Neurological and Psychiatric Symptoms

Late-onset forms of inborn errors of metabolism (IEM) first presenting in adulthood often display psychiatric or neurological manifestations, including atypical psychosis or depression, unexplained coma, peripheral neuropathy, cerebellar ataxia, spastic paraparesis, dementia, movement disorders, or epilepsy. With the exception of several review articles, most if not all existing books and diagnostic algorithms refer to pediatric forms of these diseases. Late-onset forms of IEM always display attenuated phenotypes, which in some instances are associated with one or more clinical manifestations that differ from the classic clinical picture described in children. Although the limited information available about adult forms of IEM makes the specialty new and quite exploratory, the diagnostic approach in adults is facilitated by the fact that the nervous system is already mature. Therefore, clinical presentations are more homogeneous than in children, in whom clinical signs usually differ depending on their stage of maturation.