Rapid-onset Obesity The rapid onset obesity aspect of<unk>  is usually the first diagnostic indicator of the disease. Patients often present with hyperphagia and rapid weight gain. This rapid weight gain is defined as 20-30 pounds over a 6-12 month period, and typically occurs between the ages of 1.5 and 11. Hypothalamic dysfunction Hypothalamic dysfunction refers to the hypothalamus, which is a structure within the brain which participates in regulating the pituitary gland, autonomic nervous system, and endocrine system. Symptoms related to hypothalamic dysfunction may include abnormal sodium balance (hyponatremia or hypernatremia), high progestin levels, low cortisol levels, delayed or early-onset puberty, and low thyroid hormone. Patients will also often experience a decelerated growth rate throughout childhood. Sodium imbalance within the body can have severe symptoms and be potentially life-threatening if not controlled. Hyponatremia, or low sodium levels, can cause symptoms such as nausea, headache, seizures, or even cause patients to become comatose. Hypernatremia, or high sodium levels in the blood, can cause nausea, muscle weakness, altered mental status, or coma. Irregular temperature regulation and diabetes insipidus are also possible symptoms of hypothalamic dysfunction.<unk>  patients develop these symptoms at varying ages and in varying numbers, but all patients will develop some symptoms of hypothalamic dysfunction. Hypoventilation Symptoms of hypoventilation and breathing malfunctions typically present after the rapid weight gain. Some patients may initially develop obstructive sleep apnea, which is common in obese children. Obstructive sleep apnea is the most common form of sleep apnea, and causes breathing to abruptly stop and begin again during sleep. This is caused by throat muscles relaxing during sleep and blocking the airway, and is typically noticed as patients will snore loudly throughout the night. Every patient diagnosed with<unk>  develops alveolar hypoventilation, regardless of whether they presented with sleep apnea. Alveolar hypoventilation is a condition in which patients have very low blood oxygen levels and shallow breathing. In healthy patients, when blood oxygen levels are low, the brain sends a signal to breathe and bring more oxygen to the blood. In<unk>  patients, this reaction does not occur. This condition is usually only present during sleep, however in more severely affected patients shallow breathing may continue throughout the day. Hypoventilation can go unnoticed until cardiopulmonary arrest, which is why<unk>  has the potential to be a fatal disease. Ventilatory support is required for patients during sleep, however it is only needed during waking hours for those most severely affected (about 50% of patients). Autonomic Dysfunction Autonomic dysfunction refers to the autonomic nervous system, which is responsible for regulating internal processes without conscious intervention. This may involve abnormalities in cardiac rhythm, temperature regulation, digestion, and eye movements. Not all<unk>  patients will experience all of these symptoms, however they will have at least some of these issues. Examples of autonomic dysfunction include hyperthermia, hypothermia, pupillary dysfunction, strabismus, chronic constipation, and chronic diarrhea. Neuroendocrine tumors Approximately 40% of<unk>  patients will develop tumors originating in the neural crest. These tumors are typically classified as ganglioneuroma or ganglioneuroblastomas. These tumors are not believed to significantly worsen or contribute to the prognosis of<unk> . It was suggested that<unk>  be renamed<unk> NET in order to include these tumors in the diagnostic criteria, but this has only been adopted for patients who develop these tumors. Behavioral issues Some children diagnosed with<unk>  may also present with behavioral disorders and/or intellectual disability, however this is believed to be a result of low oxygen levels secondary to hypoventilation during childhood development. The later<unk>  is diagnosed, the greater the risk for behavioral problems due to hypoxia from hypoventilation or during cardiopulmonary arrest.
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