Sunday, November 11, 2012

The Vasculitides: Churg-Strauss Syndrome (CSS)

Churg-Strauss syndrome is a small vessel vasculitis that represents a combined allergic granulomatosis and angiitis.  Definition of the syndrome has altered over time, but according to a recent classification scheme it has been included in the same group as Wegener's granulomatosis and microscopic polyangiitis, both of which are strongly associated with anti-neutrophil cytoplasmic antibodies (ANCA), but whether Churg-Strauss truly belongs to this group is still yet to be definitively determined.

A multisystem disorder -- like all the vasculitides -- the manifestations of Churg-Strauss can be protean, but the most commonly symptomatic organ is the lungs, and eosinophilic asthma is considered a hallmark of the disease.

The American College or Rheumatology included "non-fixed pulmonary infiltrates on chest radiography" in 1990 as one of the six criteria for Churg-Strauss (4+/6 has a sensitivity of 85% and specificity of 99.7%)...

1) asthma
2) eosinophilia of greater than 10% of the peripheral WBC count
3) mononeuropathy or polyneuropathy
4) non-fixed non-fixed pulmonary infiltrates on chest radiography
5) paranasal sinus abnormalities
6) biopsy containing a blood vessle with extravascular eosinophils

... but not every diagnosis scheme for Churg-Strauss includes imaging, and some of the alternate schemes claim a similar or better sensitivity and specificity.

This isn't totally surprising, because the radiographic findings in Churg-Strauss are incredibly nonspecific. The most commonly correlated findings on Chest CT are nonspecific groundglass opacities, usually with a peripheral distribution... or centrilobular nodules and tree-in-bud opacities, almost equally as nonspecific. Both the upper and lower lung zone can be affected, but the symptoms are usually more mild than with Wegener's granulomatosis. Cavitary nodules are reported as rare in Churg-Strauss, and if cavitary nodules are present, another etiology (e.g. Wegener's) should be entertained.

An HRCT image from an 58Y asthmatic lady who had been diagnosed with Churg-Strauss Syndrome.  The multifocal, nonsegmental centrilobular nodules and tree-in-bud opacities (green ovals) are compatible with Churg-Strauss syndrome, but are completely nonspecific and cannot be separated from other infectious/inflammatory etiologies.

Two slices from a chest CT in a 47Y lady diagnosed with Churg-Strauss syndrome.  She had a long history of waxing and waning peripheral ground glass opacities, similar to those seen above.  Ground glass opacities have been linked to small foci of alveolar hemorrhage (capillaritis).

In addition to the respiratory tract, other organs that can be affected include the skin, the heart, and the nervous system.  Mononeuritis multiplex is the classic peripheral neurologic finding associated with vasculitis, but central CNS changes can also be seen, although they also tend to be nonspecific.

T2 FLAIR image from a 57Y man with diagnosed Churg-Strauss syndrome, presenting with headache.  The tiny white matter signal abnormalities in the frontal lobes are not incompatible with a small vessel vasculitis... but they're also compatible with many other more common conditions, such as migraine headache.

Part of the difficulty in coming to a definitive conclusion regarding Churg-Strauss is that it is a rare syndome.  Asthma usually precedes the vasculitis, but other than that, there is a range of age presentation and the male:female ratio is 1:1. 

1. "Vasculitis" Ball GV and Bridges SL. (2002)
2. Jeong YJ, Kim KI, Seo IJ, et al. "Eosinophilic Lung Diseases: A Clinical, Radiologic, and Pathologic Overview" RadioGraphics 2007; 27:617–639
3.  Worthy SA, Muller NL, Hansell DM, Flower CDR. "Churg-Strauss Syndrome: The Spectrum of Pulmonary CT Findings in 17 Patients" AJR 1998;1 70:297-300