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Alveolar capillary dysplasia
ACD is a severe condition that prevents proper oxygen exchange in the lungs, typically presenting shortly after birth. It is often life-threatening for affected infants due to respiratory failure.
Overview
Alveolar capillary dysplasia (ACD), sometimes referred to as alveolar capillary dysplasia with misalignment of pulmonary veins (ACD/MPV), is a very rare genetic disorder that profoundly affects the development of the lungs. Specifically, it impacts the tiny air sacs (alveoli) where oxygen and carbon dioxide are exchanged, and the surrounding blood vessels (capillaries) [PMID:34421111]. In individuals with ACD, these crucial structures are not formed correctly or are not present in sufficient numbers. This malformation means that oxygen cannot efficiently pass from the air into the bloodstream, and carbon dioxide cannot be effectively removed.
ACD typically presents in newborns, often within hours or days of birth, with severe respiratory distress. The condition is associated with a high mortality rate due to the lung's inability to perform its essential function of gas exchange. It is a complex condition that requires specialist medical attention from birth.
Symptoms & clinical features
Newborns with alveolar capillary dysplasia usually exhibit severe respiratory distress very soon after birth. This is the primary symptom and is often characterised by rapid breathing (tachypnoea), difficulty breathing (dyspnoea), and a bluish discolouration of the skin and mucous membranes (cyanosis), indicating insufficient oxygen levels in the blood [PMID:24176466].
Infants with ACD typically require ventilatory support immediately. Despite this, their oxygen levels often remain low, and they may experience high blood pressure in the arteries leading to the lungs (pulmonary hypertension). Other signs may include an enlarged heart (cardiomegaly) due to the strain on the cardiovascular system. Due to the rapid and severe onset of breathing problems, ACD is usually identified in the neonatal intensive care unit (NICU).
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Affected organs
The primary organ affected by alveolar capillary dysplasia is the lungs [PMID:24176466]. The condition directly impacts the development of the alveoli, which are the small air sacs responsible for gas exchange, and the capillaries that surround them. The problem lies with the failure of these capillaries to form alongside the alveoli, or their misalignment, meaning they are not positioned correctly to facilitate oxygen uptake.
Secondary effects can be seen in the heart, which may become enlarged due to the increased workload caused by pulmonary hypertension. Other organs may also be affected if development is part of a broader syndrome, although severe respiratory failure usually dominates the clinical picture.
Risks & severity
Alveolar capillary dysplasia is a severe condition, often considered life-threatening. The prognosis for infants diagnosed with ACD is generally poor, with many not surviving beyond the neonatal period despite intensive medical interventions [PMID:34421111]. The severity of respiratory failure from birth usually dictates the clinical course.
No specific lifetime risks can be discussed as survival into adulthood is extremely rare. Similarly, there is no typical age of onset other than birth or within the first few days of life, as the condition manifests with congenital lung abnormalities.
Genetic causes
Alveolar capillary dysplasia is primarily associated with pathogenic changes in the FOXF1 gene, which stands for Forkhead Box F1 [PMID:24176466]. The FOXF1 gene provides instructions for making a protein that plays a critical role during embryonic development, particularly in the formation of the lungs and the gastrointestinal tract. This protein acts as a transcription factor, meaning it helps control the activity of other genes.
In individuals with ACD, variants in the FOXF1 gene can disrupt its normal function. This disruption can lead to the improper development of the alveoli and capillaries in the lungs. While FOXF1 is the main gene linked to ACD, in some rare cases, the genetic cause might not be identified, suggesting that other genes or factors could also contribute to the condition.
- FOXF1 forkhead box F1
Inheritance pattern
Alveolar capillary dysplasia typically follows an autosomal dominant inheritance pattern. This means that a person only needs to inherit one copy of an altered FOXF1 gene from one parent to develop the condition.
In most cases of ACD, the genetic change is a 'de novo' mutation, meaning it occurs spontaneously in the affected individual and is not inherited from either parent. However, in some instances, a parent who shows no symptoms might carry the genetic change in some of their cells (germline mosaicism), which could be passed on. Genetic counselling is recommended for affected families to understand the inheritance patterns and potential risks for future pregnancies.
Each child has a 50% chance of inheriting the pathogenic variant, regardless of sex.
Diagnosis & testing
The diagnosis of alveolar capillary dysplasia is usually suspected in newborns presenting with severe, unexplained respiratory distress that does not respond to standard treatments for common neonatal lung conditions. Imaging techniques, such as a chest X-ray or CT scan, may show abnormal lung patterns. However, a definitive diagnosis often requires a lung biopsy, which allows for microscopic examination of lung tissue to identify the characteristic abnormalities of ACD [PMID:24176466].
