Alpha-1 antitrypsin deficiency (AATD) can present with hepatic dysfunction in individuals from infancy to adulthood and with chronic obstructive lung disease (emphysema and/or bronchiectasis), characteristically in individuals older than age 30 years. Individuals with AATD are also at increased risk for panniculitis (migratory, inflammatory, tender skin nodules which may ulcerate on legs and lower abdomen) and C-ANCA-positive vasculitis (granulomatosis with polyangiitis). Phenotypic expression varies within and between families. In adults, smoking is the major factor in accelerating the development of COPD; nonsmokers may have a normal life span, but can also develop lung and/or liver disease. Although reported, emphysema in children with AATD is extremely rare. AATD-associated liver disease, which is present in only a small portion of affected children, manifests as neonatal cholestasis. The incidence of liver disease increases with age. Liver disease in adults (manifesting as cirrhosis and fibrosis) may occur in the absence of a history of neonatal or childhood liver disease. The risk for hepatocellular carcinoma (HCC) is increased in individuals with AATD.

Interstitial lung disease (ILD), or pneumonitis, is a heterogeneous group of disorders characterized pathologically by expansion of the interstitial compartment of the lung by inflammatory cells. Fibrosis occurs in many cases (Visscher and Myers, 2006). See also interstitial lung disease-1 (ILD1; 619611). Desquamative interstitial pneumonitis (DIP) was originally described as a pathologic entity by Liebow et al. (1965). Lung biopsy shows diffuse and uniform filling of alveoli by clusters of cells which Liebow et al. (1965) speculated to be 'desquamated pneumocytes.' Since then, these cells have been shown primarily to be pigmented alveolar macrophages. Other features include thickened alveolar septa with an infiltrate of inflammatory cells and plump, cuboidal type II pneumocytes. Mild collagen deposition without architectural distortion or honeycombing may be present. Different forms of ILD represent pathologic classifications based on histologic patterns rather than clinical diagnoses and may occur in a variety of clinical contexts (Visscher and Myers, 2006). Although DIP occurs most often as a sporadic disorder in adults during the third to fifth decade of life and is highly associated with smoking (Carrington et al., 1978), reports of a familial form with onset in infancy and early death suggest a genetic basis (Sharief et al., 1994). Cases of DIP reported in infants are often more severe and refractory to treatment than those reported in adults (Nogee et al., 2001).

Gaucher disease (GD) encompasses a continuum of clinical findings from a perinatal lethal disorder to an asymptomatic type. The identification of three major clinical types (1, 2, and 3) and two other subtypes (perinatal-lethal and cardiovascular) is useful in determining prognosis and management. GD type 1 is characterized by the presence of clinical or radiographic evidence of bone disease (osteopenia, focal lytic or sclerotic lesions, and osteonecrosis), hepatosplenomegaly, anemia and thrombocytopenia, lung disease, and the absence of primary central nervous system disease. GD types 2 and 3 are characterized by the presence of primary neurologic disease; in the past, they were distinguished by age of onset and rate of disease progression, but these distinctions are not absolute. Disease with onset before age two years, limited psychomotor development, and a rapidly progressive course with death by age two to four years is classified as GD type 2. Individuals with GD type 3 may have onset before age two years, but often have a more slowly progressive course, with survival into the third or fourth decade. The perinatal-lethal form is associated with ichthyosiform or collodion skin abnormalities or with nonimmune hydrops fetalis. The cardiovascular form is characterized by calcification of the aortic and mitral valves, mild splenomegaly, corneal opacities, and supranuclear ophthalmoplegia. Cardiopulmonary complications have been described with all the clinical subtypes, although varying in frequency and severity.

