Nonsense-associated altered splicing of the Patched gene fails to suppress carcinogenesis in Gorlin syndrome.

Mutations in the gene coding for the transmembrane receptor protein Patched (PTCH) are implicated in the autosomal dominant disorder Gorlin syndrome (also known as naevoid basal cell carcinoma syndrome), characterized by congenital abnormalities and cancer predisposition. Tumour promotion is thought to be associated with aberrant function of PTCH, leading to misregulation of the hedgehog signalling network. However, the transcriptional events that underlie the reduced tumour suppression effects of PTCH have not been studied in detail. We describe a patient with Gorlin syndrome who had three molecular aberrations resulting in biallelic disruption of the PTCH gene, leading to abnormal protein expression and development of basal cell carcinoma. Remarkably, within tumour cells, the somatic nonsense mutation G1019X was associated with activation of a cryptic splice donor site, in which an in-frame deletion of the exon sequence containing the nonsense mutation occurred. However, the function of the resulting PTCH protein variant was still compromised. The pathogenetic alterations described give insights into the sequence of events leading to cellular transformation and underscore the importance of the PTCH protein in skin homeostasis.

Introducing a fast and simple PCR-RFLP analysis for the detection of mutant thiopurine S-methyltransferase alleles TPMT*3A and TPMT*3C.

BACKGROUND: Azathioprine, in combination with corticosteroids, is the first-line therapy of severe forms of pemphigus vulgaris. Patients with an impaired thiopurine S-methyltransferase (TPMT) activity are at risk of developing severe myelo-suppression upon treatment with thiopurines such as azathioprine. Analysis of the TPMT status prior to drug administration is therefore highly recommended. However, because of the limited availability of TPMT testing outside of specialized centres, pre-emptive TPMT testing is not widespread. To avoid laborious biochemical and sequencing assays, we evaluated a new restriction fragment length polymorphism (RFLP) analysis. METHODS: We designed a rapid genetic polymerase chain reaction (PCR)-RFLP screen for the most prevalent mutant TPMT*3A and TPMT*3C alleles that are known to result in reduced TPMT enzyme activity. RESULTS: Validating our fast system on 871 Caucasian DNA samples, we observed that 8.61% of our probands carried the TPMT*3A allele and 0.23% were heterozygous for the TPMT*3C allele, which is in concordance with previously reported allele frequencies. CONCLUSION: This simple and low-cost PCR-RFLP TPMT polymorphism testing approach can be performed in a standard laboratory. It should be applied to all patients prior to receiving thiopurine drug therapy to avoid the severe, but predictable, haematopoietic side-effects of thiopurine drug administration.

Epidermolysis bullosa naevi reveal a distinctive dermoscopic pattern.

BACKGROUND: Large, asymmetrical and irregularly pigmented naevi in patients with epidermolysis bullosa (EB) have been reported often to mimic cutaneous melanoma clinically. OBJECTIVES: As the biological course of these peculiar moles is benign, we assessed EB naevi with a dermatoscope to determine whether they could be reliably differentiated from cutaneous melanoma. METHODS: We evaluated digital dermoscopic images of 23 EB naevi from 11 patients with EB and analysed these pigmented lesions according to pattern analysis, ABCD rule of dermoscopy and the seven-point checklist. RESULTS: Melanoma-associated dermoscopic criteria such as multicomponent pattern (20 of 23), atypical pigment network (17 of 23), irregular dots/globules (16 of 23), irregular pigmentation (22 of 23) and an atypical vascular pattern (seven of 23) were frequently seen in EB naevi. In contrast, other criteria frequently associated with melanoma progression, such as irregular streaks, blue-whitish veil, regression structures (blue-whitish areas) or black dots, were rarely seen. Most lesions gave false-positive results when the scores of the dermoscopic diagnostic algorithms were calculated. CONCLUSIONS: Recurring dermoscopic structures in EB naevi reveal a distinctive dermoscopic pattern of this recently defined entity. Although EB naevi represent an exception to dermoscopic diagnostic algorithms, their dermoscopic evaluation most often allows us to estimate their benign nature. Nevertheless, as an unequivocal discrimination from malignant melanoma in vivo is sometimes not possible, regular clinical follow up of EB naevi with histopathological evaluation of highly suspicious lesions is mandatory.

Telepathology using immunofluorescence/immunoperoxidase microscopy.

We evaluated low-cost, store-and-forward telepathology interpretation of digital images of skin sections stained immunohistochemically, using immunofluorescence (IF) and immunoperoxidase (IP). The sample comprised 17 patients with skin diseases characterized by cutaneous deposition of immunoglobulins, fibrinogen or complement components. Up to 11 digital IF or IP images (median 3) were transferred via email to centres in Graz, Austria, and Kurume, Japan. Both remote centres had expertise in reading immunohistochemical specimens. Although image files were relatively small (approximately 100 kByte), the IF images were of high quality and they were well suited to static telepathology. There was agreement on the diagnoses made by the local and both remote centres by physicians experienced in IF/IP microscopy in 14 of 17 cases (82%). These results suggest that telepathology evaluation of immunohistochemical specimens may be a useful procedure for the discussion of unusual skin disorders, training purposes and second-opinion consultations on difficult cases from centres of excellence in immunohistochemical diagnosis.

