The absence or dramatic reduction of circulating human serum albumin (HSA) with less than 50 cases reported in the literature so far. In the majority of cases the disorder is diagnosed in adulthood. Although albumin is the most abundant plasma protein and has many functions, patients present with only a few mild clinical signs and biochemical abnormalities, HSA is either absent or present at very low levels (<1 g/L) but liver function is normal and there is an absence of conditions leading to significant protein loss. The disorder appears to be more severe in the fetus or during early infancy. Transmitted as an autosomal recessive trait and consanguinity has been shown in all reported cases, the disorder is caused by homozygous or compound heterozygous mutations in the gene coding for HSA (ALB; 4q13.3).