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      Drugs & Diseases > Pediatrics: General Medicine

      Henoch-Schonlein Purpura (IgA Vasculitis) Workup

      Updated: Jan 30, 2023
      • Author: Rajendra Bhimma, MBChB, MD, PhD, DCH (SA), FCP(Paeds)(SA), MMed(Natal); Chief Editor: Craig B Langman, MD  more...
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      Workup

      Approach Considerations

      Diagnosis of IgA vasculitis (IgAV; Henoch-Schönlein purpura) is clinical and is not based on laboratory evaluation. Routine laboratory test results are usually within reference ranges. Some laboratory studies help in excluding other diagnoses and in evaluating renal function, including the following:

      • Urinalysis
      • Complete blood count (CBC) with platelet count and differential
      • Blood urea nitrogen (BUN) level
      • Creatinine level
      • Prothrombin time (PT)
      • Activated partial thromboplastin time (aPTT)
      • Lipase level 

      Some experts consider that imaging studies are indicated only if the diagnosis is uncertain. Kidney biopsy may be helpful in selected cases.

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      Laboratory Studies

      No specific diagnostic laboratory test is available to assess for markers of IgAV. General laboratory tests may reveal the following:

      • Antinuclear antibody (ANA) and rheumatoid factor (RF) - Absent
      • Factor XIII - Reduced in about 50% of patients
      • Urinalysis - Hematuria; proteinuria may also be found
      • CBC - Leukocytosis with eosinophilia and a left shift; thrombocytosis is present in 67% of patients
      • Platelet count - May be elevated; low platelet levels suggest thrombocytopenic purpura
      • Erythrocyte sedimentation rate (ESR) - Variably elevated; may be mildly elevated in as many as 75% of patients
      • Stool guaiac test - May reveal occult blood [95]
      • Blood urea nitrogen (BUN) and creatinine - May be elevated, indicating decreased kidney function
      • Amylase and lipase - May be elevated in patients with pancreatitis
      • Electrolytes - Generally in the reference range, but may be affected by excessive vomiting (eg, hypokalemia, hypochloremia)
      • Plasma D-dimer - May be substantially increased
      • Plasma thrombin-antithrombin (TAT) complex, prothrombin fragment (PF)–1, and PF-2 - May be abnormal
      • Prothrombin time (PT) and activated partial thromboplastin time (aPTT) - May be reduced (eg, hypoprothrombinemia)
      • Serum immunoglobulin A (IgA) - Increased in 50-70% of patients during the acute phase of illness; higher levels are associated with kidney involvement; circulating IgA immune complexes may be present in some patients, though data supporting the presence of classic antigen-antibody complexes have been questioned
      • Factor VIII - Decreased in some patients
      • Antistreptolysin O (ASO) - Elevated in 30% of patients
      • Complement studies - CH50 is decreased in 30% of patients; C3 and C4 are occasionally decreased
      • Immunocomplexes of IgG and IgA - May be increased

      Total IgA levels are not very helpful in confirming the diagnosis or providing prognostic information. Elevated serum levels of galactose-deficient IgA1 seem to distinguish IgAV patients with nephritis from those without nephritis, but this assay is not used presently in clinical practice. [96, 97]

      If serial urine samples are obtained in patients with IgAV, microscopic hematuria is usually found; it is probably present in 100% of cases. However, frank nephritis appears in only 20-30% of unselected children. The entire clinical spectrum of glomerulonephritis may occur in IgAV. The most common kidney manifestations are hematuria with mild-to-moderate proteinuria.

      Coppo et al reported that when severe proteinuria, hypertension, or crescents are present at onset, the risk of IgAV progression is greater in adults and females and appears linked with increasing mean proteinuria levels during follow-up, more so than in patients with decreased renal function at onset. [98] Factor XIII activity seems to correlate with severity of abdominal manifestations [99] ; thus, measuring such activity helps identify patients with severe gastrointestinal (GI) manifestations who might benefit from substitution therapy. [100, 101]

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      Ultrasonography

      Abdominal ultrasonography may be used if GI symptoms are present. It may be better than barium enema for diagnosing intussusception, in that IgAV-related intussusception is more likely to be ileoileal than ileocolic (as is typical of idiopathic intussusception). Diagnosis of IgAV using ultrasonography and radionuclide scanning in a child presenting with bilateral acute scrotum as the main symptom has been reported. In children with GI involvement of IgAV, dedifferentiated wall thickening on ultrasonography reveals a poor clinical prognosis. [102]

      Imaging of the scrotum by means of ultrasonography or a technetium radionuclide scanning may be necessary if scrotal edema is a presenting feature. Testicular ultrasonography may help in assessing the testes for hemorrhage or torsion. Doppler or radionuclide testicular scan results show normal or increased blood flow in IgAV, in contrast to the decreased blood flow seen in testicular torsion.

      Bowel ultrasonographic findings include thickening of the bowel wall, free fluid, and intussusception. Hydrops of the gallbladder is rarely seen. Kidney involvement may not be evident on ultrasonography; if nephritis or nephrotic syndrome occurs, however, enlargement of the kidneys with loss of corticomedullary differentiation due to edema is observed.

