DNA based molecular analysis in the rapid diagnosis of Herlitz junctional epidermolysis bullosa

[Bart syndrome associated to lethal junctional epidermolysis bullosa (Herlitz form)]

We present the case of a newborn with congenital absence of skin in the anterior part of the left leg that shortly after developed bulla and erosions in hands, feet, ears, buttocks and mouth. The cutaneous biopsy and ultrastructural and immunohistochemical studies showed a subepidermal bulla in the lamina lucida, absence of hemidesmosomes and marked decrease of laminin 5, thus establishing the diagnosis of Bart syndrome associated to the Herlitz form of lethal junctional epidermolysis bullosa. Bart syndrome consists of congenital and localized absence of skin, nail abnormalities and mucoc-cutaneous bullae. It is usually associated to dystrophic epidermolysis bullosa. The Herlitz form of junctional epidermolysis bullosa is a rare variant, usually lethal that is produced by mutations in the genes coding for the anchor protein laminin 5. To our knowledge this is the second case that reports an association between Bart syndrome and lethal junctional epidermolysis bullosa and the first in which the results of immunofluorescence mapping are published.

Paternal germline mosaicism in Herlitz junctional epidermolysis bullosa

We studied a single patient with the lethal (Herlitz) type of junctional epidermolysis bullosa (H-JEB). Screening for mutations in the LAMB3 gene in the patient revealed the previously described hotspot mutation R635X and a novel one basepair deletion in exon 10. The single basepair deletion 1094delA could be detected in the clinically unaffected mother, while the nonsense mutation R635X could not be found in the peripheral blood DNA of either parent. After excluding non-paternity by microsatellite analysis using random markers on chromosomes 3, 8 and 18, we determined that the mutation R635X in the proband was most likely the result of a de novo event or alternatively, germline mosaicism. The parents requested prenatal diagnosis for a second pregnancy, and while the maternal mutation 1094delA could not be detected in DNA from the fetus, unexpectedly, the mutation R635X was present in the chorionic villus DNA. These findings were most consistent with paternal germline mosaicism for the recessive mutation R635X. The results have had a significant impact on the genetic counseling in this family. To our knowledge, this study represents the first documented case of germline mosaicism in junctional epidermolysis bullosa, and serves as a reminder that germline mosaicism should be considered in cases in which a 'new' mutation is found in the offspring of a clinically and/or genetically unaffected parent.