Vasculitis - one of the great mimickers

Thank you very much to St. Michael's Hospital and Dr. Yuna Lee's team for inviting me to do morning report (at lunch time!) at their amazing hospital!

We discussed a very interesting case of a patient presenting with a subacute mononeuropathy that ended up being diagnosed with microscopic polyangiitis (MPA).  This brought up a very interesting discussion of vasculitis and the different clinical presentations that patients often present with.  As a general internist, one of the most important methods of diagnosing a vasculitis is having an index of suspicion, and being aware of the different patterns that each vasculitis often presents with.

Vasculitis is a rare, and is a mimicker of many common conditions such as atherosclerotic disease, infections such as endocarditis, and viral infections.  The most helpful way to organize a basic approach to vasculitis is to think about the size of the vessel that the particular disease is affecting, from small vessel all the way up to large vessel.

Small Vessel:

Palpable Purpura

Microscopic Polyangiitis (MPA) - often presents with pulmonary-renal syndrome.  Can present with neuropathies as well.  Many patients with MPA will have positive p-ANCA or anti-MPO antibodies.


GPA (formerly Wegener's) - Again, often presents with pulmonary and renal involvement.  Also involves the nose/sinuses.  These patients can present with diffuse alveolar hemorrhage, and occasionally require ICU admissions.  Patients with GPA often have c-ANCA positivity, or anti-PR3 antibodies.  The classic rash seen in small vessel vasculitis is palpable purpura.

EGPA (formerly Churg-Strauss) - The clinical presentation is similar to GPA, but often there is a history of reactive airway disease or asthma.  These patients also have chronically elevated eosinophils, which is the main differentiation from GPA.

Anti-GBM (formerly Goodpastures) - presents very similar to GPA with pulmonary-renal syndrome.  Does not involve the nasopharynx typically.

Medium Vessel:

Livedo reticularis

In adults, the classic diagnosis is PAN (polyarteritis nodosa).  These patients often present with mesenteric ischemia, testicular pain, and the classic rash is livedo reticularis.  They often get involvement of axonal neurons resulting in wrist drops, and foot drops (mononeuritis multiplex).  PAN also classically has an association with Hepatitis B.

Kawasaki's disease is the other classic medium vessel vasculitis that presents in childhood, and occasionally early adulthood.

Large Vessel:

Takayasu's disease is a large vessel vasculitis that often affects younger women of Asian descent, which is the classic phenotype.  These patients often present with absent pulses (radial, ulnar) and can get symptoms of intermittent claudication (of upper and lower extremities).  They may also have blood pressure differences between the various limbs.

Giant Cell Arteritis - This is classic and relatively common large vessel vasculitis.  This typically presents in individuals over the age of 55 with nonspecific constitutional symptoms.  There is a strong association with PMR.  The classic symptoms patients will complain of include diplopia, headache, and jaw claudication.

Vasculitis is a large and interesting field that is very near and dear to the heart of internists in Toronto.  The UHN/Sinai's own Dr. Simon Carette and Dr. Christian Pagnoux are world experts in the field of vasculitis research!

Other clinical pearls that I've learned from rotating through the rheumatology service at UHN under the watchful eye of Dr. Carette are the following:

The classic CBC pattern that you will see in a patient (it is not-specific) but may be a clue that a vasculitis is occurring, is anemia of chronic disease (Hb in the 90-110 range) along with a mildly elevated leukocytosis (11.5-14 range) and a reactive thrombocytosis (450-650 range).  This pattern is non-specific, but is common in patients with chronic infections (osteomyelitis, and systemic illness likely vasculitis).  This is contrast to a patient presenting with SLE where cytopenia is the classic hematolgic manifestation (thrombocytopenia, anemia, lymphopenia)

Atherosclerosis is common!  atherosclerosis  is by far and away the most common cause of "disease of the blood vessels".  The vast majority of patients with ischemic limbs, mesenteric angina, and stroke have underlying atherosclerotic risk factors (HTN, diabetes) and this can masquerade as a "vasculitis".  As the old saying goes, when you hear hoof steps, its more likely to be a horse than a zebra (unless the case is being presented in morning report!)

Think about vasculitis in patients with multiple organ systems involved, particularly the classic pulmonary-renal syndromes.  Also, many clues to an underlying vasculitis often lie in the skin (palpable purpura, livedo reticularis, etc.) and so a consult with dermatology for skin biopsies can often lead to a diagnosis.


Reference:
http://www.canvasc.ca/