INTRODUCTION

New-onset psychosis in children and adolescents represents an uncommon and complex presenting complaint. Psychosis has been defined as a "disruption in thinking, accompanied by delusions or hallucinations" [1]. Delusions represent false, fixed beliefs that cannot be resolved through logical argument, while hallucinations are false perceptions that have no basis in external stimuli [1]. In contrast, delirium is marked by an altered sensorium with waxing and waning deficits in attention and concentration. Orientation and concentration are preserved with functional psychosis. However, the distinction between delirium and psychosis in pediatric patients can be difficult to establish, particularly in younger children. Despite these differences, hallucinations may actually represent a symptom of delirium, and separating psychosis and delirium acutely may be impossible.

The onset of psychosis is an important diagnostic element. Acute onset occurs more commonly with an underlying medical cause rather than psychiatric disease. Even patients with symptoms suggestive of a primary psychiatric diagnosis should undergo a medical evaluation to exclude possible reversible etiologies of psychosis.

DIFFERENTIAL DIAGNOSIS

The differential diagnosis of psychosis in children encompasses hypoglycemia, cerebral hypoxia, drug toxicity, medical illness, and psychiatric disease (table 1 and table 2).

Substrate deficiency

• Hypoglycemia – Hypoglycemia is a rare, but important cause of psychosis and hallucinations [2,3]. All patients with alterations in mental status require immediate bedside capillary glucose testing. Rapid correction of blood sugar is critical to prevent seizures and persistent neurologic sequelae. Hypoglycemia with abrupt change in behavior may occur in children being treated for Type I and Type II diabetes; alternatively, hypoglycemia may result from ingestions (eg, ethanol, beta-blockers, and sulfonylureas) or from inborn errors of metabolism. (See "Approach to hypoglycemia in infants and children".)
• Cerebral hypoxia – Inadequate brain oxygenation may lead to altered mental status with combative behavior. Thus, any condition that results in hypoxemia (eg, pulmonary insufficiency), insufficient oxygen carrying capacity of the blood (eg, severe anemia), or inadequate brain perfusion (eg, cardiac insufficiency) may result in an encephalopathy with psychotic features. These patients require emergent identification of the underlying cause of cerebral hypoxia and immediate interventions to restore brain oxygenation.

Drug toxicity — Drug exposures are a common cause of delirium, delusions, and/or psychosis, especially in the adolescent population.