*2.3.2 Clinical features*

The clinical manifestation of HP2 is variable [114] and asymptomatic cases have been described [115]. Seizures are the most common clinical fining in HP2 which occur in about 50% of the cases [6, 114]. They are often triggered by febrile illness and have variable age of onset; commonly occurring during infancy or childhood but can also be up to late adulthood (63 years in one HP2 case [116]) [6, 114, 117, 118]. Intellectual and neuropsychiatric abnormalities have also been described in some HP2 patients. In the original HP2 Irish traveler family, 9 out of the 13 affected individuals developed seizures and two of them had intellectual disability [118]. Van de Ven [119] reported 5 HP2 patients; all presented with seizures, 3 had intellectual disability and 4 suffered behavioral problems.
