Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis by Mary A. Williamson Mt(ascp) Phd, L. Michael Snyder Md Read Free Book Online

AL. Dermatomyositis and polymyositis: clinical presentation, autoantibodies, and pathogenesis. Ann N Y Acad Sci. 2010;1184:134–153.
PSORIATIC ARTHRITIS
   Definition
   Psoriatic arthritis (PsA) is a type of arthritic inflammation that occurs in approximately 15% of patients with psoriasis. It can affect any joint in the body causing pain, swelling, and stiffness. CD8 + T cells and T-cell-derived cytokines play a central role in the pathogenesis of PsA.
   The Classification Criteria for Psoriatic Arthritis (CASPAR) require the presence of joint, spine, or entheseal inflammatory disease plus a minimum score of 3 points from the following five categories (98.7% specificity and 91.4% sensitivity):
   Current psoriasis (2 points); personal or family history of psoriasis (1 point)
   Typical psoriatic nail dystrophy (1 point)
   Negative rheumatoid factor (1 point)
   Current dactylitis or history of dactylitis (1 point)
   Hand or foot plain radiography demonstrating juxta-articular new bone formation (1 point)
   Who Should Be Suspected?
   Most patients who develop PsA have skin symptoms of psoriasis first (erythematous papule and plaques with a silver scale), followed later by arthritis symptoms characterized by pain, tenderness, and stiffness in the joints and back.
   Several HLA types have been identified to be associated with PsA, suggesting a genetic predisposition. This is also indicated by the presence of a family history of psoriasis and psoriatic arthritis in up to 40% of patients.
   Laboratory Findings
    Laboratory finding are not specific.
   ESR and CRP are elevated in approximately 50% of cases; levels correlate with the number of involved joints.
   RF is negative.
   Anemia of inflammation, hypergammaglobulinemia with increased IgA levels, and hypoalbuminemia have been reported in some cases.
   Hyperuricemia, related to either increased skin cell turnover or metabolic defect, is found in nearly 20% of patients.
   HLA testing can be helpful: HLA Cw6 is the most important allele for susceptibility to early-onset psoriasis; HLA-B17 may be associated with a more severe phenotype.
Suggested Reading
Cantini F, Niccoli L, Nannini C, et al. Psoriatic arthritis: a systematic review. Int J Rheum Dis. 2010;13(4):300–317.
REACTIVE ARTHRITIS
   Definition
   Reactive arthritis, formerly known as Reiter syndrome, is an autoimmune spondylarthritis that develops 1–4 weeks after an infection with a pathogen elsewhere in the body. Most often, causing pathogens are urogenital (e.g., Chlamydia ) or enteric (e.g., Campylobacter , Salmonella , Shigella , or Yersinia ).
   Who Should Be Suspected?
   A likely patient is a young adult (20– 40 years of age) who develops postinfectious asymmetric oligoarthritis (affecting most often the knees, ankles, and heels), enthesitis, dactylitis, and lower back pain. In addition, patients may have extra-articular signs including urinary (urethritis, balanitis, dysuria, prostatitis in men, cervicitis, salpingitis or vulvovaginitis in women), ocular (conjunctivitis or anterior uveitis), and/or constitutional (malaise, fever, weight loss) symptoms.
   Laboratory Findings
    Diagnosis is primarily clinical.
   Culture and serology tests are helpful in identifying the infectious etiology of the disease in only a fraction of cases since pathogens may no longer be retrievable by the time arthritis develops. Nevertheless, a trial to identify the following pathogens by stool or urine cultures, or in some cases by serology, should be attempted:
    Chlamydia , especially Chlamydia trachomatis and Chlamydia pneumoniae . PCR for urinary Chlamydia DNA has high sensitivity.
    Yersinia enterocolitica and Yersinia pseudotuberculosis .
    Salmonella of various serovars.
    Shigella , especially Shigella flexneri and Shigella dysenteriae .
    Campylobacter , especially Campylobacter jejuni .
    Clostridium difficile