Total absence of the 2(I) chain of collagen type I causes a rare form of Ehlers-Danlos syndrome with hypermobility and propensity to cardiac valvular problems

Heterozygous mutations in the COL1A1 or COL1A2 gene encoding the alpha1 and alpha2 chain of type I collagen generally cause either osteogenesis imperfecta or the arthrochalasis form of Ehlers-Danlos syndrome (EDS). Homozygous or compound heterozygous COL1A2 mutations resulting in complete deficiency of the proalpha2(I) collagen chains are extremely rare and have been reported in only a few patients, albeit with variable phenotypic outcome.The...