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Congenital neutropenia (G6PC3)
People with this condition experience recurrent severe bacterial infections from infancy due to inadequate neutrophil production. Many affected individuals also have structural heart abnormalities and urogenital tract malformations. The condition results from pathogenic variants in G6PC3 and follows an autosomal recessive inheritance pattern.
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Overview
Congenital neutropenia (G6PC3) is characterised by severely reduced numbers of neutrophils in the blood from birth or early infancy. Neutrophils are white blood cells that form the body's first line of defence against bacterial and fungal infections. When neutrophil counts fall below critical thresholds, affected individuals become highly susceptible to life-threatening infections that can involve the skin, respiratory tract, digestive system, and bloodstream. This form of congenital neutropenia is distinguished from other inherited neutropenia syndromes by the frequent presence of additional features affecting the cardiovascular and urogenital systems.
The condition is rare, though exact prevalence figures are not well established. Cases have been reported worldwide across diverse ethnic backgrounds. Early recognition is crucial because prompt treatment with growth factors can substantially reduce infection risk and improve quality of life. Without appropriate management, severe bacterial infections in infancy and childhood can be fatal.
Symptoms & clinical features
The hallmark clinical feature is severe chronic neutropenia, typically identified in the first few months of life when infants present with recurrent bacterial infections. These infections commonly affect the skin (abscesses, cellulitis), mouth (severe gingivitis, oral ulcers), respiratory tract (pneumonia, sinusitis), and gastrointestinal system (perianal abscesses). Some affected children experience life-threatening sepsis or meningitis. The severity and frequency of infections generally correlate with how low the neutrophil count falls.
Beyond the immunological manifestations, many individuals display congenital heart defects, most commonly atrial septal defect or patent ductus arteriosus. Urogenital abnormalities are also frequent and may include undescended testes in males, kidney malformations, or structural anomalies of the urinary collecting system. Some affected individuals have prominent superficial veins visible on the trunk and limbs. Growth may be delayed in childhood, and mild facial dysmorphism has been noted in some cases, though these features are variable.
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Affected organs
The bone marrow is the primary site of dysfunction, where neutrophil precursor cells fail to mature properly, leading to severely reduced circulating neutrophil counts. This leaves the entire immune system compromised in its ability to mount effective responses to bacterial pathogens. The heart is frequently affected, with structural defects present from birth that may require surgical correction depending on severity. The urogenital system shows various developmental anomalies, ranging from mild to clinically significant malformations that may affect kidney function or require surgical intervention. The skin and mucous membranes become vulnerable sites for recurrent infection due to the neutropenia.
Risks & severity
Severity is variable but often substantial. Untreated severe chronic neutropenia carries a high risk of fatal bacterial infection during infancy and early childhood. The neutrophil count typically remains persistently low, often below 0.5 × 10⁹/L, which represents severe neutropenia. Congenital heart defects, when present, range from minor lesions requiring only monitoring to more significant defects necessitating surgical repair in infancy or early childhood.
With appropriate treatment using granulocyte colony-stimulating factor, most affected individuals can maintain neutrophil counts sufficient to prevent severe infections, substantially improving life expectancy and quality of life. However, some individuals require high doses of growth factor, and response can vary. Long-term surveillance is necessary because there may be a slightly increased risk of developing myelodysplastic syndrome or acute myeloid leukaemia, though this remains uncommon. Cardiac and urogenital anomalies require individual assessment and management according to their severity.
Genetic causes
Pathogenic variants in G6PC3 cause this condition. The G6PC3 gene provides instructions for producing glucose-6-phosphatase catalytic subunit 3, an enzyme that functions within the endoplasmic reticulum of cells. This enzyme catalyses the final step in both gluconeogenesis and glycogenolysis pathways, converting glucose-6-phosphate to glucose. Research suggests this process is particularly critical in neutrophil precursor cells for maintaining energy metabolism and managing cellular stress responses during maturation.
When G6PC3 carries pathogenic variants, the resulting enzyme has reduced or absent catalytic activity. This disrupts normal metabolic processes within developing neutrophils, leading to increased cellular stress and premature cell death before neutrophils can fully mature and enter the bloodstream. The mechanism by which G6PC3 dysfunction causes cardiac and urogenital developmental anomalies is not fully understood, but evidence suggests the enzyme plays important roles in cellular processes during embryonic organ development beyond its metabolic functions.
