The onset of Krabbe disease usually occurs between the ages of three to six months. Features include irritability, choking, loss of developmental and motor skills, myoclonic and general seizures (see entry Epilepsy), blindness, spasticity (stiffness of the limbs), paralysis and weight loss; unexplained fevers are noted in the last phases.
There are three stages of the condition:
- stage I - general irritability, stiffness, arrest of motor and mental development and episodes of high temperature without the presence of an infection
- stage II - infants may have severe arching of the back and have myoclonic-like jerks of the arms and legs, hypertonic fits, bouts of fever and loss of learned skills
- stage III - infants are severely impaired with no voluntary movement.
The average age of death is between 13 months to 2 years, although infections and respiratory failure may bring about an earlier death.
Besides this most frequent infantile form, there are also juvenile and adult forms of Krabbe disease. These variants become apparent later, progress more slowly and those affected may live well into middle age - with perhaps only leg stiffness and sometimes painful nerve roots.