Reactive (spondylo)ahritis (ReA) is a 'reaction' to a number of bacterial triggers with clinical features in keeping with all SpA conditions. The known triggers are Chlamydia, Campylobacter, Salmonella, Shigella and Yersinia. Notably, non-SpA-related reactive ahritis can occur following infection with many viruses, Mycoplasma, Borrelia, streptococci and mycobacteria, including M. leprae, which causes leprosy (Hansen's disease); however, the 'reaction' in these instances consists typically of myoahralgias, is not associated with HLA-B27 and is generally not chronic. The ahritis associated with rheumatic fever is also an example of a reactive ahritis that is not associated with HLA-B27.Sexually acquired reactive ahritis (SARA) is predominantly a disease of young men, with a malepreponderance of 15 : 1. This may reflect a difficulty in diagnosing the condition in young women, in whom Chlamydia infection is often asymptomatic and is hard to detect in practical terms. Between 1% and 2% of patients with non-specific urethritis seen at genitourinary medicine clinics have SARA. The syndrome of chlamydial urethritis, conjunctivitis and reactive ahritis was formerly known as Reiter's disease. Clinical features The onset is typically acute, with an inflammatory enthesitis, oligoahritis and/or spinal inflammation. Lower limb joints and entheses are predominantly affected. In all types of ReA, there may be considerable systemic disturbance, with fever and weight loss. Achilles inseional enthesitis/tendonitis or plantar fasciitis may also be present. The first attack of ahritis is usually self-limiting, but recurrent or chronic ahritis can develop and about 10% still have active disease 20 years after the initial presentation. Low back pain and stiffness due to enthesitis and osteitis are common and 15-20% of patients develop sacroiliitis. Many extra-aicular features in ReA involve the skin, especially in SARA: * circinate balanitis, which stas as vesicles on the coronal margin of the prepuce and glans penis, later rupturing to form superficial erosions with minimal surrounding erythema, some coalescing to give a circular pattern * keratoderma blennorrhagica, which begins as discrete waxy, yellow-brown vesico-papules with desquamating margins, occasionally coalescing to form large crusty plaques on the palms and soles of the feet * pustular psoriasis * nail dystrophy with subungual hyperkeratosis * mouth ulcers * conjunctivitis * uveitis, which is rare with the first attack but arises in 30% of patients with recurring or chronic ahritis. Other complications in ReA are very rare but include aoic incompetence, conduction defects, pleuro-pericarditis, peripheral neuropathy, seizures and meningoencephalitis . Ref - Davidsons 23e p1031