Within the first few months, or even weeks, of  life the baby will feed poorly, tend to vomit, lose weight and be excessively unsettled. From about the age of 5 months, milestones will not be achieved and, indeed, skills that have been learnt will slowly be lost again. The baby will also adopt a stiff posture and may startle very easily. The optic nerve in the brain will be affected so that vision will deteriorate and be lost over time and there may be  episodes of unexplained fever. The condition itself is not painful and, obviously, the baby will be unaware of what is happening, though the effects of some of the physical problems ( ie the stiffness and startles) are likely to be upsetting and will require treatment. The brain’s control of muscles responsible for chewing, coughing swallowing etc. eventually becomes affected so that assistance with a feeding tube may be needed, and chestiness will develop which may lead to infections and increasing physical weakness. Eventually the combination of the diseased brain and physical weakness becomes too great to sustain life, and death usually occurs between the ages of 9 months and 3 years. Parents and carers will be aware of the child’s increasing frailty, and death is usually relatively peaceful and expected when the time comes.