The systemically ill patient

Diagnosis of the systemically unwell patient is a very common rheumatological problem. The patient may present with seemingly disparate problems in different organ systems; the challenge is to identify whether there is a unifying underlying disease process, such as infection, malignancy, an autoimmune inflammatory condition, or an autoinflammatory disease, or if different disease processes are coincidentally occurring within the same patient. A systematic approach requires a thorough history, examination, and appropriate baseline investigations, before the use of potentially more invasive and specialist tests—because common things are common. With practice, the diagnostic process should also be one of pattern recognition; examining each feature and asking: does this fit—or is there something we are missing? This caution to ensure the correct diagnosis before starting treatment is appropriate; for example, gaining biopsy evidence of systemic vasculitis before starting therapy with steroids or immunosuppressants is important, to avoid inappropriate treatment which may mask or worsen an underlying condition such as tuberculosis or lymphoma. In individual cases, though, delays brought about through waiting for further investigations to conclusively prove the diagnosis, will be less acceptable in the case of a patient with rapidly worsening organ or life-threatening disease. In this chapter we propose a stepwise approach to the systemically unwell patient.