Immunodeficiency-43 (IMD43) is an autosomal recessive immunologic disorder characterized by decreased or absent expression of MHC class I molecules on the cell surface. Most affected individuals develop recurrent bacterial respiratory tract infections in childhood or adulthood, which may progress to bronchiectasis, and about half develop ulcerating or necrotizing granulomatous inflammatory skin lesions. Laboratory studies show decreased numbers of B cells, hypogammaglobulinemia, hypoproteinemia, and decreased alpha-beta CD8+ T cells with increased gamma-delta CD8+ T cells. The severity is variable, and some individuals may be asymptomatic (summary by Ardeniz et al., 2015). For a discussion of genetic heterogeneity of MHC class I deficiency, see MHC1D1 (604571).

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.