Fewer than 1 in 100,000 newborn babies have type 2 disease and this form of the disease is not associated within any particular ethnic group.
Babies usually appear normal at birth but develop neurological and other symptoms by the age of 3-6 months. Type 2 is almost always apparent by 6 months of age. Many children die in infancy and survival beyond 2 years is rare.
In some exceptional cases, the disease course may be prolonged over a number of years.
Early signs and symptoms include slow development, squint (strabismus), poor feeding and slow weight gain. In the subsequent months, developmental milestones may be lost (regression), there may be rigidity of the neck and limbs (hypertonia), back arching, abnormal head postering, and noisy breathing (stridor), swallowing problems and recurrent vomiting may become apparent. The abdomen may appear very swollen due to enlargement of the liver and spleen.
As the disease progresses, other difficulties such as throat (laryngeal) spasm, seizures, low blood counts, bleeding and a failure to shake off colds and other infections may complicate the course. The lungs may also be affected and the bones may show signs of disease.
In later stages of the disease the infant may show signs of pain and distress that may arise from spasms, seizures, choking, breathing difficulites, infections, bleeding and bone pain. It is very important to recognise and manage these symptoms with appropriate measures and pain relief in order to keep the child as comfortable as possible.
Sudden death may occur or in some cases the baby may eventually switch off, not reacting to parents or stimulus for a period before death. It is important for families to seek palliative care for their child to ensure the child is as comfortable as possible and to support those caring for the child.