Alpha-mannosidosis, a rare inherited disorder, affects multiple organs and tissues in the body.
Individuals with this condition may exhibit intellectual disability, distinctive facial features, and skeletal abnormalities, including reduced bone density, skull thickening, spinal deformations, knock knees, and joint deterioration. Other symptoms encompass difficulty in coordinating movements, muscle weakness, speech impairments, increased infection risk, liver and spleen enlargement, brain fluid buildup, hearing loss, and eye lens clouding. The severity of the disorder varies, with some experiencing rapid and severe neurological decline, leading to early childhood mortality, while others may have milder symptoms that appear later and progress slowly, enabling survival into adulthood. In the mildest cases, the condition may only be detected through laboratory testing, showing minimal or no noticeable symptoms.
Alpha-mannosidosis is caused by pathogenic (disease-causing) variants in the MAN2B1 gene and exhibits autosomal recessive inheritance. This means that both parents must be carriers to have a 25% chance to have a child with the condition.
Other names for this condition are alpha-D-mannosidosis, alpha-mannosidase B deficiency, alpha-mannosidase deficiency, deficiency of alpha-mannosidase, lysosomal alpha B mannosidosis, lysosomal alpha-D-mannosidase deficiency, and mannosidosis.