Shwachman syndrome is a rare genetic disorder with multiple and varied manifestations. The disorder is typically characterized by signs of insufficient absorption (malabsorption) of fats and other nutrients due to abnormal development of the pancreas (pancreatic insufficiency) and improper functioning of the bone marrow (bone marrow dysfunction), resulting in low levels of circulating blood cells (hematologic abnormalities). Additional characteristic findings may include short stature; abnormal bone development affecting the rib cage and/or bones in the arms and/or legs (metaphyseal dysostosis); and/or liver abnormalities.
Due to abnormal skeletal changes, individuals with Shwachman syndrome may have abnormal thickening of the ribs and their supporting connective tissue (costochondral thickening), resulting in unusually short, flared ribs. In addition, improper bone development (abnormal ossification) within the arms and/or legs (limbs) may cause growth delay in particular bones. Many children with Shwachman syndrome may also be smaller than expected for their ages, with below average height (short stature) and weight. Although malabsorption due to pancreatic insufficiency may itself cause problems with growth and nutrition, short stature appears to be one of the many primary manifestations of Shwachman syndrome.
In addition, as a result of bone marrow dysfunction, individuals with Shwachman syndrome may have a decrease in any or all types of blood cells. Therefore, they may have low levels of certain white blood cells (neutropenia), platelets (thrombocytopenia), red blood cells (anemia), and/or all types of blood cells (pancytopenia). Neutropenia is the most common blood abnormality associated with Shwachman syndrome. Because neutrophils, a type of white blood cell, play an essential role in fighting bacterial infections, many affected individuals are prone to repeated bacterial infections (e.g., recurrent respiratory infections [pneumonia] and infections of the middle ear [otitis media]); in some cases, infections may be severe.
Some affected individuals may also have abnormal enlargement of the liver (hepatomegaly), increased levels of certain liver enzymes in the blood, and/or other findings in association with the disorder. Shwachman syndrome is believed to be inherited as an autosomal recessive trait.