemoglobin—which was confirmed by genetic testing showing two faulty copies of the CYB5R3 gene. This case demonstrates that doctors should test for this rare condition even in older adults when pulse oximetry readings don’t match actual oxygen levels.
A 62-year-old man came to the hospital with blue-tinged skin and trouble breathing, which led doctors to discover he had a rare genetic blood disorder called Type 1 cytochrome B5 reductase deficiency. This condition causes a buildup of a form of hemoglobin that can’t carry oxygen properly. According to Gram Research analysis, this case is important because the disease is usually found in children, but this patient wasn’t diagnosed until he was elderly. The man’s blood appeared chocolate-brown instead of red, and his oxygen levels were dangerously low. Doctors treated him with vitamin C and extra oxygen, and the case reminds medical professionals to check for this rare condition even in older patients.
Key Statistics
A 2026 case report published in the Irish Journal of Medical Science documented a 62-year-old male patient with Type 1 cytochrome B5 reductase deficiency who had a methemoglobin level of 17%, demonstrating that this rare genetic blood disorder can remain undiagnosed into late adulthood.
In the reported case, the patient’s pulse oximetry readings were misleadingly high despite actual arterial blood oxygen saturation being significantly lower, highlighting how standard oxygen measurement devices can fail to detect methemoglobinemia.
Genetic testing revealed the 62-year-old patient carried two homozygous pathogenic mutations in the CYB5R3 gene, confirming the autosomal recessive inheritance pattern of Type 1 cytochrome B5 reductase deficiency.
The Quick Take
- What they studied: A single case of a rare genetic blood disorder that wasn’t diagnosed until the patient was 62 years old, even though it usually shows up in childhood
- Who participated: One 62-year-old male patient who came to the hospital with blue-tinged skin and difficulty breathing
- Key finding: The patient had a methemoglobin level of 17%, which means 17% of his blood couldn’t carry oxygen properly. His blood was chocolate-brown colored instead of normal red, and pulse oximetry machines gave misleadingly high oxygen readings
- What it means for you: If you or someone you know has unexplained blue-tinged skin and low oxygen levels that don’t match what a pulse oximeter shows, doctors should test for this rare condition. Even older adults can have it, so age shouldn’t rule it out
The Research Details
This is a case report, which means doctors documented the medical story of one patient with an unusual diagnosis. The 62-year-old man came to the hospital complaining of cyanosis (blue-tinged skin) and shortness of breath. Doctors performed several tests including arterial blood gas analysis, which measures oxygen and other gases directly from the blood. They also did genetic testing to identify mutations in the CYB5R3 gene.
The doctors discovered that his blood had an unusual chocolate-brown appearance instead of the normal bright red color. This color change happens because of a buildup of methemoglobin, a form of hemoglobin that can’t carry oxygen. The genetic test confirmed he had two copies of a faulty CYB5R3 gene, meaning he inherited the condition from both parents.
This type of case report is valuable because it documents an unusual presentation of a known genetic disease in an unexpected age group, helping doctors recognize similar cases in the future.
Case reports like this one are important because they alert doctors to possibilities they might not normally consider. Type 1 cytochrome B5 reductase deficiency is so rare and usually diagnosed in children that doctors might not think to test for it in an older adult. By documenting this case, the medical team helps other doctors recognize the disease in elderly patients who might otherwise be misdiagnosed or treated incorrectly.
This is a single case report, which is the lowest level of scientific evidence. However, it’s valuable for documenting unusual medical presentations. The diagnosis was confirmed with genetic testing, which is the gold standard for identifying genetic disorders. The key limitation is that one case cannot prove how common this condition is in older adults or how treatment outcomes might differ from childhood cases.
What the Results Show
The patient presented with cyanosis (blue-tinged skin) and shortness of breath, which are classic signs of low oxygen in the blood. When doctors tested his arterial blood, they found it had a distinctive chocolate-brown color instead of normal red blood. Laboratory tests showed his methemoglobin level was 17%, meaning about one-sixth of his hemoglobin couldn’t carry oxygen.
One important finding was that the patient’s pulse oximeter (the device that clips on your finger) showed oxygen saturation readings that were misleadingly high. This happened because the machine couldn’t distinguish between normal hemoglobin and the non-functional methemoglobin. This mismatch between what the pulse oximeter showed and what the arterial blood gas test revealed was a crucial clue to the diagnosis.
Genetic testing confirmed the patient had two copies of a pathogenic (disease-causing) mutation in the CYB5R3 gene. This means he inherited the faulty gene from both parents, which is why he developed the disease. The patient was started on vitamin C supplementation and supplemental oxygen therapy, which are standard treatments for this condition.
