Miscellaneous Conditions

Miscellaneous conditions include Hermansky-Pudlak syndrome (HPS), Niemann-Pick (NP) and Gaucher diseases, dyskeratosis congenita (DC), pulmonary alveolar microlithiasis (PAM), pulmonary alveolar proteinosis (PAP), pulmonary hyalinizing granuloma (PHG), and IgG4-sclerosing disease. HPS is a rare autosomal recessive disorder characterized by oculocutaneous albinism, bleeding diathesis, and granulomatous colitis. NP and Gaucher diseases are rare lysosomal storage disorders, inherited in an autosomal recessive manner, that result in accumulation of lipid compounds in various organs. NP disease is associated with acid sphingomyelinase deficiency and Gaucher disease with deficient activity of the lysosomal enzyme glucocerebrosidase. DC, a congenital disease associated with telomere-mediated disorders, is actually recognized as a syndrome of telomere shortening, characterized by manifestations in multiple organs with the highest morbidity and mortality related to failure of the bone marrow, lung, and liver. PAM is an autosomal recessive disorder characterized by intra-alveolar accumulation of calcium phosphate deposits, called microliths, as a result of the inability of type II alveolar epithelial cells to clear phosphorus ions from the alveolar space, leading to microlith or calcospherite formation in the extracellular fluid. PAP manifests with progressive dyspnea caused by the accumulation of surfactant in pulmonary alveoli due to either defect in surfactant clearance or abnormal production. Primary PAP can be classified as autoimmune (most common type, 90% of the cases) or hereditary. Secondary PAP is seen in multiple diseases that affect macrophage function in the alveoli. PHG is an unusual pathological condition of unknown etiology although it may have an autoimmune origin. In some cases, PHG may be also associated with similar histological conditions such as retroperitoneal fibrosis and sclerosing mediastinitis. IgG4-sclerosing disease appears to be part of a more systemic process with an increased production of IgG4.