Pulmonary venoocclusive disease-2 is an autosomal recessive subtype of primary pulmonary hypertension (PPH; see 178600). It is characterized histologically by widespread fibrous intimal proliferation of septal veins and preseptal venules, and is frequently associated with pulmonary capillary dilatation and proliferation. The disorder can cause occult alveolar hemorrhage. High-resolution CT imaging of the chest shows patchy centrilobular ground-glass opacities, septal lines, and lymph node enlargement (summary by Eyries et al., 2014). For a discussion of genetic heterogeneity of pulmonary venoocclusive disease, see PVOD1 (265450).

A rare, fulminant small vessel vasculitis that affects the capillary beds of the kidneys and lungs and characterized by the presence of anti-glomerular basement membrane (GBM) and, in its full-blown form, anti-alveolar basement membrane (ABM) antibodies. Consequently, it may manifest as a rapidly progressive, isolated glomerulonephritis (anti-GBM nephritis) or as a pulmonary-renal syndrome with severe lung hemorrhage.

Diffuse panbronchiolitis (DPB) is a rare chronic inflammatory obstructive pulmonary disease primarily affecting the respiratory bronchioles. 'Diffuse' refers to the distribution of the lesions throughout both lungs, and 'pan-' refers to the involvement of inflammation in all layers of the respiratory bronchioles. Onset of the disorder occurs in the second to fifth decade of life, and is clinically manifest by chronic cough, exertional dyspnea, and sputum production. Most patients also have chronic paranasal sinusitis. If untreated, the disorder progresses to bronchiectasis, respiratory failure, and death (summary by Poletti et al., 2006).

The hereditary sensory and autonomic neuropathies (HSAN), which are also referred to as hereditary sensory neuropathies (HSN) in the absence of significant autonomic features, are a genetically and clinically heterogeneous group of disorders associated with sensory dysfunction. For a discussion of genetic heterogeneity of HSAN, see HSAN1A (162400).

Chronic granulomatous disease (CGD) is a primary immunodeficiency disorder of phagocytes (neutrophils, monocytes, macrophages, and eosinophils) resulting from impaired killing of bacteria and fungi. CGD is characterized by severe recurrent bacterial and fungal infections and dysregulated inflammatory responses resulting in granuloma formation and other inflammatory disorders such as colitis. Infections typically involve the lung (pneumonia), lymph nodes (lymphadenitis), liver (abscess), bone (osteomyelitis), and skin (abscesses or cellulitis). Granulomas typically involve the genitourinary system (bladder) and gastrointestinal tract (often the pylorus initially, and later the esophagus, jejunum, ileum, cecum, rectum, and perirectal area). Some males with X-linked CGD have McLeod neuroacanthocytosis syndrome as the result of a contiguous gene deletion. While CGD may present anytime from infancy to late adulthood, the vast majority of affected individuals are diagnosed before age five years. Use of antimicrobial prophylaxis and therapy has greatly improved overall survival.

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.

For a general phenotypic description and a discussion of genetic heterogeneity of pulmonary surfactant metabolism dysfunction, see SMDP1 (265120).

Pulmonary surfactant metabolism dysfunction-2 (SMDP2) is a rare autosomal dominant disease associated with progressive respiratory insufficiency and lung disease with a variable clinical course. The pathophysiology of the disorder is postulated to involve intracellular accumulation of a structurally defective SPC protein (Thomas et al., 2002). For a general phenotypic description and a discussion of genetic heterogeneity of pulmonary surfactant metabolism dysfunction, see SMDP1 (265120).

Pulmonary alveolar proteinosis is a pathologic entity characterized by intraalveolar surfactant accumulation. There are 3 clinically distinct forms: hereditary (usually congenital), secondary, and acquired. The acquired form of pulmonary alveolar proteinosis is the most common form, accounting for approximately 90% of cases. The mean age at diagnosis is 39 years and it is associated with smoking in 72% of cases. The estimated incidence and prevalence are 0.36 and 3.70 cases per million, respectively (Trapnell et al., 2003; Seymour and Presneill, 2002). Secondary pulmonary alveolar proteinosis develops in association with conditions involving functional impairment or reduced numbers of alveolar macrophages. Such conditions include some hematologic cancers, pharmacologic immunosuppression, inhalation of inorganic dust or toxic fumes, and certain infections. Congenital pulmonary alveolar proteinosis is a rare, severe, often fatal disorder of newborns associated with pulmonary surfactant metabolism dysfunction caused by mutations in genes involved in surfactant metabolism (see, e.g., SMDP1, 265120) (Trapnell et al., 2003). See 300770 for information on congenital PAP due to CSF2RA (306250) deficiency.

