Hello, Thank you for asking at HCM. If your sister has frequent pneumonia infections there are several causes that come to mind depending on her age also. In very young children the first things to think are foreign body or cystyc fibrosis. In adults and old patients chronic bronkitis might be a cause due to getting acute time after time. Something good to consider is having a CBC, ERS done and also a chest xray, lung CT scan or MRI. Some rare causes of recurrent lung infection are yeast infection or tuberculosis but specific tests like PPD skin test also. What can seem like penumonia but is not infection is sarcoidosis and is a common cause of lung disease in women and specific tests should be done to rule it out. Hope this answers to your question and is helpful to you.