Pathogenesis of ANCA Associated Vasculitis

Antineutrophil cytoplasmic autoantibodies (ANCAs) are associated with, and are the probable cause of, a distinct form of vasculitis that can affect any organ in the body. Although small vessels are the predominant target, ANCA-associated vasculitis (AAV) can affect many different types of vessels including arteries, arterioles, capillaries, venules and veins.  Immunopathologically, AAV has an absence or paucity of immunoglobulin deposition in injured vessels (pauci-immune vasculitis), compared with the more extensive deposition of immunoglobulin in immune-complex-mediated small-vessel vasculitis.1 AAV can be limited to one organ at the time of presentation (for example, lung-limited disease or renal-limited disease) or involve multiple organs. Frequent target tissues are the upper and lower respiratory tract, kidneys, skin and peripheral nerves. Onset and exacerbations induce signs and symptoms of high levels of circulating inflammatory cytokines, such as fever, arthralgia and myalgia. In addition to these nonspecific systemic inflammatory manifestations, inflammation of vessel walls causes more specific signs and symptoms of vasculitis depending on which vessels and which organs are affected, for example purpura caused by dermal venulitis; pulmonary haemorrhage caused by alveolar capillaritis; glomerulonephritis caused by glomerular capillaritis; peripheral neuropathy caused by epineural arteritis; and ocular inflammation caused by vasculitis in small vessels in the eye and orbit. In addition to vasculitis, some variants of ANCA-associated disease have extravascular necrotizing granulomatous inflammation (granulomatosis)—seemingly not arising from vascular inflammation—that most often affects the upper and lower respiratory tracts but can affect any organ.

AAV can also be classified on the basis of autoantigen specificity. In patients with vasculitis, the two best-documented autoantigen targets of ANCA are myeloperoxidase (MPO) and proteinase 3 (PR3). Classification of AAV by antigen specificity clearly shows differences in clinical presentations and outcomes, organ system involvement, patterns of extravascular inflammation, and genetic associations including HLA associations.

An important role for ANCAs in the pathogenesis of vasculitis and glomerulonephritis is supported by clinical evidence and by in vitro and in vivo experimental data. The leading theory proposes that circulating neutrophils and monocytes that have been primed by inflammatory stimuli display ANCA antigens at or near the cell surface, and that interaction of these antigens with ANCAs results in neutrophil activation and initiation of vascular inflammation. An extension of this theory proposes that primed extravascular neutrophils interact with interstitial ANCAs, causing necrotizing inflammation and resultant reactive granulomatous inflammation.

ANCA
Nature Reviews Rheumatology | 10, 463–473 | (2014) doi:10.1038/nrrheum.2014.103 | Published online 08 July 2014

For more information, visit Nature 

UTSW Resident Publishes in JAMA Internal Medicine!

One of our residents, Udayan Shah (PGY-01), published an article online in JAMA Internal Medicine this week, “When Documentation Supersedes Patient Communication – An Example From An Endoscopy Unit” along with Dr. Deepak Agrawal from the division of Digestive and Liver Disease at UT Southwestern. The article focuses on question surveys that providers ask to patients including physicians and nurses. The authors discuss the utility of these surveys to patient care and why these surveys have become common in health care settings. Are these surveys mandated by an authorizing body like CMS or the Joint Commission? Do these surveys lead to better patient care and outcomes? Check out the article below to read more about this!

udayan shah

Disseminated Histoplasmosis

  • Basic Information

    • AIDS defining illness and typically seen in HIV patients with CD4<100 cells/microL.
    • The fungus (Histoplasma capsulatum) is found in soil contaminated with bird or bat excreta and transmission occurs from inhalation of spores.
    • Thought to be endemic in Ohio, Mississippi, Caribbean, Mexico, Asia, and Central/South America.
  • Clinical Manifestations

    • Immunocompromised hosts can present with more severe symptoms: fevers, night sweats, nausea, vomiting, dyspnea.
    • 50% of AIDS patients with disseminated histoplasmosis have pulmonary involvement.
  • Diagnosis

    • Elevated LFT’s, LDH, and ferritin are commonly seen. Elevated creatinine is considered a poor prognostic factor.
    • Although the initial chest x-ray often looks normal, may see diffuse interstitialor reticulonodular infiltrates.
    • Most sensitive and specific test for suspected disseminated histoplasmosis in an HIV patient is histoplasmosis antigen detection.
    • Histoplasmosis antigen can be detected in fluids including urine, serum, cerebrospinal fluid.
  • Management

    • Rapid initiation of treatment is important and includes induction and maintenance phases. Amphotericin B is typically used for induction for 1-2 weeks. Therapy is then switched to itraconazole for consolidation and long-term suppression.
    • 2009 IDSA guidelines recommend primary prophylaxis with itraconazole for HIV patients with CD4<150.