The severe form of the disease is called typical mucolipidosis IV, and the mild form is called atypical mucolipidosis IV. Approximately 95 percent of individuals diagnosed with this condition have the severe form.
The symptoms and physical findings associated with mucolipidosis IV are usually apparent within three to eight months following birth. The first recognized symptoms are usually clouding (opacity) of the cornea and eye movement abnormalities. In some cases, these symptoms may be overlooked until three to five years of age.
Most affected infants exhibit hypotonia, moderate to severe intellectual disability, delays in reaching developmental milestones, and/or significant psychomotor retardation.
In addition, individuals with mucolipidosis IV may have abnormalities affecting the eyes including crossed eyes (strabismus), puffy eyelids, degeneration of the nerve-rich membrane lining the eyes (retina), and/or Visual impairment (amblyopia) in an eye that appears structurally normal. In some cases, such eye abnormalities may result in an abnormal Sensitivity to light (photophobia) and/or Nearsightedness (myopia).
Individuals with mucolipidosis IV develop iron deficiency anemia because their stomachs do not secrete acid. They do not have enlarged livers or spleens, skeletal involvement, or mucopolysaccharides in the urine.
Patients exhibit accumulation of certain fatty substances (lipids) and certain complex carbohydrates (mucopolysaccharides) within the cells of many tissues of the body. Those appear as large vacuoles and fluorescent vesicles in patient cells.