Clinical Case 062: Vasculitis – making rash decisions?
August 4, 2012
This case is a bit backwards, as are a lot of things in medicine.
I am going to show you a picture – tell you what it is and then ask you to tell me where to next? 35 year old mother of 4 kids comes to see you with this rash.
Here is the image: OK, this is a symmetrical lower limb, palpable purpura. The RMO has already done a batch of tests looking for coagulopathy, thrombocytopenia, sepsis etc…. they are all plum normal other than a mildly raised CRP and ESR.
This is vasculitis, it looks and feels like vasculitis. The patient is otherwise well aside from an associated mild effusion of the left ankle which is mildly tender but not hot.
So here is the starting point – the patient looks like they have developed a new vasculitis. This could be due to a whole range of diseases. So now in order to make a diagnosis, look smart and help this patient what do you need to know next?
The diagnosis is always on the history (90% anyway)! Think of he causes of vasculitis and ask about their triggers and associated features. Infections: sepsis, viral – Hep B, are usually easy to pick – ask about fever, constitutional sxs, recent respiratory or gut symptoms. However, this patient had been “well” recently – no likely infectious syndrome on history.
The autoimmune diseases – SLE, PAN, Rh arthritis, Goodpasture’s, MCTD, etc – these all have a “syndrome” – other clinical features to tip you in that direction. So I would ask about: oral / mucosal ulcers, Raynaud’s, photosensitivity, joint symptoms, spontaneous miscarriages (more than 2?), undiagnosed anaemia, serositis: chest, pleurisy, abdo pain… the list is long but a lot of these minor features will be missed unless directly asked. Chest symptoms might direct you to Churg-Strauss, Wegener’s or Goodpasture’s if there is a cough, “new asthma”, haemoptysis etc. Odd neurological symptoms might point to SLE, PAN or sarcoidosis
Drugs: many drugs can trigger an immune-mediated vasculitis, and some can cause a serum sickness picture – so ask about anything recent: antibiotics, herbal / OTC preps, anything new..
Family history may be useful : ask about the chronic inflammatory joint, bowel diseases.
Specifically looking for features of the above diseases could take all day – but there is no cheaper test than looking in all available orifices for clues – eyes, ears, mouth, nose is a good start. Palpating joins to elicit a pattern of arthralgia might reveal a syndrome. The exam will largely be guided by the history.
A BP and urinalysis will help exclude any renal disease process, send some off to look for casts, protein etc.
This is one of those scenarios where you could spend a bunch of money on tests if you don’t think too hard. There is a temptation to do a screening batch of immuno-markers – ANS, ANCA, Ro, La, Anti-Rh, CCP….. you can do a thousand of them!
I think this is not the best strategy (though often used) – my plan would be to call my friendly immunology / rheumatology guy and outline exactly what I have heard and seen – then do the tess they think will help to confirm the diagnosis or exclude the really bad ones. These need to be directed by the clinical picture.
Xrays of affected joints occasionally show more chronic processes in action.
What about a biopsy? Well this seems crazy on first thought but it might be really useful in a week if you are still scratching your head. If you take an ellipse of he rash and ask for immunofluorescence etc then it might actually give a specific pattern. I think this could be useful
OK, let me know your backwards approach to this in your practice. Casey
I am a GP working in Broome, NW of Western Australia. I work as a hospital DMO (District Med Officer) doing Emergency, Anaesthestics, some Obstetrics and a lot of miscellaneous primary care. Also on the web as @broomedocs | + Casey Parker | Contact