Overview
Class I glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most severe form of G6PD deficiency, a genetic condition that affects red blood cells. G6PD is an enzyme that helps protect red blood cells from damage caused by certain chemicals and oxidative stress. While milder forms of G6PD deficiency (Classes II-V) only cause problems when triggered by specific foods, infections, or medications, Class I G6PD deficiency causes chronic nonspherocytic hemolytic anemia (CNSHA), meaning red blood cells are constantly being destroyed even without any triggers. This ongoing breakdown of red blood cells leads to persistent anemia that is present from birth or early infancy. People with Class I G6PD deficiency typically experience ongoing fatigue, pale skin, yellowing of the skin and eyes (jaundice), dark-colored urine, and an enlarged spleen. Newborns may develop severe jaundice shortly after birth, which can be dangerous if not treated promptly. Episodes of more severe anemia can be triggered by infections, certain medications (such as sulfa drugs, antimalarials, and aspirin), or eating fava beans, on top of the already existing baseline anemia. There is currently no cure for Class I G6PD deficiency. Treatment focuses on managing the chronic anemia and preventing hemolytic crises. This may include blood transfusions during severe episodes, folic acid supplementation to support red blood cell production, and strict avoidance of known triggers. In some cases, removal of the spleen (splenectomy) may be considered to reduce the rate of red blood cell destruction. Monitoring by a hematologist is essential for long-term management.
Key symptoms:
Chronic anemia (low red blood cell count that doesn't go away)Persistent fatigue and low energyPale skinYellowing of the skin and eyes (jaundice)Dark or tea-colored urineEnlarged spleenShortness of breath, especially with activityRapid heartbeatSevere newborn jaundiceEpisodes of worsened anemia during illness or after certain medicationsGallstonesDelayed growth in childrenDizziness or lightheadedness
X-linked recessive
Carried on the X chromosome; typically affects males more than females
Neonatal
Begins at or shortly after birth (first 4 weeks)
Treatments
No FDA-approved treatments are currently listed for Class I glucose-6-phosphate dehydrogenase deficiency.
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Specialists
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Treatment Centers
8 centersBaylor College of Medicine Rare Disease Center ↗
Baylor College of Medicine
📍 Houston, TX
🏥 NORDStanford Medicine Rare Disease Center ↗
Stanford Medicine
📍 Stanford, CA
🔬 UDNNIH Clinical Center Undiagnosed Diseases Program ↗
National Institutes of Health
📍 Bethesda, MD
🔬 UDNUCLA UDN Clinical Site ↗
UCLA Health
📍 Los Angeles, CA
🔬 UDNBaylor College of Medicine UDN Clinical Site ↗
Baylor College of Medicine
📍 Houston, TX
🔬 UDNHarvard/MGH UDN Clinical Site ↗
Massachusetts General Hospital
📍 Boston, MA
🏥 NORDMayo Clinic Center for Individualized Medicine ↗
Mayo Clinic
📍 Rochester, MN
👤 Mayo Clinic Center for Individualized Medicine
🏥 NORDUCLA Rare Disease Day Program ↗
UCLA Health
📍 Los Angeles, CA
Travel Grants
No travel grants are currently matched to Class I glucose-6-phosphate dehydrogenase deficiency.
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Caregiver Resources
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Social Security Disability
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Questions for your doctor
Bring these to your next appointment
- Q1.What specific G6PD mutation does my child have, and how severe is it expected to be?,Can you provide a complete list of medications and foods that must be avoided?,How often will blood tests and check-ups be needed?,At what hemoglobin level would a blood transfusion be recommended?,Should we consider splenectomy, and what are the risks and benefits?,Are there signs of iron overload we should watch for, and will chelation therapy be needed?,What should we do if our child develops a fever or infection — when should we go to the emergency room?
Common questions about Class I glucose-6-phosphate dehydrogenase deficiency
What is Class I glucose-6-phosphate dehydrogenase deficiency?
Class I glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most severe form of G6PD deficiency, a genetic condition that affects red blood cells. G6PD is an enzyme that helps protect red blood cells from damage caused by certain chemicals and oxidative stress. While milder forms of G6PD deficiency (Classes II-V) only cause problems when triggered by specific foods, infections, or medications, Class I G6PD deficiency causes chronic nonspherocytic hemolytic anemia (CNSHA), meaning red blood cells are constantly being destroyed even without any triggers. This ongoing breakdown of red bloo
How is Class I glucose-6-phosphate dehydrogenase deficiency inherited?
Class I glucose-6-phosphate dehydrogenase deficiency follows a x-linked recessive inheritance pattern. Genetic counseling can help families understand recurrence risk and testing options.
At what age does Class I glucose-6-phosphate dehydrogenase deficiency typically begin?
Typical onset of Class I glucose-6-phosphate dehydrogenase deficiency is neonatal. Age of onset can vary across affected individuals.