An entity including gelastic epilepsy, precocious puberty, polydactyly and a hypothalamic hamartoma type IIa is described in a 16-year-old female patient. Polydactyly was detected at birth, she developed precocious puberty at four years of age, and gelastic epilepsy was diagnosed at age seven. The precocious puberty was successfully treated medically and her treatment was discontinued at the age of 10 years, but the gelastic seizures were difficult to control. When the patient was 11 years old, MRI revealed a hypothalamic hamartoma. The combination of these four features is very rare in the literature.