Spondyloarthropathies

Question 1

What is spondyloarthritis

Answer 1

This is a group of conditions affecting the spine and peripheral joints which cluster in families and are linked to certain type 1 HLA antigens

Question 2

What is the etiology of spondyloarthritis

Answer 2

The common aetiological thread of these disorders is their striking association with HLA-B27, particularly ankylos-ing spondylitis (AS). HLA type B27 is present in >90% of Caucasians with AS but only 8% of controls. HLA-B27 exhibits a number of unusual characteristics including a high tendency to mis-fold but its aetiological relevance remains unclear. The role of class I HLA antigens in pathogenesis is supported by the fact that HLA-B27 transgenic mice spontaneously develop arthritis, skin, gut and genitourinary lesions.
There are clues that infections play a role, possibly by molecular mimicry, with parts of the organism which are structurally similar to the HLA molecule triggering cross-reactive antibody formation. This is unproven. AIDS is increasing the prevalence of reactive arthritis and spondylitis in sub-Saharan Africa even in the absence of HLA-B27. The explanation for this changing epidemiology is unclear.
The types of arthritis that follow a precipitating infection are called reactive arthritis (p. 529).
The specialized immune systems of the gut and genitouri-nary mucous membranes may also play a causal role,

Question 3

What is alkalosing spondylitis

Answer 3

This is an inflammatory disorder of the spine affecting mainly young adults (late teens to early 30s). It occurs worldwide, with a male to female ratio of 5:1. Women present later and are underdiagnosed.