Primary ciliary dyskinesia is an autosomal recessive disorder resulting from loss of normal ciliary function. Kartagener (pronounced KART-agayner) syndrome is characterized by the combination of primary ciliary dyskinesia and situs inversus, and occurs in approximately half of patients with ciliary dyskinesia. Since normal nodal ciliary movement in the embryo is required for normal visceral asymmetry, absence of normal ciliary movement results in a lack of definitive patterning; thus, random chance alone appears to determine whether the viscera take up the normal or reversed left-right position during embryogenesis. This explains why approximately 50% of patients, even within the same family, have situs inversus (Afzelius, 1976; El Zein et al., 2003). For a general description and a discussion of genetic heterogeneity of primary ciliary dyskinesia and Kartagener syndrome, see CILD1 (244400).

Primary ciliary dyskinesia is an autosomal recessive disorder resulting from loss of normal ciliary function. Kartagener (pronounced KART-agayner) syndrome is characterized by the combination of primary ciliary dyskinesia and situs inversus, and occurs in approximately half of patients with ciliary dyskinesia. Since normal nodal ciliary movement in the embryo is required for normal visceral asymmetry, absence of normal ciliary movement results in a lack of definitive patterning; thus, random chance alone appears to determine whether the viscera take up the normal or reversed left-right position during embryogenesis. This explains why approximately 50% of patients, even within the same family, have situs inversus (Afzelius, 1976; El Zein et al., 2003). For a general phenotypic description and a discussion of genetic heterogeneity of primary ciliary dyskinesia and the Kartagener syndrome, see CILD1 (244400).

Any sarcoidosis in which the cause of the disease is a mutation in the HLA-DRB1 gene.

Primary ciliary dyskinesia-14 (CILD14) is an autosomal recessive disorder characterized by recurrent respiratory infections associated with defects in ciliary inner dynein arms and axonemal disorganization (Merveille et al., 2011). For a general phenotypic description and a discussion of genetic heterogeneity of primary ciliary dyskinesia, see CILD1 (244400).

Primary ciliary dyskinesia-15 (CILD15) is an autosomal recessive disorder characterized by recurrent respiratory infections associated with defects in ciliary inner dynein arms and axonemal disorganization (summary by Becker-Heck et al., 2011). For a general phenotypic description and a discussion of genetic heterogeneity of primary ciliary dyskinesia, see CILD1 (244400).

IMD31C is a disorder of immunologic dysregulation with highly variable manifestations resulting from autosomal dominant gain-of-function mutations in STAT1 (600555). Most patients present in infancy or early childhood with chronic mucocutaneous candidiasis (CMC). Other highly variable features include recurrent bacterial, viral, fungal, and mycoplasmal infections, disseminated dimorphic fungal infections, enteropathy with villous atrophy, and autoimmune disorders, such as hypothyroidism or diabetes mellitus. A subset of patients show apparently nonimmunologic features, including osteopenia, delayed puberty, and intracranial aneurysms. Laboratory studies show increased activation of gamma-interferon (IFNG; 147570)-mediated inflammation (summary by Uzel et al., 2013 and Sampaio et al., 2013).

Cerebellar ataxia, neuropathy, and vestibular areflexia syndrome (CANVAS) is an autosomal recessive adult-onset, slowly progressive neurologic disorder characterized by imbalance due to cerebellar gait and limb ataxia, impaired vestibular function bilaterally, and non-length-dependent sensory neuropathy (summary by Szmulewicz et al., 2011).

