Congenital analbuminaemia (CAA) is a very rare condition manifested by the near complete absence of albumin, the major blood protein, because of defects in the albumin (ALB) gene. It is generally regarded as relatively benign in adults, but analbuminaemic individuals may be at risk during the perinatal and childhood period. Twenty-one different molecular lesions in the ALB are now known as cause of the trait. These include one mutation in the start codon, one frameshift/insertion, five frameshift/deletions, seven nonsense mutations and seven mutations affecting splicing. Thus, nonsense mutations, mutations affecting splicing and frameshift/deletions seem to be the most common causes of CAA. These results indicate that the trait is an allelic heterogeneous disorder caused by homozygous or, in a single case, compound heterozygous inheritance of defects. Most mutations are unique, but one, named Kayseri, is responsible for about half of the known cases.