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Linear IgA disease is a blistering disorder of the skin and mucous membranes.
Tests generally appear in the order most useful for common clinical situations
| Test name: Cutaneous Direct Immunofluorescence, Biopsy |
| ARUP #: 0092572 |
| Methodology: Direct Immunofluorescence (Direct Fluorescent Antibody Stain) |
| Use: Determine presence and staining pattern of immunoglobulins (IgG, IgM, IgA), third component of complement (C3) and fibrinogen in perilesional skin or mucosal biopsy specimens from patients suspected of having linear IgA disease |
| Limitations: May be inaccurate if tissue not taken from correct perilesional location; specimen must have epidermis/epithelium and basement membrane zone (BMZ) Tissue must be submitted in Michel’s or Zeus medium; this test cannot be performed on formalin-fixed tissue |
| Follow-up: Concurrent serum testing with pemphigoid panel is the most sensitive for diagnosis and for determining subtype of subepidermal blistering disease Patients with indeterminate results should have repeat biopsy by direct immunofluorescence (DIF) and antibody levels monitored for disease activity |
| Test name: Pemphigoid Panel - Epithelial Basement Membrane Zone IgG & IgA, BP180 & BP230 IgG Antibodies |
| ARUP #: 0092001 |
| Methodology: Enzyme-Linked Immunosorbent Assay/Indirect Fluorescent Antibody |
| Use: Diagnose most types of pemphigoid, epidermolysis bullosa acquisita, linear IgA disease (including linear IgA bullous dermatosis and childhood immunobullous disease) Panel includes epithelial BMZ IgG & IgA antibodies by indirect immunofluorescence (IFA) on split human skin and monkey esophagus substrates, BP180 & BP230 IgG antibodies by ELISA Use in conjunction with pemphigus panel and endomysial antibody IgA testing to differentiate among the immunobullous skin diseases in patients suspected or known to have any type of immunobullous disease IgG BP180 and BP230 antibody levels may be useful in monitoring disease activity and response to therapy |
| Limitations: Clinical correlation is necessary because the incidence of false-positives, although rare, increases with age Because of clinical overlap among immunobullous diseases and similar names, testing for pemphigoid may be confused with testing for pemphigus and misordered |
| Follow-up: Perilesional skin biopsy by DIF is helpful in diagnosis (>90% of pemphigoid and epidermolysis bullosa acquisita cases are positive) Use pemphigoid panel to monitor pemphigoid disease activity and response to therapy |
| Test name: Pemphigus Panel - IgG Epithelial Cell Surface Antibodies and Levels of IgG Desmoglein 1 and Desmoglein 3 Antibodies, Serum |
| ARUP #: 0090650 |
| Methodology: Enzyme-Linked Immunosorbent Assay/Indirect Fluorescent Antibody |
| Use: Diagnose most types of pemphigus and monitor disease activity and response to therapy Panel tests for IgG epithelial cell surface antibodies by IFA on intact human skin and monkey esophagus substrates and IgG desmoglein 1 and IgG desmoglein 3 antibodies by ELISA |
| Limitations: Clinical correlation is necessary because cell surface antibodies by IFA, usually in low titers, may be found in normal individuals (possible blood group reactivity) or in patients with fungal infections, burns, drug reactions and other dermatoses Because of clinical overlap among immunobullous diseases and similar names, testing for pemphigus may be confused with testing for pemphigoid and misordered; testing for IgG pemphigus antibody types (most common) also may be confused with IgA pemphigus testing (rare disorder) |
| Follow-up: Concurrent perilesional skin biopsy evaluated by DIF is important for diagnosis because of increased sensitivity (85-100% of pemphigus, pemphigoid, linear IgA disease, epidermolysis bullosa acquisita, and dermatitis herpetiformis cases are positive) Use pemphigus panel to monitor disease activity and response to therapy |
| Test name: Tissue Transglutaminase (tTG) Antibody, IgA with Reflex to Endomysial Antibody, IgA by IFA |
| ARUP #: 0050734 |
| Methodology: Semi-Quantitative Enzyme-Linked Immunosorbent Assay/Semi-Quantitative Indirect Fluorescent Antibody |
| Use: Use along with pemphigoid and pemphigus panel tests, or epithelial skin antibody testing to differentiate among the immunobullous skin diseases in patients suspected or known to have any type of immunobullous disease |
| Limitations: Will not detect IgA or other BMZ antibodies that characterize linear IgA disease |
| Follow-up: Perilesional skin biopsy by DIF is helpful in diagnosis (>90% of dermatitis herpetiformis cases are positive) |
| Test name: Epithelial Basement Membrane Zone IgA Antibodies |
| ARUP #: 0092057 |
| Methodology: Indirect Immunofluorescence (Indirect Fluorescent Antibody) |
| Use: Discriminate among clinically similar immune-mediated skin diseases such as linear IgA disease, pemphigoid, epidermolysis bullosa acquisita and dermatitis herpetiformis in patients suspected of having or known to have any type of subepidermal immunobullous disease Monitor treatment response |
| Limitations: Although helpful in screening for immunobullous disease, not as sensitive as combination of pemphigus and pemphigoid panels |
| Follow-up: Perilesional skin biopsy by DIF may be necessary for final clinical diagnosis |
| Test name: Epithelial Skin Antibody |
| ARUP #: 0090299 |
| Methodology: Indirect Immunofluorescence (Indirect Fluorescent Antibody) |
| Use: Use along with endomysial antibody IgA test to differentiate among immunobullous skin diseases in patients suspected or known to have any type of these disorders Panel includes epithelial BMZ IgG & IgA antibodies by IFA and IgG & IgA cell surface antibodies by IFA on split human skin, intact human skin and monkey esophagus substrates |
| Limitations: Does not include testing for antibodies to target antigens, BP180 & BP230 for pemphigoid and desmoglein 1 & 3 for pemphigus that may be more sensitive and the levels of which correlate with disease activity and response to therapy |
| Follow-up: Perilesional skin biopsy by DIF is helpful in diagnosis (85-100% of linear IgA disease, pemphigoid, pemphigus, dermatitis herpetiformis and epidermolysis bullosa acquisita cases are positive) |