Imerslund-Grasbeck syndrome type 1

An autosomal recessive disorder characterized by onset of megaloblastic anemia associated with decreased serum vitamin B12 (cobalamin, Cbl) in infancy or early childhood. Low molecular weight (LMW) proteinuria is frequently present, but sometimes occurs later and is usually mild or subclinical. Patients often present with vague symptoms, including failure to thrive, loss of appetite, fatigue, lethargy, and/or recurrent infections. Some patients may present later in childhood with neurologic abnormalities related to B12 deficiency, such as sensorimotor neuropathy and/or cognitive disturbances.