Interaction between the immune system and tumor cells: cutaneous disorders as a consequence of autoimmunity and immunosuppression.

The interaction between the immune system and tumor cells is discussed with regard to examples of lymphoproliferative disorders associated with autoimmune phenomena, immunosuppression favoring tumorigenic infections, and a new therapeutic modality whereby a drug-induced Th1 immune response leads to complete regression of skin tumors.

Characteristic immunohistochemical and ultrastructural findings indicate that Kindler's syndrome is an apoptotic skin disorder.

BACKGROUND: Kindler's syndrome is a rare genodermatosis mainly characterized by the onset of skin blistering in early childhood, web formation of fingers and toes, photosensitivity, and progressive poikiloderma. There is still debate whether this disease represents a distinctive entity in the spectrum of congenital bullous poikilodermas or a variant of dystrophic epidermolysis bullosa. OBJECTIVE: To evaluate the recently proposed and debated characteristic immunohistochemical and ultrastructural features of Kindler's syndrome. PATIENT/METHODS: Immunofluorescence (IF) antigen mapping and transmission electron microscopy (TEM) were performed on a skin specimen from non-sun-exposed inner aspect of the upper arm of a 49-year-old patient with characteristic clinical features of Kindler's syndrome. RESULTS: IF studies revealed focally an extensively broadened, partly reticular staining pattern in the dermoepidermal basement membrane zone (BMZ) with antibodies against laminin-5 and type IV as well as type VII collagen. Anti-alpha6 and beta4 integrin staining revealed small gaps in the linear reactivity in the BMZ. Abundant keratin bodies, as detected by anti-immunoglobulin M (IgM) staining, were focally present in the dermis, indicating prominent epidermal apoptosis. This was verified by a histochemical apoptosis stain [terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) reaction]. Transmission electron microscopic examination showed manifold reduplications of the lamina densa (with attached anchoring fibrils) as well as a keratin body surrounded by a fibroblast in the upper dermis. CONCLUSION: We present characteristic immunohistochemical and ultrastructural features of Kindler's syndrome identical to those described by Shimizu et al. and provide evidence that Kindler's syndrome might primarily be an apoptotic disorder of basal keratinocytes.

Type XVII collagen gene mutations in junctional epidermolysis bullosa and prospects for gene therapy.

Non-Herlitz junctional epidermolysis bullosa (nH-JEB) is caused predominantly by mutations leading to premature stop codons on both alleles of the type XVII collagen gene (COL17A1). The analysis of mutations in this gene has provided a means of correlating genotype with phenotype of nH-JEB patients. The phenotype of nH-JEB is characterized by generalized blistering of skin and mucous membranes with atrophic scarring and nail dystrophy. Atrophic alopecia is a distinct feature of nH-JEB patients, but one that is not associated with the severity of the disease at other sites. Enamel hypoplasia and pitting of the teeth are also characteristic for nH-JEB and can be used to facilitate the correct diagnosis in children with a blistering skin disease. Analysis of the biological consequences of mutations in the COL17A1 gene has shown that most patients lack type XVII collagen mRNA due to nonsense-mediated mRNA decay. Patients with these mutations can therefore be a target for corrective gene therapy using vectors coding for full-length type XVII collagen. Proof of principle for this approach has recently been demonstrated. The analysis of naturally occurring phenomena of gene correction in the COL17A1 gene provides evidence for other mechanisms of gene correction in genetic diseases. For example, exclusion of an exon carrying a mutation can lead to a milder phenotype of nH-JEB than predicted by the original mutation. In addition, we have gained data suggesting that COL17A1 exons harbouring pathogenic mutations can also be repaired by trans-splicing, i.e. aligning corrected RNA sequences to introns in the vicinity of faulty exons in the COL17A1 premtRNA.

A novel homozygous nonsense deletion/insertion mutation in the keratin 14 gene (Y248X; 744delC/insAG) causes recessive epidermolysis bullosa simplex type Köbner.

We report the sixth case of a human keratin 14 'knockout' mutation resulting in recessive epidermolysis bullosa simplex (EBS). A novel, homozygous nonsense mutation resulting from a deletion/insertion mutation (744delC/insAG) leads to a premature termination codon in the KRT14 gene (Y248X). The patient suffers from generalized cutaneous blistering since birth, mild nail dystrophy, involvement of mucous membranes and multiple epidermolysis bullosa naevi. The clinical variability noted in K14-deficient EBS patients suggests phenotypic modulation by additional genetic and/or epigenetic factors.