Given a question and a context passage, generate the answer having the word or phrase from the context passage. Here, the answer should be a shortest continous span from the passage.

Context: Mutations of SLC9A6 may cause an X-linked clinical syndrome first described by Christianson in 1999 in which affected males exhibited profound intellectual disability, autism, drug-resistant epilepsy, ophthalmoplegia, mild craniofacial dysmorphism, microcephaly, and ataxia. We describe a child with an SLC9A6 mutation and an electroencephalographic pattern consistent with electrographic status epilepticus of sleep. Our patient's electrographic status epilepticus of sleep resolved after treatment with felbamate. Following treatment, he remained seizure-free but did not make significant or lasting gains in language. Our report extends the clinical epilepsy phenotype in children with SLC9A6 mutations to include electrographic status epilepticus of sleep. In addition, felbamate was an effective treatment for electrographic status epilepticus of sleep in our patient. 
 Question: Mutation of which gene is implicated in the Christianson syndrome?
slc9a6

Context: In the county, the population was spread out with 23.20% under the age of 18, 7.70% from 18 to 24, 27.00% from 25 to 44, 28.00% from 45 to 64, and 14.10% who were 65 years of age or older. The median age was 40 years. For every 100 females, there were 97.00 males. For every 100 females age 18 and over, there were 96.40 males. 
 Question: Which age group had the least people?
18 to 24

Context: The authors reported a 73-year-old alcoholic man with previously-unrecognized situs inversus totalis suffering from left upper quadrant pain. Acute myocardial infarction was diagnosed and coronary angioplasty was performed immediately. However, the massive bleeding from the previously-unfound hepatomas caused hypovolemic shock and fatal outcome. Situs inversus totalis is a rare congenital anomaly with a complete mirror image of the thoracic and abdominal organs. Although being considered a benign entity, it would disturb diagnosis-making of the visceral diseases owing to the altered anatomy. To our knowledge, the coexistence of the coronary artery disease and ruptured hepatomas in situs inversus totalis, as in our patient, is never described. Recognition of any situs anomalies in time is the key to avoid misdiagnosis, inappropriate managements, and unwanted consequences. 
 Question: What is situs inversus?

situs inversus totalis is a rare congenital anomaly with a complete mirror image of the thoracic and abdominal organs.