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).

Primary ciliary dyskinesia-17 is an autosomal recessive disorder characterized by early infantile onset of respiratory distress associated with a defect in the function of ciliary outer dynein arms. Situs inversus is variable (summary by Panizzi et al., 2012). For a general phenotypic description and a discussion of genetic heterogeneity of primary ciliary dyskinesia, see CILD1 (244400).

Dyskeratosis congenita and related telomere biology disorders (DC/TBD) are caused by impaired telomere maintenance resulting in short or very short telomeres. The phenotypic spectrum of telomere biology disorders is broad and includes individuals with classic dyskeratosis congenita (DC) as well as those with very short telomeres and an isolated physical finding. Classic DC is characterized by a triad of dysplastic nails, lacy reticular pigmentation of the upper chest and/or neck, and oral leukoplakia, although this may not be present in all individuals. People with DC/TBD are at increased risk for progressive bone marrow failure (BMF), myelodysplastic syndrome or acute myelogenous leukemia, solid tumors (usually squamous cell carcinoma of the head/neck or anogenital cancer), and pulmonary fibrosis. Other findings can include eye abnormalities (epiphora, blepharitis, sparse eyelashes, ectropion, entropion, trichiasis), taurodontism, liver disease, gastrointestinal telangiectasias, and avascular necrosis of the hips or shoulders. Although most persons with DC/TBD have normal psychomotor development and normal neurologic function, significant developmental delay is present in both forms; additional findings include cerebellar hypoplasia (Hoyeraal Hreidarsson syndrome) and bilateral exudative retinopathy and intracranial calcifications (Revesz syndrome and Coats plus syndrome). Onset and progression of manifestations of DC/TBD vary: at the mild end of the spectrum are those who have only minimal physical findings with normal bone marrow function, and at the severe end are those who have the diagnostic triad and early-onset BMF.

Any primary ciliary dyskinesia in which the cause of the disease is a mutation in the CCDC151 gene.

Primary ciliary dyskinesia-33 is an autosomal recessive disorder characterized by recurrent upper and lower respiratory infections due to defective ciliary clearance and resulting in chronic lung disease. Some patients may have recurrent ear infections resulting in conductive hearing impairment. Examination of respiratory cilia shows subtle movement defects. Laterality defects have not been reported (summary by Olbrich et al., 2015). For a phenotypic description and a discussion of genetic heterogeneity of primary ciliary dyskinesia, see CILD1 (244400).

Dyskeratosis congenita and related telomere biology disorders (DC/TBD) are caused by impaired telomere maintenance resulting in short or very short telomeres. The phenotypic spectrum of telomere biology disorders is broad and includes individuals with classic dyskeratosis congenita (DC) as well as those with very short telomeres and an isolated physical finding. Classic DC is characterized by a triad of dysplastic nails, lacy reticular pigmentation of the upper chest and/or neck, and oral leukoplakia, although this may not be present in all individuals. People with DC/TBD are at increased risk for progressive bone marrow failure (BMF), myelodysplastic syndrome or acute myelogenous leukemia, solid tumors (usually squamous cell carcinoma of the head/neck or anogenital cancer), and pulmonary fibrosis. Other findings can include eye abnormalities (epiphora, blepharitis, sparse eyelashes, ectropion, entropion, trichiasis), taurodontism, liver disease, gastrointestinal telangiectasias, and avascular necrosis of the hips or shoulders. Although most persons with DC/TBD have normal psychomotor development and normal neurologic function, significant developmental delay is present in both forms; additional findings include cerebellar hypoplasia (Hoyeraal Hreidarsson syndrome) and bilateral exudative retinopathy and intracranial calcifications (Revesz syndrome and Coats plus syndrome). Onset and progression of manifestations of DC/TBD vary: at the mild end of the spectrum are those who have only minimal physical findings with normal bone marrow function, and at the severe end are those who have the diagnostic triad and early-onset BMF.

