However, some acquired causes, such as alcoholic cirrhosis, show a population distribution skewed by societal phenomena. Genetic causes manifest themselves under a wide variety of conditions. The different presentations are categorized as catastrophic newborn, late-infantile, and adult. Each inherited disorder is reported in various clinical presentations. In some adult-onset patients, no precedent sign of intellectual dysfunction was present, leading to the assumption that the disorder was truly latent until the first acute presentation.
Age of onset depends upon the age and rate of progression of the underlying disease process.
Impairments that must be considered range from hepatic necrosis with hepatocellular damage to inborn genetic disorders of the urea cycle. While history and age of the patient are helpful to diagnosis, genetic causes must never be disregarded, irrespective of the stage of life. The multiple primary causes of hyperammonemia, specifically those due to urea cycle enzyme deficiencies, are somewhat variable in presentation, diagnostic features, and treatment. For these reasons, the family of urea cycle defects is considered individually in this textbook. As a consequence, the most striking clinical findings of each individual urea cycle disorder relate to this constellation and roughly temporal sequence of events.