International Hypothalamic Hamartoma Awareness Day Date in the current year: September 15, 2025

A hamartoma is a type of benign tumor composed of an abnormal mixture of normal tissues and cells native to the organ in which it develops. A hypothalamic hamartoma (HH) is located in or near the hypothalamus, which is a small region of the brain that connects the nervous and endocrine systems. HHs arise during embryonic development and are present at birth. Hypothalamic hamartomas are very rare, affecting about one in 200,000 people.

The hypothalamus is an important part of the brain that regulates hunger, thirst, sleep, body temperature, and circadian rhythms. It also plays a role in certain social behaviors, such as aggressive and sexual behaviors, as well as the mother-child bonding process. Since the hypothalamus is so important, HHs can cause serious issues despite being benign.

Gelastic seizures, also known as laughing seizures, are an early sign of a hypothalamic hamartoma. A gelastic seizure is an abrupt, unprovoked outburst of laughter that occurs without the experience of joy. A person having a gelastic seizure may appear startled or even panicked. These seizures may last only a few seconds, but they can occur many times a day, sometimes several times per hour.

A child with a hypothalamic hamartoma may begin experiencing gelastic seizures before their first birthday. These seizures usually become less frequent by age ten, though patients may develop other types of seizures, such as atonic (drop attacks) or tonic-clonic seizures.

Since the hypothalamus controls the release of certain hormones, including sex hormones, a hypothalamic hamartoma can also cause precocious puberty (before age eight in girls and before age nine in boys). The tumor may also affect cognitive function, behavior, and mood, causing neurological symptoms and comorbidities such as attention deficit/hyperactivity disorder (ADHD), conduct disorder, mood disorders, oppositional defiant disorder, reactive behavior (anger and aggression), short-term memory problems, and intellectual disability.

Hypothalamic hamartomas can be treated surgically, especially when they cause drug-resistant gelastic seizures or severe endocrine and behavioral problems. Other treatment options include anti-seizure medications (which are usually ineffective for gelastic seizures but may help with other seizure types), gonadotropin-releasing hormone agonists for precocious puberty, therapy and/or medications for mood and behavioral disorders, and educational support in school.

International Hypothalamic Hamartoma Awareness Day is celebrated on September 15 during International HH Awareness Month. The day’s main goals are to educate the public about hypothalamic hamartomas, support those diagnosed with HH and their families, and further research into the condition and its treatment.