Differential diagnosis of common forms of arthritis
Richard Travers
Senior Rheumatologist and Head of Rheumatology Unit
Western Hospital, Footscray, Australia
This brief talk is aimed at the general physician whose opinion has been sought about a patient with joint pains. Rheumatology is a clinical specialty. There are a limited number of ways that a joint can react to noxious stimuli, and the answers to questions generated by the history and physical examination will nearly always point you in the right direction, and examples of the common entities will be given. The exceptions are those rare periodic syndromes (palindromic rheumatism and FMF, for example) where the joints and back movements may look normal at the first visit. The joints will also look normal in the common, but distressing, fibromyalgia, in some viral syndromes and in statin-related myalgia.
The history gives you the pathology, and the examination gives you the anatomy. The first decisions relate to acute
versus chronic, degenerative versus inflammatory (and if so, idiopathic, infective, or crystal-induced), and the pattern of joint involvement (remembering that symmetrical arthritis may be quite asymmetrical in degree). The presence of associated features needs to be systematically asked for, such as hair fall, rash (psoriatic, vasculitic,viral), eye involvement (iritis, steroid effects), bowel or urinary tract inflammation. The family history is often surprisingly unhelpful, partly because patients seem unclear as to the rheumatic diagnoses of family members. If there is a family history of rheumatoid arthritis or SLE, it is important to reassure the patient that things are better
these days, even if that is the diagnosis in their case.
The physical examination confirms the pattern of joint involvement, which is usually characteristic. It also may disclose obvious features such as primary osteoarthritis of the hands, gouty tophi, marked synovitis, psoriasis or vasculitis. The examination of the urine sediment for cells and casts should be routine, because glomerulonephritis isthe only rheumatic feature which doesn’t cause symptoms. Sometimes the diagnosis isn’t clear, but this in itself should be reassuring. No one gets it right all the time, and the uncertainty emphasizes the need for good communication.
Radiological investigation is helpful, with characteristic patterns of degenerative change, osteopenia or erosive change in the common arthritides. With the spine, circumspection is required, because the age-related changes displayed may not correlate with the clinical findings. Nothing beats an absent ankle or biceps jerk for significance. Common blood tests, such as those for rheumatoid factor, anti-nuclear antibody and serum urate level, are extremely
useful, but only after you have already got it clear in your own mind, from evidence gained via the history and examination, what the diagnosis is likely to be. Otherwise, a laboratory test result might steer you off course.
Raynaud’s phenomenon – is this patient’s ANA significant? Does this patient simply have osteoarthritis plus hyperuricaemia? Does this elderly patient have rotator cuff problems and OA hips, or does she have polymyalgia rheumatica? Is the chronic synovitis at the left wrist caused by seronegative arthritis or TB (the old name for which was “white swelling”)? Your clinical impression from the history and examination will help you answer these difficult questions.