In general terms there are two types of presentation in AGS. Some babies, especially those with AGS1 mutations (see 'What are the causes?'), experience problems at or very soon after birth. Features include feeding difficulties, abnormal neurological signs, low platelets (blood cells involved in clotting), and liver abnormalities. In contrast, other children, most frequently those with AGS2 mutations, develop normally for the first few weeks or months of life. They then experience the sudden onset of a period of intense irritability, cry a lot for hours at a time, sleep poorly, and can develop fevers without infection. During this period there is a loss of skills.
After a few months the disease process seems to 'stop'. Many individuals with AGS are still stable in their late teens and early twenties. Typical neurological features of AGS include learning problems, stiffness of the limbs with poor body and head control, dystonia (impairment in muscle tone) of the limbs, and seizures (see entry Epilepsy). Although the neurological problems seen in AGS are often severe, a small number of children, usually those with AGS2 or AGS5-7 mutations, display good communication skills, and a few children can have completely normal intellectual development.