Evidence of an underlying systemic inflammation may be indicated by elevated acute phase reactants, especially the erythrocyte sedimentation rate, but also the white blood cell count, platelet count, and C-reactive protein. The complete blood count may demonstrate a normochromic, normocytic anemia of chronic disease. These laboratory findings are nonspecific for any particular rheumatologic diagnosis. Certain laboratory tests may help confirm a diagnosis, such as autoantibody production in SLE or muscle enzyme elevation in JDM, or identify increased risk for complications, such as uveitis in a patient with JIA with a positive antinuclear antibody.
Radiologic studies should focus on areas of concern identified by history or physical examination. Radiography of jointsin patients with arthritis on examination may be beneficial,but radiographic abnormalities may lag far behind the clinicalexamination. Tests with greater sensitivity, such as bone scan,computed tomography scan, and magnetic resonance imaging,may be useful when trying to differentiate between synovitisand traumatic soft tissue injury. Magnetic resonance imagingmay also be useful to identify evidence of central nervous system involvement with SLE or for evidence of myositis with JDM.
Henoch-Schönlein purpura (HSP) is a vasculitis of unknown etiology characterized by inflammation of small blood vesselswith leukocytic infiltration of tissue, hemorrhage, and ischemia.The immune complexes associated with HSP are predominantlycomposed of IgA.
HSP is the most common systemic vasculitis of childhood and cause of nonthrombocytopenic purpura, with an incidence of 13 per 100,000 children. It occurs primarily in children 3 to 15 years of age, although it has been described in adults. HSP is slightly more common in boys than girls and occurs more frequently in the winter than in the summer months.
Available @ StudentConsult.com
HSP is characterized by rash, arthritis, and, less frequently, gastrointestinal or renal vasculitis. The hallmark of HSP is palpable purpura, caused by small vessel inflammation in the skin leading to extravasation of blood into the surrounding tissues, frequently with IgA deposition. The rash is classically found in dependent areas: below the waist, on the buttocks, and lower extremities (Fig. 87-1). The rash can begin as small macules or urticarial lesions but rapidly progresses to purpura with areas of ecchymosis. The rash also can be accompanied by edema, particularly of the calves and dorsum of the feet, scalp, and scrotum or labia. HSP occasionally is associated with encephalopathy, pancreatitis, and orchitis.
Arthritis occurs in 80% of patients with HSP and is most common in the lower extremities, particularly the ankles and knees. The arthritis is acute and very painful with refusal to bear weight. Joint swelling can be confused with peripheral edema seen with the rash of HSP.
Gastrointestinal involvement occurs in about one half of affected children and most typically presents as mild to moderate crampy abdominal pain, thought to be due to small vessel involvement of the gastrointestinal tract leading to ischemia. Less commonly, significant abdominal distention, bloody diarrhea, intussusception, or abdominal perforation occurs and requires emergent intervention. Gastrointestinal involvement is typically seen during the acute phase of the illness. It may precede the onset of rash.
One third of children with HSP develop renal involvement, which can be acute or chronic. Although renal involvement is mild in most cases, acute glomerulonephritis manifested by hematuria, hypertension, or acute renal failure can occur. Most cases of glomerulonephritis occur within the first few months of presentation, but rarely patients develop late renal disease, which ultimately can lead to chronic renal disease, including renal failure.