Orphan Lung Diseases

Jay H. Ryu, MD

Luca Richeldi, MD

February 29, 2016, the ninth International Rare Disease day was held around the world. The slogan for this year was “Join us in making the voice of rare diseases heard.” There are over 6,000 orphan (rare) diseases that can afflict humans. An orphan disease affects 1 in 1,600 to 2,500 people, depending on varying definitions used around the globe. An estimated 25 million people in the United States have orphan diseases, while in Europe 30 million are affected. Orphan diseases pose a heavy public health burden worldwide. Patients with orphan diseases may experience difficulties in accessing high-quality health care related to incorrect or delayed diagnosis, scarcity of relevant scientific knowledge and expertise, and lack of effective treatment.

Remarkable advances continue to be achieved in orphan diseases, in part, due to progress in human genetics. This is also true of orphan lung diseases. In recent years, effective treatment has been formulated for several orphan lung diseases, including lymphangioleiomyomatosis, pulmonary alveolar proteinosis, and idiopathic pulmonary fibrosis. Optimism continues to rise in achieving similar feats in other orphan lung diseases.

This issue of Seminars in Respiratory and Critical Care Medicine is devoted to orphan lung diseases in describing the recent advances in this field, current state-of-the-art, and the road ahead. First, several articles focused on idiopathic interstitial pneumonias, including idiopathic pulmonary fibrosis (IPF). Interstitial pneumonias comprise a large portion of interstitial lung diseases. Chu and colleagues describe the contribution of candidate gene approaches and genome-wide association studies toward better understanding of pathobiology in idiopathic interstitial pneumonias. Torrisi et al focus on the pathogenesis of IPF, the most common form of idiopathic interstitial pneumonia. Clinical aspects of IPF, including the role of lung transplantation, are summarized by Lynch et al. In the past year, effective pharmacologic therapy has been identified in the treatment of IPF and is discussed by Antoniou and colleagues.

Idiopathic nonspecific interstitial pneumonia (NSIP) can be difficult to distinguish from IPF but is associated with a better prognosis. Tomassetti and colleagues discuss NSIP and current approaches to management. Hypersensitivity pneumonitis can also be confused with IPF as well as NSIP. Morrell et al describe the challenges in diagnosing hypersensitivity pneumonitis and optimal management.

There are many other orphan lung diseases, some of which are discussed in the remaining articles in this issue. Arcadu et al provide an update on lymphoid interstitial pneumonia, a rare type of idiopathic interstitial pneumonia, and other benign lymphoid disorders of the lung including IgG4-related disease. Cordier and colleagues review a wide array of disorders that can affect the bronchioles. Sergew and Fernández-Perez describe various forms of eosinophilic lung diseases. Diagnostic approach to diffuse cystic lung diseases is outlined by Xu and colleagues. In recent years, it has become apparent that many diseases beyond lymphangioleiomyomatosis and pulmonary Langerhans cell histiocytosis can cause diffuse cystic lung disease. Aparicio and Lee discuss the manifestations of connective tissue diseases in the lung and the challenges in the management of these patients which requires a thoughtful multidisciplinary integration. The final article in this issue is provided by Jones and Richeldi, who focus on the road ahead and the future needs in interstitial lung diseases.

In closing, we wish to express our thanks to the distinguished authors for their contributions to this issue of Seminars in Respiratory and Critical Care Medicine and recognize their accomplishments in helping us better understand these orphan lung diseases. We hope the readers come away with a sense of optimism that the rarity of these diseases has not prevented meaningful advances that have led to new effective treatments and improved the lives of patients with these disorders.