From OMIM
Alpha-mannosidosis is an autosomal recessive lysosomal storage disease characterized by mental retardation, coarse facial features, skeletal abnormalities, hearing impairment, neurologic motor problems, and immune deficiency. Expression of the disease varies considerably, and there is a wide spectrum of clinical findings and severity. Affected children are often normal at birth and during early development. They present in early childhood with delayed psychomotor development, delayed speech, and hearing loss. Additional features include large head with prominent forehead, rounded eyebrows, flattened nasal bridge, macroglossia, widely spaced teeth, dysostosis multiplex, and motor impairment (summary by Malm and Nilssen, 2008). Classification Systems Two classification systems have been used to describe the clinical presentation of alpha-mannosidosis. The earlier system delineated a more severe 'type I,' which shows infantile onset, rapid mental deterioration, hypotonia, splenomegaly, severe dysostosis multiplex, and severe recurrent infections, often resulting in death by age 8 years. Individuals with the less severe 'type II' show normal early development with later childhood development of mental retardation, hearing loss, coarse facies, neurologic deterioration, and survival well into adulthood (summary by Desnick et al., 1976 and Gotoda et al., 1998). A later classification system delineated 3 clinical types. Type 1 is the mildest form, with onset after age 10 years, without skeletal abnormalities and very slow progression. Type 2 is a moderate form, with onset before age 10 years, presence of skeletal abnormalities, and slow progression with development of ataxia by age 20 to 30 years. Type 3 is the severe form, with onset in early infancy, skeletal abnormalities, and obvious progression leading to early death from primary central nervous system involvement or myopathy. Most patients belong to clinical type 2 (summary by Malm and Nilssen, 2008). Despite the clinical heterogeneity of the disorder, there are no apparent genotype/phenotype correlations (Berg et al., 1999; Riise Stensland et al., 2012).  http://www.omim.org/entry/248500

From MedlinePlus Genetics
Alpha-mannosidosis is a rare inherited disorder that causes problems in many organs and tissues of the body. Affected individuals may have intellectual disability, distinctive facial features, and skeletal abnormalities. Characteristic facial features can include a large head, prominent forehead, low hairline, rounded eyebrows, large ears, flattened bridge of the nose, protruding jaw, widely spaced teeth, overgrown gums, and large tongue. The skeletal abnormalities that can occur in this disorder include reduced bone density (osteopenia), thickening of the bones at the top of the skull (calvaria), deformations of the bones in the spine (vertebrae), knock knees, and deterioration of the bones and joints.

Affected individuals may also experience difficulty in coordinating movements (ataxia); muscle weakness (myopathy); delay in developing motor skills such as sitting and walking; speech impairments; increased risk of infections; enlargement of the liver and spleen (hepatosplenomegaly); a buildup of fluid in the brain (hydrocephalus); hearing loss; and a clouding of the lens of the eye (cataract). Some people with alpha-mannosidosis experience psychiatric symptoms such as depression, anxiety, or hallucinations; episodes of psychiatric disturbance may be triggered by stressors such as having undergone surgery, emotional upset, or changes in routine.

The signs and symptoms of alpha-mannosidosis can range from mild to severe. The disorder may appear in infancy with rapid progression and severe neurological deterioration. Individuals with this early-onset form of alpha-mannosidosis often do not survive past childhood. In the most severe cases, an affected fetus may die before birth. Other individuals with alpha-mannosidosis experience milder signs and symptoms that appear later and progress more slowly. People with later-onset alpha-mannosidosis may survive into their fifties. The mildest cases may be detected only through laboratory testing and result in few if any symptoms.  https://medlineplus.gov/genetics/condition/alpha-mannosidosis