ASLD is divided into three categories based on the severity of symptoms: the fatal neonatal form, type I and type II. However, as symptoms occur along a spectrum there are no set criteria to determine which category a patient should be ascribed to. Fatal neonatal form Patients with this form of ASLD present with fatal neonatal encephalopathy, respiratory failure, a lack of spontaneous movement and intractable seizures. Possible prenatal symptoms such as microcephaly, intrauterine growth restriction, loss of fetal heart rate variability and hypokinesia have been reported. Death occurs within the first few weeks of life. Type I This is the most common form of ASLD. Symptoms become apparent in the first months of life and include seizures, microcephaly and severe psychomotor retardation are purely neurological. Some patients display axial hypotonia, peripheral hypertonia and normal tendon reflexes. Autistic-Like behaviour including poor eye contact, stereotypies, agitation, tantrums and self injurious behaviour may occur. Type II This is considered to be a mild to moderate form of ASLD. They may demonstrate a milder degree of psychomotor retardation and transient visual and auditory contact disturbances Seizures, if they occur, begin later than in Type I, typically between 2 and 4 years old but sometimes as late as 9 years old. Speech is impaired with receptive language skills and nonverbal communication skills being better that expressive language skills. Ataxia may occur and cause increasingly severe gait disturbances.
Adenylosuccinate lyase deficiency
Guanidinoacetate methyltransferase deficiency
Malonyl-CoA decarboxylase deficiency
Mevalonate kinase deficiency
Aminoacylase 1 deficiency
Carbamoyl phosphate synthetase I deficiency
2,4 Dienoyl-CoA reductase deficiency
Galactose-1-phosphate uridylyltransferase deficiency