Last updated:
2/26/2026
Years published: 2026
NORD gratefully acknowledges Vikram Chinnaiyan, MD Candidate, University of South Florida Morsani College of Medicine, Katiana Garagozlo, MD, Assistant Professor, University of South Florida Morsani College of Medicine and Gioconda Alyea, MD (FMG), MS, National Organization for Rare Disorders for assistance in the preparation of this report.
Summary
Pulmonary interstitial glycogenosis (PIG) is a rare type of lung disease that affects children and especially infants.
PIG is characterized by respiratory issues, including difficulty with breathing, dry cough, and increased effort with breathing.2 It presents soon after birth, typically within 9 months of life.1 The signs and symptoms include bluish color of skin or lips (cyanosis), increased respiratory rate (tachypnea), and decreased oxygen in blood (hypoxemia).2 Due to these features of the condition, there is increased risk of poor growth, lung infections, and poor lung development. However, PIG typically resolves by end of infancy and has good long-term outcomes.3
PIG is considered a developmental disorder, meaning it happens while the lungs are still growing. In PIG, certain immature lung cells contain too much glycogen, which is a stored form of sugar, but the cause is not known.4 These cells line the tiny air sacs in the lungs (alveoli) that are responsible for gas (oxygen and carbon dioxide) exchange. When there are too many of these cells, oxygen and carbon dioxide do not move in and out of the lungs as well as they should.
There is no cure for PIG. Treatment is primarily supportive to manage symptoms while the lungs mature.5 Management often includes supplemental oxygen (oxygen tank or concentrator), with or without ventilatory support (use of a mechanical ventilator or continuous positive airway pressure [CPAP] machine or bilevel positive airway pressure [BiPAP] machine).6
Some doctors may prescribe steroid medications (glucocorticoids) to limit overgrowth of PIG cells following a careful assessment of potential benefits and risks by the doctors and the patients.⁶
In addition, infants should receive routine childhood vaccinations, avoid smoke and other environmental irritants, and maintain adequate nutrition to support growth and healing.
PIG is considered a type of interstitial lung disease (chILD).
Pulmonary interstitial glycogenosis (PIG) shares common symptoms with other diseases within childhood interstitial lung disease (chILD syndrome). The condition begins very early in life, often within the first few weeks after birth. In most cases, it improves on its own and resolves by the end of the first year of life, with good long-term outcomes.1,3,7 However, the respiratory symptoms may continue into adolescence.1 The signs and symptoms may include the following:2,7
Pulmonary interstitial glycogenosis (PIG) is classified as part of a group of lung conditions called childhood interstitial lung disease (child), a group of lung diseases in infants involving the cells within lungs that often cause similar breathing problems.4
The cause of PIG is not known.4 So far, no genes have been identified as causes of PIG.
Lung development in newborns (neonates) involves the creation of small sacs (alveoli) with thin membranes that enable oxygen and carbon dioxide exchange. PIG is a development disorder characterized by the persistence of immature cells called mesenchymal cells that contain too much glycogen, a form of stored sugar.4 Glycogen is a large macromolecule built from simple sugar units (glucose). The walls separating alveoli are made of mesenchymal cells. These cells have large amounts of glycogen during early lung development.8 Normally, they lose their glycogen as the lungs mature.
However, in babies with PIG, mesenchymal cells mature later than normal and continue to grow while containing large amounts of glycogen. This thickens the tissue between the air sacs and blood vessels, making gas exchange less efficient. As a result, infants develop low oxygen levels in the blood (hypoxemia) and tissues (hypoxia), leading to bluish skin discoloration, increased effort with breathing, and other respiratory symptoms.