Interstitial lung and liver disease is an autosomal recessive disorder characterized by onset of respiratory insufficiency and progressive liver disease in infancy or early childhood. Pathologic examination of lung lavage is consistent with pulmonary alveolar proteinosis (summary by Hadchouel et al., 2015).

CILD36 is an X-linked recessive disorder characterized by chronic airway disease and recurrent sinopulmonary infections beginning in childhood and caused by defective ciliary function. Affected individuals also have infertility due to defective sperm flagella. About half of patients have laterality defects due to ciliary dysfunction at the embryonic node (summary by Paff et al., 2017). For a phenotypic description and a discussion of genetic heterogeneity of primary ciliary dyskinesia, see CILD1 (244400).

Primary pulmonary arterial hypertension is a rare, often fatal, progressive vascular lung disease characterized by increased pulmonary vascular resistance and sustained elevation of mean pulmonary arterial pressure, leading to right ventricular hypertrophy and right heart failure. Pathologic features include a narrowing and thickening of small pulmonary vessels and plexiform lesions. There is pulmonary vascular remodeling of all layers of pulmonary arterial vessels: intimal thickening, smooth muscle cell hypertrophy or hyperplasia, adventitial fibrosis, and occluded vessels by in situ thrombosis (summary by Machado et al., 2009 and Han et al., 2013). Heterozygous mutations in the BMPR2 gene are found in nearly 70% of families with heritable PPH and in 25% of patients with sporadic disease. The disease is more common in women (female:male ratio of 1.7:1). However, the penetrance of PPH1 is incomplete: only about 10 to 20% of individuals with BMPR2 mutations develop the disease during their lifetime, suggesting that development of the disorder is triggered by other genetic or environmental factors. Patients with PPH1 are less likely to respond to acute vasodilater testing and are unlikely to benefit from treatment with calcium channel blockade (summary by Machado et al., 2009 and Han et al., 2013). Genetic Heterogeneity of Primary Pulmonary Hypertension See also PPH2 (615342), caused by mutation in the SMAD9 gene (603295) on chromosome 13q13; PPH3 (615343), caused by mutation in the CAV1 gene (601047) on chromosome 7q31; PPH4 (615344), caused by mutation in the KCNK3 gene (603220) on chromosome 2p23; PPH5 (265400), caused by mutation in the ATP13A3 gene (610232) on chromosome 3q29; and PPH6 (620777), caused by mutation in the CAPNS1 gene (114170) on chromosome 19q13. Primary pulmonary hypertension may also be found in association with hereditary hemorrhagic telangiectasia type 1 (HHT1; 187300), caused by mutation in the ENG gene (131195), and HHT2 (600376), caused by mutation in the ACVRL1 (ALK1) gene (601284). Pediatric-onset pulmonary hypertension may be seen in association with ischiocoxopodopatellar syndrome (ICPPS; 147891). The skeletal manifestations of ICPPS are highly variable and may not be detected in children. Parents are not likely to have PAH (Levy et al., 2016).

Primary ciliary dyskinesia-39 (CILD39) is an autosomal recessive disorder characterized by chronic sinopulmonary infections beginning soon after birth and laterality defects in about 50% of patients. Although patient nasal ciliary samples have normal structure, detailed studies may show ciliary kinetic defects in some patients (summary by Bonnefoy et al., 2018). For a phenotypic description and a discussion of genetic heterogeneity of primary ciliary dyskinesia, see 244400.

Primary ciliary dyskinesia-40 (CILD40) is an autosomal recessive disorder with a relatively mild respiratory phenotype compared to other CILDs. Patients present in childhood with mild upper respiratory symptoms and infections, but typically do not develop serious lung disease. Nitric oxide levels are low-normal or normal. All reported patients have had situs inversus, including several with severe congenital cardiac malformations, but left-right body asymmetry is still theoretically random and would occur in 50% of patients (summary by Loges et al., 2018). For a discussion of genetic heterogeneity of primary ciliary dyskinesia and Kartagener syndrome, see CILD1 (244400).

