text: Etiology
  Anorectal malformations (ARM) represent a spectrum of abnormalities ranging from mild anal anomalies to complex cloacal malformations. The etiology of such malformations remains unclear and is likely multifactorial. There are however reasons to believe there is a genetic componenet. As early as the 1950s, it was recognized that there was an increased risk for a sibling of a patient with ARM to be born with a malformation, as much as 1 in 100, compared with the incidence of about 1 in 5000 in the general population. Since that time there have been reports of families with 2 or more affected members and associations of ARMs with multisystem syndromes. In particular, mutations in specific genes encoding transcription factors have been described in patients having Townes-Broks syndrome, Currarino's syndrome, and Pallister-Hall syndrome, each of which have autosomal dominant modes of inheritance. In addition, it has been found that there is not only an increased incidence of ARM in patient with trisomy 21 (Down's syndrome), but that 95% of patients with trisomy 21 and ARM have imperforate anus without fistula, compared with only 5% of all patients with ARM. Based on this evidence, it is likely that the mutation of a variety of different genes can result in ARM, or that the etiology of ARM is multigenic [13].
  
entities.text: ['Anorectal']
entities.type: Organism_subdivision
entities.entity_id: PMC-1971061-sec-09_T1
entities.text: ['anal']
entities.type: Immaterial_anatomical_entity
entities.entity_id: PMC-1971061-sec-09_T2
entities.text: ['anus']
entities.type: Immaterial_anatomical_entity
entities.entity_id: PMC-1971061-sec-09_T3
entities.text: ['fistula']
entities.type: Pathological_formation
entities.entity_id: PMC-1971061-sec-09_T4