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      Radiography

      If hemoptysis has been noted, a chest radiograph should be obtained. Chest radiography may help in determining the presence and extent of pulmonary hemorrhage.

      Plain radiography of the abdomen may help in diagnosing intestinal obstruction. Contrast-enhanced radiography of the small intestine may demonstrate thickened mucosal folds or small barium flecks. Radiologic GI findings mainly include bowel ischemia with thumbprinting and bowel-wall edema, which is sometimes visible on abdominal radiographs.

      A barium enema study may be warranted for evaluating epigastric pain, hematemesis, and melena and for confirming and treating intussusception. If barium studies are performed, typical findings of ischemic colitis may be found, including a narrow colon with thickened mucosa and thumbprinting.

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      MRI and CT

      Magnetic resonance imaging (MRI) is useful for assessing neurologic findings in IgAV. In particular, MRI is the most sensitive imaging technique for posterior reversible encephalopathy syndrome (PRES), a clinico-radiological syndrome that may rarely complicate IgAV. The clinical manifestations of PRES include headache, seizures, visual disturbances, lethargy, confusion, stupor, and focal neurologic findings. MRI shows bilateral gray and white matter abnormalities suggestive of edema in the posterior regions of the cerebral hemispheres. [103]

      Computed tomography (CT) of the head is necessary if neurologic symptoms or severe headache persist. Abdominal CT may aid in the exclusion of other causes of abdominal pain.

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      Endoscopy

      Endoscopy may be needed to evaluate epigastric pain, hematemesis, and melena. Endoscopy may reveal multiple irregular ulcers, mucosal redness, and petechiae in the duodenum. The second part of the duodenum is sometimes predominantly affected. Ulcerating lesions accompanied by hematomalike protrusions can be detected in patients with histopathologically proven leukocytoclastic vasculitis.

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      Kidney Biopsy

      In some cases, kidney biopsy may be useful. It should be performed when nephrotic syndrome persists (though other manifestations may have subsided) and when kidney function deteriorates. When patients present with nephrotic syndrome, hypertension, and rapidly deteriorating kidney function, biopsy often shows circumferential crescents in most of the glomeruli. The extent of the crescents is of prognostic importance. Approximately 60% of patients develop kidney failure, either in the acute phase of the disease or after several years.

      The International Study of Kidney Disease in Children (ISKDC) classification is widely used for patients with IgAV nephritis. [20] Nephritis may be graded as follows:

      • Grade I - Minimal glomerular abnormalities
      • Grade II - Mesangial proliferation without crescents or sclerosing lesions
      • Grade III (a) - Focal segmental mesangial proliferation with < 50% crescents or sclerosing lesions   
      • Grade III (b) - Diffuse mesangial proliferation with < 50% crescents or sclerosing lesions
      • Grade IV - Mesangial proliferation with 50% - 70% crescents or sclerosing lesions
      • Grade V - > 75% crescents or sclerosing lesions
      • Grade VI - Membranoproliferative-like lesions

       

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      Histologic Findings

      Histopathologic features of the skin lesions in infantile IgAV can range from a typical leukocytoclastic vasculitis with or without fibrinoid necrosis to the less specific findings of a lymphohistiocytic perivascular infiltrate with extravasation of erythrocytes.

      Direct immunofluorescence (DIF) testing is a useful adjunct to histopathology; the yield is substantially higher when the test is performed within 48 hours of presentation. Immunofluorescence studies reveal perivascular IgA deposition in almost all patients; this finding is rare in infantile IgAV, in which C3 and IgM are most commonly found in the affected vessel walls.

      IgAV often involves the kidneys. Kidney histology in IgAV varies considerably. In some cases, most glomeruli appear unaffected on light microscopy; only a few show mesangial proliferation. In instances of moderate kidney involvement, focal and segmental intracapillary and extracapillary proliferation may be present with adhesions and small crescents. Severe cases are characterized by a diffuse proliferation with infiltration of neutrophils and circumferential crescents in most of the glomeruli. Tubular atrophy and interstitial infiltration with mononuclear cells may also be present.

      In most patients, IgA deposits in the mesangium and the walls of cutaneous capillaries are detected. The IgA deposited in the mesangium is mainly of the IgA1 subclass, though IgA2 deposits are noted in rare cases. In addition to IgA, the deposits in mesangium and cutaneous capillaries frequently contain C3, IgG, and fibrin. C3 deposits are often accompanied by properdin, whereas C1Q and C4 are usually not present. This observation suggests that the complement components have been activated by means of the alternative pathway.

      The specific kidney pathology of IgAV includes the following:

      • Diffuse hypercellularity
      • Focal and segmental proliferation
      • Mesangial proliferation
      • Minimal change to severe crescentic glomerulonephritis
      • Segmental sclerosis fibrosis
      • Mononuclear cell infiltration
      • Mesangial, subendothelial, and subepithelial deposits
      • Diffuse glomerular deposits of IgA, C3, fibrin, immunoglobulin G (IgG), properdin, and immunoglobulin M (IgM)
      • IgA deposits in the mesangium
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