The case highlights that hypoxemia (low blood oxygen) can exist even when pulse oximetry readings appear normal or acceptable. This discrepancy between different measurement methods was actually the key to making the diagnosis. The patient’s presentation with cyanosis in adulthood, rather than childhood, suggests that some people with this genetic condition may have milder symptoms that go unnoticed for decades.
Type 1 cytochrome B5 reductase deficiency is well-documented in medical literature, but almost all reported cases involve children or young adults. This case is unusual because the patient wasn’t diagnosed until age 62. Previous research shows this condition is inherited in an autosomal recessive pattern, meaning you need two faulty copies of the gene to develop the disease. This case confirms that pattern but extends our understanding by showing the disease can remain undiagnosed into late adulthood.
This is a single case report, so we cannot draw broad conclusions about how common late-onset diagnosis is or whether treatment outcomes differ in older adults. The report doesn’t provide long-term follow-up data on how well the patient responded to vitamin C and oxygen therapy. We don’t know if there are other older adults with this condition who haven’t been diagnosed yet. Additionally, the case doesn’t explain why this particular patient’s symptoms didn’t appear until age 62, when the genetic mutation was present from birth.
The Bottom Line
If you have unexplained blue-tinged skin (cyanosis) and low blood oxygen levels that don’t match pulse oximeter readings, ask your doctor to perform an arterial blood gas test to check for methemoglobin. This is especially important if you have a family history of blood disorders. Treatment typically involves vitamin C supplementation and supplemental oxygen. These recommendations are based on a single case report, so discuss your specific situation with your healthcare provider.
This case is most relevant to doctors and healthcare providers who care for patients with unexplained cyanosis or oxygen problems. It’s also important for people with a family history of this genetic disorder or similar blood conditions. Anyone experiencing persistent blue-tinged skin should see a doctor, as this can indicate various serious conditions. Genetic counselors should be aware of this case when advising families with known CYB5R3 mutations.
If someone has this condition and starts treatment with vitamin C and oxygen therapy, improvements in oxygen levels and reduction in cyanosis can occur relatively quickly, though this case report doesn’t specify exact timelines. Long-term management requires ongoing monitoring and continued supplementation.
Frequently Asked Questions
What is methemoglobinemia and why does it cause blue skin?
Methemoglobinemia occurs when hemoglobin (the protein that carries oxygen in blood) becomes oxidized and can’t carry oxygen properly. This causes oxygen-deprived blood to appear darker, which shows through the skin as a blue or purple tint called cyanosis.
Can you get this rare blood disorder later in life if you’re born with it?
Type 1 cytochrome B5 reductase deficiency is present from birth because it’s genetic, but symptoms may not appear or be noticed until adulthood. This 62-year-old case shows the condition can remain undiagnosed for decades before causing noticeable symptoms like cyanosis and shortness of breath.
Why did the pulse oximeter give wrong readings in this patient?
Pulse oximeters measure light absorption to estimate oxygen levels, but they cannot distinguish between normal hemoglobin and methemoglobin. Both absorb light similarly, so the device showed falsely high oxygen readings despite the patient actually having low functional oxygen-carrying capacity.
How is Type 1 cytochrome B5 reductase deficiency treated?
Treatment typically includes vitamin C supplementation and supplemental oxygen therapy. Vitamin C helps reduce methemoglobin back to functional hemoglobin. This 62-year-old patient was managed with these approaches, though long-term outcomes weren’t detailed in the case report.
Should doctors test older adults for this condition?
Yes, according to this case report, doctors should consider methemoglobinemia in older patients presenting with unexplained cyanosis and low oxygen levels, especially when pulse oximetry readings don’t match arterial blood gas results. Age alone shouldn’t rule out testing for this rare genetic disorder.
Want to Apply This Research?
- Track oxygen saturation readings from both pulse oximetry and arterial blood gas tests if you have this condition, noting any discrepancies between the two measurements. Record skin color changes (presence or absence of blue tint) daily and vitamin C supplementation doses.
- If diagnosed with this condition, users should set daily reminders for vitamin C supplementation and oxygen therapy as prescribed. Log any symptoms like shortness of breath or increased blue-tinged skin to share with healthcare providers during follow-up appointments.
- Maintain a symptom diary tracking cyanosis severity, oxygen levels, and energy levels. Schedule regular blood tests to monitor methemoglobin levels and ensure treatment effectiveness. Document any changes in symptoms or oxygen requirements to discuss with your medical team.
This article describes a single case report of a rare genetic blood disorder and should not be used for self-diagnosis. If you experience unexplained blue-tinged skin, shortness of breath, or oxygen saturation problems, consult a qualified healthcare provider immediately. Genetic testing and specialized blood tests are required for accurate diagnosis. This information is for educational purposes only and does not replace professional medical advice, diagnosis, or treatment. Always seek the guidance of your physician or other qualified healthcare provider with any questions you may have regarding a medical condition.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.