- G6PC3 glucose-6-phosphatase catalytic subunit 3
Inheritance pattern
Congenital neutropenia (G6PC3) follows an autosomal recessive inheritance pattern. This means an affected individual must inherit two pathogenic variants in G6PC3, one from each parent. Parents who each carry one pathogenic variant (carriers) typically have normal neutrophil counts and no symptoms because one working copy of the gene is sufficient for normal function.
When both parents are carriers, each pregnancy has a 25% chance of producing an affected child, a 50% chance of producing a carrier child, and a 25% chance of producing a child with two working gene copies. Siblings of an affected individual have a two-in-three chance of being carriers if they are unaffected. Genetic counselling can help families understand these risks and discuss reproductive options, including carrier testing for at-risk relatives.
When both parents are carriers, each child has a 25% chance of being affected, 50% of being a carrier, and 25% of being unaffected.
Diagnosis & testing
Diagnosis is typically suspected when an infant presents with severe chronic neutropenia and recurrent bacterial infections, particularly when accompanied by congenital heart or urogenital abnormalities. Initial blood tests reveal persistently low absolute neutrophil counts, often severely depressed. Bone marrow examination may show reduced numbers of mature neutrophils with evidence of maturation arrest at the promyelocyte or myelocyte stage.
Confirmation requires genetic testing to identify biallelic pathogenic variants in G6PC3. Testing is usually arranged through clinical genetics services via NHS Genomic Medicine Service pathways. The condition may be included in gene panel testing for congenital neutropenia disorders. Echocardiography and renal ultrasound are typically performed to assess for associated cardiac and urogenital malformations. Family history suggestive of consanguinity or previous affected siblings supports the diagnosis.
Management & lifestyle
Management centres on preventing infections and addressing associated complications. Granulocyte colony-stimulating factor is the mainstay of treatment, administered by subcutaneous injection to stimulate neutrophil production and maintain counts at safer levels. Dosing is individualised based on response, and regular blood monitoring tracks neutrophil counts and adjusts treatment accordingly. Most affected individuals show good response to growth factor therapy, substantially reducing infection frequency and severity.
Prompt treatment of any bacterial infection with appropriate antibiotics is essential. Some individuals may benefit from antibiotic prophylaxis, though this requires specialist assessment balancing infection risk against antibiotic resistance concerns. Congenital heart defects require cardiology assessment, with surgical correction performed when clinically indicated. Urogenital anomalies are managed by paediatric urology or nephrology specialists as appropriate. Long-term haematology follow-up monitors for potential development of myelodysplastic changes. Genetic counselling should be offered to families to discuss inheritance, recurrence risks, and reproductive options.
UK care pathway
Diagnosis and management of congenital neutropenia (G6PC3) occur through the NHS Genomic Medicine Service. Infants presenting with severe neutropenia and recurrent infections are typically referred to paediatric haematology, where clinical assessment may prompt referral to clinical genetics services for genetic testing. Gene panel testing for congenital neutropenia disorders would include G6PC3 analysis. Confirmed diagnoses trigger specialist haematology care with access to granulocyte colony-stimulating factor therapy and infection monitoring protocols.
Families receive support from specialist nurses and genetic counsellors who can explain the inheritance pattern, discuss implications for other family members, and provide information about carrier testing. Multidisciplinary care coordinates haematology, cardiology, and urology input as needed. NHS England's specialised commissioning frameworks support access to growth factor therapy and long-term monitoring.
Frequently asked questions
Will my child with G6PC3-related neutropenia be able to fight off common childhood infections?
With granulocyte colony-stimulating factor treatment to raise neutrophil counts, most children can manage common viral infections normally. Bacterial infections remain the main concern, but maintaining adequate neutrophil levels through growth factor therapy substantially reduces this risk. Close monitoring and prompt antibiotic treatment when infections occur are important safeguards.
Do all children with this condition need heart surgery?
Not all affected children have heart defects, and among those who do, severity varies considerably. Some defects are minor and require only monitoring, whilst others may need surgical repair. A paediatric cardiologist will assess your child individually and recommend treatment based on the specific cardiac findings.
If I have another child, what is the chance they will be affected?
If both you and your partner carry one pathogenic G6PC3 variant, each pregnancy has a 25% (one in four) chance of producing an affected child. Genetic counselling can discuss your family's specific situation, and options such as prenatal testing or preimplantation genetic testing may be available.
Will the neutropenia improve as my child gets older?
G6PC3-related neutropenia is typically a lifelong condition that does not spontaneously resolve with age. However, ongoing treatment with granulocyte colony-stimulating factor can maintain neutrophil counts at safer levels throughout life, and many individuals lead active lives with appropriate medical support and infection prevention strategies.