PIG may be associated with other conditions, such as congenital heart disease (heart defects that are present at birth) and pulmonary hypertension (high blood pressure in lung arteries).8
Pulmonary interstitial glycogenosis (PIG) is a very rare condition. As per 2026, there are less than 100 cases documented in the medical literature.9
It is reported that the prevalence of childhood interstitial lung disease (chILD) is 1.3 to 3.6 children per million. Each year, about 0.1 to 16 children per 100,000 are newly diagnosed with some form of chILD.9 Since PIG is a subset of chILD, the incidence and prevalence of PIG are much lower than these reported numbers. The age of onset is in early infancy (less than 8 months) and it often presents in newborn babies shortly after birth.1
The diagnostic process for pulmonary interstitial glycogenosis (PIG) begins with an evaluation for childhood interstitial lung disease.
When infants and young children have widespread (diffuse) lung disease, meaning that many areas of the lungs are affected, clinicians use the term “chILD (childhood interstitial lung disease) syndrome” to identify those who require urgent diagnostic workup (testing) to determine the exact underlying chILD condition. chILD syndrome may be suspected in newborns with persistent breathing symptoms along with physical signs of breathing difficulty. However, other conditions that can cause similar symptoms must be ruled out first.
A diagnosis of chILD syndrome is made when an infant has at least three of the following four criteria, after common causes of diffuse lung disease have been excluded:2,5
PIG is one of several possible diagnoses that may be identified through the diagnostic workup triggered by chILD syndrome. Infants with PIG typically develop respiratory distress immediately after birth or within the first few months of life. The most common symptoms include increased respiratory effort when breathing and low blood oxygen levels (hypoxemia).3, 9
A high-resolution CT (computed tomography) scan of the chest is typically ordered to look for specific lung changes such as hazy or cloudy areas in the lungs (ground-glass opacities).2
However, these imaging findings can look similar to other lung conditions that affect newborns, particularly genetic disorders affecting surfactant (a substance that helps the lungs work properly). For this reason, imaging alone cannot confirm the diagnosis of PIG, but the findings are helpful in guiding the need for genetic testing and/or biopsy.
Several laboratory tests and procedures are commonly used to evaluate disease severity and support the diagnosis:2
The diagnosis of PIG can only be confirmed with a surgical lung biopsy. During this procedure, a small sample of lung tissue is removed and examined under a microscope. The tissue is treated with special stains that allow doctors to identify the characteristic cells seen in PIG.2,9 All lung biopsies showing PIG also demonstrate alveolar growth abnormalities with simplified alveolar development (reduced alveolarization).3, 9
During the diagnostic process, doctors will also look for other conditions that may occur alongside PIG. Many infants with PIG have other lung or heart problems.
There is currently no cure for pulmonary interstitial glycogenosis (PIG).5 Treatment focuses on supporting breathing, managing symptoms, and preventing complications while the lungs mature.
Most children with PIG have favorable outcomes, and many improve over time. However, in rare cases with severe lung damage, a lung transplant may be needed.6 Even when symptoms improve, some children may continue to have changes (abnormalities) on lung imaging tests or have reduced lung function (pulmonary function deficits) that can persist into adolescence.
Children with PIG should receive routine childhood vaccinations and avoid lung irritants, such as cigarette smoke, which can worsen breathing problems.6 Supplemental oxygen is often used to help improve low oxygen levels in the blood (hypoxemia). During periods of more serious breathing difficulty, breathing support (ventilatory support) may be also be needed.
There is no clear consensus on the use of glucocorticoids, medications commonly used to reduce inflammation. In theory, glucocorticoids may limit the growth of immature PIG cells.⁶ However, available evidence suggests they may be effective primarily in the diffuse form of PIG.⁶ The decision to use glucocorticoids is made on a case-by-case basis after carefully weighing potential risks and benefits.⁵
People affected with PIG should be cared for by a team of multiple specialists working together in a coordinated way to provide high-quality care. These specialists may include doctors who specialize in lung and breathing problems in children (pediatric pulmonologists), doctors who read imaging tests, such as chest X-rays and CT scans to look for changes in the lungs (radiologists), surgeons, doctors who examine tissue samples under a microscope to confirm a diagnosis (pathologists), and healthcare professionals who help manage breathing treatments, oxygen therapy, and ventilator support (respiratory therapists).5
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