Patients with Ancylosing Spondylitis (Morbus Bechterew = M. B.) have cell surface molecules of the HLA-B27 group in 90 % of the cases, whereas the normal abundancy is only up to 10 % positives. Absence of HLA-B27 alleles in a person can therefore diminish the probability of a M. B. diagnosis in the internistically demanding diagnosis of spondylarthropathies (especially in young people). Additionally segregation between certain "disease coupled" B27- types has been worked out by the modern molecular medical research (actually there are now 45 human HLA-B27 alleles known differing in amino acid changes in their protein sequence – an “update” for MutaGEL® HLA B27 is done periodically). Of epidemiological relevance are only the alleles *2701 - *2710; all other HLAB27 types are described in single cases only.
That means, only some of the HLA-B27 allele types are abundant: Types *2701, -02, -04, -05, -07, -08 and -10 are associated with the chronic inflammatory rheumatic disease M. B. and population studies for them are available. The types *2706, -09, -12 and -18 are not associated with M. B., most of the others having been reported only once. This variability characterizes the frame of the diagnostic demand, keeping in mind the possibility of occurrence of further new sequence findings.