Autoimmune interstitial lung, joint, and kidney disease is an autosomal dominant systemic autoimmune disorder characterized by interstitial lung disease, inflammatory arthritis, and immune complex-mediated renal disease. Laboratory studies show high-titer autoantibodies. Symptoms appear in the first 2 decades of life, but there is incomplete penetrance (summary by Watkin et al., 2015).

Rajab interstitial lung disease with brain calcifications-1 (RILCBC1) is an autosomal recessive multisystem disorder with a highly variable phenotype. Most patients present in infancy or early childhood with poor growth and interstitial lung disease, which may lead to death. Some may also have liver, skeletal, and renal abnormalities, and most have intracranial calcifications on brain imaging. Some may have early impaired motor development, but most have normal cognitive development (summary by Xu et al., 2018). Genetic Heterogeneity of Rajab Interstitial Lung Disease with Brain Calcifications Also see Rajab interstitial disease with brain calcifications-2 (RILDBC2; 619013), caused by mutation in the FARSA gene (602918).

Rajab interstitial lung disease with brain calcifications-2 (RILDBC2) is an autosomal recessive disorder characterized by growth delay, interstitial lung disease, liver disease, and abnormal brain MRI findings, including brain calcifications and periventricular cysts (Krenke et al., 2019). For a discussion of genetic heterogeneity of RILDBC, see RILDBC1 (613658).

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.

Nephronophthisis-like nephropathy-2 (NPHPL2) is an autosomal recessive cystic kidney disease characterized by onset of progressive renal insufficiency in the first decades of life. Renal imaging and biopsy show corticomedullary cysts, tubular ectasia, tubular basement membrane disruption, and tubulointerstitial infiltrations. Patients eventually progress to end-stage renal failure, necessitating kidney transplantation or dialysis (summary by Hurd et al., 2013). For a general phenotypic description and a discussion of genetic heterogeneity of nephronophthisis, see NPHP1 (256100).

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.

Visceral heterotaxy-10 (HTX10) is characterized by a failure to generate normal left-right visceral asymmetry during embryogenesis, which can result in heterotaxy syndrome or situs inversus totalis. Affected individuals may experience mild chronic respiratory symptoms, but do not fulfill the criteria for primary ciliary dyskinesia (see 244400). Male infertility has been reported (Ta-Shma et al., 2015; Dougherty et al., 2020). For a discussion of genetic heterogeneity of visceral heterotaxy, see HTX1 (306955).

Severe congenital liver disease (SCOLIV) is an autosomal recessive disorder characterized by the onset of progressive hepatic dysfunction usually in the first years of life. Affected individuals show feeding difficulties with failure to thrive and features such as jaundice, hepatomegaly, and abdominal distension. Laboratory workup is consistent with hepatic insufficiency and may also show coagulation defects, anemia, or metabolic disturbances. Cirrhosis and hypernodularity are commonly observed on liver biopsy. Many patients die of liver failure in early childhood (Moreno Traspas et al., 2022).

Primordial dwarfism-immunodeficiency-lipodystrophy syndrome (PDIL) is characterized by pre- and postnatal growth restriction, with extreme microcephaly, short stature, and absence of subcutaneous fat. There is also significant hematologic/immune dysfunction, with hypo- or agammaglobulinemia, as well as lymphopenia, anemia, and thrombocytopenia, and most affected individuals succumb to infection in early childhood (Parry et al., 2020).

Recurrent respiratory infections and failure to thrive with or without diarrhea (RIFTD) is characterized by neonatal onset of chronic cough, episodic wheezing, recurrent lower respiratory tract infections, chronic diarrhea, and failure to thrive. Despite the resemblance to cystic fibrosis (CF; 219700), these patients have normal sweat chloride and pancreatic elastase tests (Bertoli-Avella et al., 2022).