NKX2-1-related disorders range from benign hereditary chorea (BHC) to choreoathetosis, congenital hypothyroidism, and neonatal respiratory distress (also known as brain-lung-thyroid syndrome). Childhood-onset chorea, the hallmark of NKX2-1-related disorders, may or may not be associated with respiratory distress syndrome or congenital hypothyroidism. Chorea generally begins in early infancy or about age one year (most commonly) or in late childhood or adolescence, and progresses into the second decade after which it remains static or (rarely) remits. Pulmonary disease, the second most common manifestation, can include respiratory distress syndrome in neonates, interstitial lung disease in young children, and pulmonary fibrosis in older persons. The risk for pulmonary carcinoma is increased in young adults with an NKX2-1-related disorder. Thyroid dysfunction, the result of dysembryogenesis, can present as congenital hypothyroidism or compensated hypothyroidism. The risk for thyroid cancer is unknown and may not be increased. In one review, 50% of affected individuals had the full brain-lung-thyroid syndrome, 30% had involvement of brain and thyroid only, and 13% had isolated chorea only.

Granulomatosis with polyangiitis, formerly termed Wegener granulomatosis, is a systemic disease with a complex genetic background. It is characterized by necrotizing granulomatous inflammation of the upper and lower respiratory tract, glomerulonephritis, vasculitis, and the presence of antineutrophil cytoplasmatic autoantibodies (ANCAs) in patient sera. These ANCAs are antibodies to a defined target antigen, proteinase-3 (PR3, PRTN3; 177020), which is present within primary azurophil granules of neutrophils (PMNs) and lysozymes of monocytes. On cytokine priming of PMNs, PR3 translocates to the cell surface, where PR3-ANCAs can interact with their antigens and activate PMNs. PMNs from patients with active GPA express PR3 on their surface, produce respiratory burst, and release proteolytic enzymes after activation with PR3-ANCAs. The consequence is a self-sustaining inflammatory process (Jagiello et al., 2004).

Interstitial lung disease (ILD) comprises a heterogeneous group of rare diseases affecting the distal part of the lung and characterized by a progressive remodeling of the alveolar interstitium. The manifestations form a spectrum ranging from idiopathic interstitial pneumonia (IIP) or pneumonitis to the more severe idiopathic pulmonary fibrosis (IPF). IPF is associated with an increased risk of developing lung cancer, which occurs in a subset of patients with ILD. Clinical features of ILD include dyspnea, clubbing of the fingers, and restrictive lung capacity. Imaging typically shows ground glass opacities and inter- and intraseptal thickening, while histologic studies usually show a pattern consistent with 'usual interstitial pneumonia' (UIP) (review by Gross and Hunninghake, 2001; summary by Legendre et al., 2020). Idiopathic pulmonary fibrosis is one of a family of idiopathic pneumonias sharing clinical features of shortness of breath, radiographically evident diffuse pulmonary infiltrates, and varying degrees in inflammation, fibrosis, or both on lung biopsy. In some cases, the disorder can be rapidly progressive and characterized by sequential acute lung injury with subsequent scarring and end-stage lung disease. Although older studies included several forms of interstitial pneumonia under the term 'idiopathic pulmonary fibrosis,' the clinical label of 'idiopathic pulmonary fibrosis' should be reserved for patients with a specific form of fibrosing interstitial pneumonia referred to as usual interstitial pneumonia (Gross and Hunninghake, 2001). It is estimated that 0.5 to 2.2% of cases of idiopathic pulmonary fibrosis are familial (Marshall et al., 2000). Gross and Hunninghake (2001) reviewed idiopathic pulmonary fibrosis, emphasizing definition, pathogenesis, diagnosis, natural history, and therapy. Antoniou et al. (2004) provided a 'top ten list' of references pertaining to etiopathogenesis, prognosis, diagnosis, therapy, and other aspects of idiopathic pulmonary fibrosis. For a discussion of genetic heterogeneity of ILD, see ILD1 (619611). Pulmonary fibrosis can also be a feature in patients with mutations in the TERT (187270) or the TERC (602322) gene; see PFBMFT1 (614742) and PFBMFT2 (614743). Some patients with surfactant protein C deficiency (610913) who survive to adulthood manifest features of pulmonary fibrosis.

Interstitial lung disease (ILD) comprises a heterogeneous group of rare diseases affecting the distal part of the lung and characterized by a progressive remodeling of the alveolar interstitium. The manifestations form a spectrum ranging from idiopathic interstitial pneumonia (IIP) or pneumonitis to the more severe idiopathic pulmonary fibrosis (IPF). IPF is associated with an increased risk of developing lung cancer, which occurs in a subset of patients with ILD. Clinical features of ILD include dyspnea, clubbing of the fingers, and restrictive lung capacity. Imaging typically shows ground glass opacities and inter- and intraseptal thickening, while histologic studies usually show a pattern consistent with 'usual interstitial pneumonia' (UIP) (summary by Nathan et al., 2016, Doubkova et al., 2019). Genetic Heterogeneity of Interstitial Lung Disease See also ILD2 (178500), caused by mutation in the SFTPA2 gene (178642) on chromosome 10q22.