Genetic testing for variants in the FOXF1 gene is crucial for confirming the diagnosis. This can be performed on a blood sample. In the UK, genetic testing for ACD would typically be initiated via a referral to a clinical genetics service, often following a consultation with a paediatric respiratory specialist or neonatologist. Relevant NHS R-codes for genetic testing may include R130 Hereditary pulmonary hypertension and related disorders, or R107 Generalised dysplasias, depending on the specific clinical presentation and how the test is requested through the NHS Genomic Medicine Service.
Management & lifestyle
Managing alveolar capillary dysplasia primarily focuses on providing intensive supportive care for respiratory failure, usually in a neonatal intensive care unit (NICU). This includes mechanical ventilation to assist breathing and medications to manage pulmonary hypertension, which is often a significant complication [PMID:24176466]. Despite intensive care, survival rates are very low due to the severe underlying lung malformation.
Because ACD is a rare and complex condition, care is typically provided by a multidisciplinary team of specialists, including neonatologists, paediatric respiratory consultants, and geneticists. Genetic counselling is an important part of the management pathway, offering information and support to families regarding the genetic cause, inheritance patterns, and reproductive options. There are currently no cures for ACD, and management addresses the symptoms rather than the underlying developmental defect.
UK care pathway
In the UK, suspected cases of alveolar capillary dysplasia would be managed within the NHS, often beginning in a neonatal intensive care unit. A referral to a clinical genetics service is a key step, facilitated by neonatologists or paediatric specialists. This referral enables access to genetic counselling and diagnostic genetic testing, which is delivered through the NHS Genomic Medicine Service (GMS). The GMS utilises a national testing directory, with specific R-codes (e.g., R130, R107) guiding appropriate genetic investigations. Genetic counsellors provide essential support, explaining the condition, inheritance, and implications for families.
Frequently asked questions
What is the life expectancy for a baby with alveolar capillary dysplasia?
Sadly, alveolar capillary dysplasia is a very severe condition. Most affected infants do not survive beyond the neonatal period, even with intensive medical support, due to the critical failure of lung function.
Is alveolar capillary dysplasia inherited from parents?
Although ACD is a genetic condition, it is often caused by a new (de novo) genetic change not inherited from either parent. However, in some rare cases, one parent might carry the genetic change without symptoms, so genetic counselling is important.
Can alveolar capillary dysplasia be detected during pregnancy?
Detecting ACD during pregnancy is challenging. While some severe lung abnormalities might be observed on ultrasound, these are generally non-specific. A definitive diagnosis typically requires examination of lung tissue after birth, or genetic testing where there is a very high suspicion.
What kind of doctors treat alveolar capillary dysplasia?
Newborns with ACD are typically cared for by a team of specialist doctors in a neonatal intensive care unit. This usually includes neonatologists, paediatric respiratory specialists, and clinical geneticists, supported by genetic counsellors and other healthcare professionals.
Are there any treatments for alveolar capillary dysplasia?
There is currently no cure for alveolar capillary dysplasia. Treatment focuses on supportive care, such as mechanical ventilation to help with breathing and medications to manage high blood pressure in the lungs, aiming to improve oxygen levels for the baby.
References
- Mandell E, Kinsella JP, Abman SH. Persistent pulmonary hypertension of the newborn. Pediatric pulmonology. 2021. PMID: 32930508
- Bishop NB, Stankiewicz P, Steinhorn RH. Alveolar capillary dysplasia. American journal of respiratory and critical care medicine. 2011. PMID: 21471096
- Mukherjee D, Konduri GG. Pediatric Pulmonary Hypertension: Definitions, Mechanisms, Diagnosis, and Treatment. Comprehensive physiology. 2021. PMID: 34190343
- Wang G, Wen B, Guo M. Identification of endothelial and mesenchymal FOXF1 enhancers involved in alveolar capillary dysplasia. Nature communications. 2024. PMID: 38898031
- Cornfield DN, Nogee LM. Rare to "Ubiquitinous": Alveolar Capillary Dysplasia, FOXF1, and a Sly Approach to Angiogenesis. American journal of respiratory and critical care medicine. 2023. PMID: 36608259
- deMello DE. Pulmonary pathology. Seminars in neonatology : SN. 2004. PMID: 15251148
- Bush A, Gilbert C, Gregory J. Interstitial lung disease in infancy. Early human development. 2020. PMID: 32958330
- Shirazi SP, Negretti NM, Jetter CS. Bronchopulmonary dysplasia with pulmonary hypertension associates with semaphorin signaling loss and functionally decreased FOXF1 expression. Nature communications. 2025. PMID: 40442177