Many rare diseases involve the lungs and respiratory system. They can be limited to the lung itself (eg, idiopathic alveolar proteinosis) or be part of a systemic disease that causes additional symptoms (eg, Wegener’s disease). Within diseases of the lung, conditions may primarily affect certain structures, such as the alveoli, small airways, trachea, or blood vessels.
Some rare lung diseases are autoimmune in nature (eg, anti-glomerular basement membrane disease) or are a form of vasculitis (eg, Takayasu’s arteritis). Others, like cystic fibrosis (CF), are inherited, while many others are not. Environmental triggers may be responsible for some, and in many more cases, the true cause remains obscure.
Although most rare lung diseases are unfamiliar to a majority of people, some have received wider attention, including CF, pulmonary arterial hypertension (PAH), idiopathic pulmonary fibrosis (IPF), and hereditary angioedema (HAE).
Sometimes a rare respiratory disease is diagnosed relatively quickly; a thorough medical exam and history can help reveal clues. However, because a family history is not always a key element, the correct diagnosis can sometimes take a while.
For some rare respiratory diseases, like CF, symptoms begin early in life; in others, symptoms ranging in intensity from mild to severe begin in later childhood or adulthood and onset may be sudden or gradual.
Potential symptoms are diverse and may include chronic cough, susceptibility to infection, shortness of breath, fatigue, chest pain, or respiratory failure. Some conditions also involve other organ systems (eg, decreased digestive enzymes in CF or heart failure from cardiac involvement in Churg-Strauss syndrome).
Basic blood tests, imaging tests (ie, magnetic resonance imaging), and pulmonary function tests can all accelerate a diagnosis. Genetic tests are diagnostic for certain conditions, but often require a physician’s initial preliminary diagnosis. After diagnosis, other family members may need to be tested as well, depending on the condition. Genetic testing can help individuals make family planning decisions, as well.
Each lung disease requires its own treatment strategies to reduce symptoms, slow disease progess, or address root causes; these may include multiple components such as drugs, respiratory therapy, or a lung transplant.
Drug treatments may be approved for a specific condition or used off-label. Conditions that have received more research attention now have multiple treatment options, with many others in the research development pipeline (eg, PAH, HAE). Yet, for many of these rare lung diseases, there are few or no drugs currently specifically approved.
Some specific treatments for rare respiratory diseases include the following:
Complement C1 esterase inhibitor (Cinryze) to prevent attacks in HAE
Ecallantide (Kalbitor) to treat acute attacks in HAE
Macitentan (Opsumit) to delay disease progression in PAH
Riociguat (Adempas) to improve exercise capacity in PAH
Pirfenidone (Esbriet) to help decrease scarring in IPF
Aztreonam (Cayston) to improve symptoms in CF patients colonized by Pseudomonas aeruginosa
Numerous ongoing clinical trials designed to develop the next generation of orphan drug treatment for rare respiratory disorders are currently underway. A sampling of late-stage research, all in phase 3, includes studies of:
Hereditary Angioedema: BCX4161
Idiopathic pulmonary fibrosis: co-trimoxazole
PAH: sildenafil, udenafil
Pulmonary alveolar proteinosis: GM-CSF
Takayasu arteritis: tocilizumab
Advocacy Support and Information
Advocacy groups serve as an important resource for patients, caregivers, and clinicians, providing introductory educational materials and practical advice for dealing with these conditions, as well as more detailed information about recent research papers, current clinical trials, etc. They also provide social support and an avenue to learn from other families who have experience dealing with these diseases.
Below are some advocacy groups for rare pulmonary diseases: