The term heterotaxy is used for patients with isolated situs inversus of various degrees; heart defects and other organ malformations such as asplenia or polysplenia are also often observed. Heterotaxy has been associated with pathogenic variants in several genes, including ACVR2B, CFC1, CRELD1, GDF1, LEFTY2, NODAL and ZIC3. However, these can only explain about 10‑20% of heterotaxy cases and the underlying cause remains unknown in the majority of patients. In most cases, inheritance is autosomal dominant; autosomal recessive and also X‑linked inheritance are described less often. Due to the phenotypic overlap it is assumed that some patients with the clinical diagnosis of heterotaxy may also have Kartagener syndrome, which belongs to the group of primary ciliary dyskinesias.
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