Types of ML4

Typical “Classic” Mucolipidosis Type IV (ML4)

  • Psychomotor retardation, similar to cerebral palsy
  • Mental retardation
  • Children typically reach a maximum developmental age of 18 months in language and fine motor function.
  • Receptive language abilities are better than expressive abilities
  • Hypotonia (low muscle tone), but tendon reflexes are usually spastic
  • Corneal clouding
  • Pseudo-strabismus (false appearance of crossed eyes)
  • Progressive retinal degeneration, resulting in blindness by late teenage years
  • MRI of the brain typically shows a thin corpus collosum, and delayed growth in white matter of brain (myelination)
  • Achlorhydria (lack of acid in the stomach)
  • Elevated gastrin levels in stomach
  • Anemia (iron deficiency)
  • Individuals with ML4 typically survive to early adulthood.

Atypical and Mild Mucolipidosis Type IV (ML4)

  • Individuals with Atypical or Mild ML4 are less severely affected than others with Typical “Classic” ML4
  • Some individuals attain the ability to walk independently. They develop slowly progressive ataxia and may have mild eye abnormalities
  • Other individuals have presented with progressive visual impairment while having relatively normal psychomotor development

DIAGNOSIS

  • Individuals with clinical findings (symptoms) for ML4 can have a simple blood test to check for elevated gastrin levels.
  • Molecular genetic testing will confirm the diagnosis in most individuals.
  • Two mutations of the gene account for 90% of mutations in individuals of Ashkenazi (Eastern European) heritage.

TREATMENT

  • There is no medical treatment available at the present time.
  • Intensive physical therapy for spasticity and ataxia is highly recommended for acquisition of speech, feeding, and motor skills, and prevention of secondary complications such as tightened ligaments and difficulties with balance.
  • Some individuals may develop the ability to sit independently or crawl. Many have learned to walk with the aid of ankle-foot orthotics (AFO’s) and gait trainers.
  • Occupational, speech, and vision therapies are also highly recommended to improve life skills.
  • Spoken language is limited to a few or no words. Many individuals use some sign language to communicate.
  • Some children have had success with the use of “auditory scanning” to make choices.
  • Iron supplements are important to prevent anemia.
  • Pureed foods and thickened liquids are necessary for many individuals, to prevent choking and aspirating while eating.