Pulmonary Interstitial Glycogenesis
Pulmonary Interstitial Glycogenosis (PIG) is caused by an abnormal accumulation of glycogen in specific cells of the lung. These cells are located in the interstitium, the space between the air sacs in the lungs. The excess glycogen leads a thickening of the space, making it difficult for oxygen to get from the air sacs into the bloodstream.
The cause of PIG remains unclear. The accumulation of glycogen has also been seen in other lung conditions to different degrees, especially those associated with poor lung growth. Based on these observations and the lack of inflammation in the lungs, it is thought that PIG is a result of abnormal development of the lungs in the fetus and young infant. However, a report of PIG in a pair of identical twins also point to the likely genetic predisposition for this disorder. Further studies are needed to accurately define this lung disorder.
- Lab work to rule out other causes of these symptoms, such as cystic fibrosis or immunodeficiency, is often performed.
- A high-resolution computed tomography (CT) scan of the lungs may show findings consistent with an interstitial lung disease.
- However, the imaging appearance of PIG is highly variable and non-specific for PIG. With the few case reports of PIG, it is currently difficult to make the diagnosis solely based on radiographic imaging.
- A bronchoscopy with bronchoalveolar lavage (BAL) may be performed which can look for infection, inflammation and signs of aspiration into the lungs. Currently, a definitive diagnosis of PIG can only be made through lung biopsy. The biopsy tissue typically shows little inflammation. The hallmark of PIG is the accumulation of glycogen in the lung interstitial cells.
Information supplied with thanks to chILD Foundation US.