Panic disorder is defined in the 'Diagnostic and Statistical manual of mental disorders- 5th edition' (DSM-V) criteria as the recurrent occurrence of sudden onset disabling intense fear accompanied by somatic symptoms. It is one of the commonest psychiatric conditions and adversely affects the quality of life with economic consequences. Diagnosis of the condition is based on the exclusion of more serious illnesses like myocardial infarction and angina which can present with similar symptoms.
The DSM-V  defines panic disorder (PD) as the recurrent onset of sudden fear accompanied by somatic symptoms like palpitations, excessive sweating, and dyspnea. Other criteria include persistent anxiety about recurrence and its consequences or inappropriate behavioral changes. In order to diagnose PD, it is important to exclude medical illnesses, substance abuse, and other psychiatric disorders as the cause of the panic attacks.
The clinical presentation of panic attacks and PD can mimic the symptoms of coronary heart disease  and cardiomyopathies , making it difficult to differentiate between the conditions clinically . For example, symptoms like chest pain, palpitations, sweating, discomfort, and dyspnea are common to PD as well as myocardial infarction (MI), angina pectoris and pulmonary embolism. Other somatic symptoms of PD include cold clammy hands, headache, diarrhea, insomnia, weakness, intrusive thoughts, and ruminations. The attacks in PD are often related to certain places or situations. Patients develop anxiety about the recurrence of the attack and start avoiding these situations and places resulting in agoraphobia . This can further lead to the development of safety behaviors like dependence on anxiolytic medications and avoiding being alone .
Although no gender differences have been observed in the expression of PD symptoms in children and adolescents, a higher incidence of PD has been observed amongst girls. Children and adolescents experience somatic symptoms similar to those seen in adults and these include palpitations, dyspnea, sweating, chest pain, nausea, abdominal discomfort, dizziness, restlessness and a sense of losing control   .
Diagnosis of PD can be challenging as its clinical presentation resembles that of several serious acute conditions. Therefore the diagnosis is often based on the exclusion. History, physical examination and mental status examination are the pillars of PD diagnosis. An electrocardiography (ECG) should be obtained early during the workup to rule out myocardial ischemia and conduction abnormalities in all patients presenting with palpitations, chest pain, dyspnea, and sweating. Pulse oximetry will usually show either normal or slightly higher oxygen levels. Arterial blood gas analysis is performed to exclude metabolic acidosis and hypoxemia. In patients with a history of a syncopal event, ambulatory Holter monitoring should be considered. A D-dimer test, spiral computed tomography (CT scan), lower limb Doppler or ventilation-perfusion (V/Q) scanning is indicated to exclude pulmonary embolism especially in those at risk. Electroencephalography may be required to differentiate PD from partial complex seizures.
Laboratory studies should be performed to exclude substance abuse and other medical conditions. These include complete blood count, hemoglobin, urine toxicology, serum electrolytes, serum glucose, cardiac enzymes and, thyroid-stimulating hormone.
Orexin or hypocretin has been shown to play a role in the pathogenesis of panic in rats  and elevated levels have been observed in the cerebrospinal fluid of individuals with panic attacks.
Functional magnetic resonance imaging is not routinely recommended in the workup of PD although increased flow in the right parahippocampal region with decreased serotonin type 1A receptor binding in the anterior and posterior cingulate and raphe of patients with panic disorder has been noticed on positron emission tomography (PET) scanning . Patients with PD have also been observed to have smaller temporal lobe volume on magnetic resonance imaging .