Barbara Burton, MD, Attending Physician, Genetics, Birth Defects & Metabolism, Ann & Robert H. Lurie Children’s Hospital of Chicago, gives an overview of alpha mannosidosis.

As Dr. Burton explains, alpha mannosidosis is a multisystemic, mucopolysaccharidosis (MPS) disorder caused by a deficiency in the enzyme alpha-D-mannosidase. This enzyme is essential for metabolizing certain glycoproteins, and a deficiency allows these glycoproteins to abnormally accumulate in and damage various tissues and organs. 

The symptoms and severity of alpha mannosidosis are highly variable. Symptoms may include distinctive facial features (e.g., prominent forehead and jaw, and a flattened nose), skeletal abnormalities, hearing loss, intellectual disability, and dysfunction of the immune system. Alpha-mannosidosis is caused by an autosomal recessive mutation of the MAN2B1 gene.

Currently, treatment options for alpha mannosidosis include symptom management or hematopoietic stem cell transplantation (HSCT). While the enzyme replacement therapy, velmanase alfa, is approved in the European Union, it is currently not approved in the U.S.

To learn more about alpha mannosidosis and other lysosomal storage diseases, visit