MLD is short for Metachromatic Leukodystrophy. People who are affected by MLD lack an enzyme in there blood Arylsufatase-A (ARSA). Without this enzyme, sulfatides are NOT broken down and build up in the white matter of the brain and CNS causing destruction of the myelin sheath. Without an intact myeline sheath there is a breakdown in communication between the nerves and the brain. This loss or miscommunication account for the loss of acquired function, paralysis, blindness, seizures and eventual death.
Generally, there are considered to be three main types of MLD that has different ages of onset:
late-infantile...(this is what Tannis had)
MLD is NOT contagious and can not be passed on to other through any sort of contact - it is a genetic condition
To learn more http://mldfoundation.org