In most cases, inherited metabolic diseases in children are lifelong conditions that require lifelong treatment. While some have effective therapies and successful outcomes, there are others that are very difficult to treat. Without effective treatment, these diseases can lead to developmental problems, neurological complications, neuro-developmental problems and failure to grow. Treatment may involve something as simple as changes in the diet, medications and a dietary supplement, or a combination of therapeutic approaches. For example, infants with PKU can be placed on a specialized diet that will prevent the mental retardation that would otherwise occur.