Investigations
1st investigations to order
immunofluorescence antigenic mapping
Test
Performed on a cryopreserved skin biopsy specimen obtained from a freshly induced lesion.
Performed on all infants with epidermolysis bullosa (EB) in whom lack of positive family history prevents accurate sub-classification.
Separates the condition into the main types of EB.[36]
There is a 97% concordance with transmission electron microscopy.
The most common antigenic abnormalities are absent expression of type VII collagen, laminin-332, plectin, and kindlin-1 in, respectively: severe recessive dystrophic EB; intermediate junctional EB; EB simplex with muscular dystrophy (EBS-MD); and Kindler's EB.[3]
Reduced expression of type VII collagen may be seen in intermediate recessive dystrophic EB, and RDEB, inversa skin, whereas reduced expression of laminin-332 or type XVII collagen may be seen in intermediate junctional EB.[3]
Intra-epidermal granular staining of type VII collagen is diagnostic of dystrophic EB, bullous dermolysis of the newborn (DEB-BDN).[45][46]
Result
altered staining with specific antibodies
DNA mutational analysis
Test
Now routinely performed, and no longer limited to the setting of antenatal diagnosis and pre-implantation in-vitro fertilisation.[3][36] Whole-exome sequencing facilitates enabling rapid and efficient genetic diagnosis for patients with suspected EB, with gene panels for EB being established in specialised centres.[8]
Result
gene mutation(s) detected and mode of transmission identified
transmission electron microscopy
Test
The test may be used, instead of immunofluorescence antigenic mapping, to distinguish between the main types of EB.[36]
Semi-quantification of specific structures will assist in the sub-classification of EB patients.[3][9]
Result
absence of hemidesmosomes and anchoring fibrils is suggestive of severe junctional EB and severe recessive dystrophic EB; presence of stellate deposits in peri-nuclear array within keratinocytes is diagnostic of dystrophic EB, bullous dermolysis of the newborn (DEB-BDN); clumped tonofilaments within keratinocytes are diagnostic of EB simplex, generalised severe (EBS-gen sev)
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