Sofie De Schepper

Germline loss-of-function mutations in SPRED1 cause a neurofibromatosis 1-like phenotype

We report germline loss-of-function mutations in SPRED1 in a newly identified autosomal dominant human disorder. SPRED1 is a member of the SPROUTY/SPRED family of proteins that act as negative regulators of RAS->RAF interaction and mitogen-activated protein kinase (MAPK) signaling. The clinical features of the reported disorder resemble those of neurofibromatosis type 1 and consist of multiple café-au-lait spots, axillary freckling and macrocephaly. Melanocytes from a café-au-lait spot showed, in addition to the germline SPRED1 mutation, an acquired somatic mutation in the wild-type SPRED1 allele, indicating that complete SPRED1 inactivation is needed to generate a café-au-lait spot in this syndrome. This disorder is yet another member of the recently characterized group of phenotypically overlapping syndromes caused by mutations in the genes encoding key components of the RAS-MAPK pathway. To our knowledge, this is the first report of mutations in the SPRY (SPROUTY)/SPRED family of genes in human disease.

Molecular Dissection of Isolated Disease Features in Mosaic Neurofibromatosis Type 1

Elucidation of the biological framework underlying the development of neurofibromatosis type 1 (NF1)-related symptoms has proved to be difficult. Complicating factors include the large size of the NF1 gene, the presence of several NF1 pseudogenes, the complex interactions between cell types, and the NF1-haploinsufficient state of all cells in the body. Here, we investigate three patients with distinct NF1-associated clinical manifestations (neurofibromas only, pigmentary changes only, and association of both symptoms). For each patient, various tissues and cell types were tested with comprehensive and quantitative assays capable of detecting low-percentage NF1 mutations. This approach confirmed the biallelic NF1 inactivation in Schwann cells in neurofibromas and, for the first time, demonstrated biallelic NF1 inactivation in melanocytes in NF1-related cafe-au-lait macules. Interestingly, both disease features arise even within a background of predominantly NF1 wild-type cells. Together, the data provide molecular evidence that (1) the distinct clinical picture of the patients is due to mosaicism for the NF1 mutation and (2) the mosaic phenotype reflects the embryonic timing and, accordingly, the neural crest-derived cell type involved in the somatic NF1 mutation. The study of the affected cell types provides important insight into developmental concepts underlying particular NF1-related disease features and opens avenues for improved diagnosis and genetic counseling of individuals with mosaic NF1.

First histopathological and immunophenotypic analysis of early dynamic events in a patient with segmental vitiligo associated with halo nevi

Segmental vitiligo is often ascribed to the neurogenic theory of melanocyte destruction, although data about the initial etiopathological events are scarce. Clinical, histopathological and T‐cell phenotypic analyses were performed during the early onset of a segmental vitiligo lesion in a patient with associated halo nevi. Histopathological analysis revealed a lymphocytic infiltrate, mainly composed of CD8+ T‐cells and some CD4+ T‐cells around the dermo–epidermal junction. Flow cytometry analysis of resident T‐cells revealed a clear enrichment of pro‐inflammatory IFN‐γ producing CD8+ T‐cells in lesional skin compared to the non‐lesional skin. Using human leukocyte antigen‐peptide tetramers (MART‐1, tyrosinase, gp100), increased numbers of T cells, recognizing melanocyte antigens were found in segmental vitiligo lesional skin, as compared with the non‐lesional skin and the blood. Our findings indicate that a CD8+ melanocyte specific T cell‐mediated immune response, as observed in generalized vitiligo, also plays a role in segmental vitiligo with associated halo nevi.

Somatic loss of wild type NF1 allele in neurofibromas: Comparison of NF1 microdeletion and non-microdeletion patients.

Neurofibromatosis type I (NF1) is an autosomal dominant familial tumor syndrome characterized by the presence of multiple benign neurofibromas. In 95% of NF1 individuals, a mutation is found in the NF1 gene, and in 5% of the patients, the germline mutation consists of a microdeletion that includes the NF1 gene and several flanking genes. We studied the frequency of loss of heterozygosity (LOH) in the NF1 region as a mechanism of somatic NF1 inactivation in neurofibromas from NF1 patients with and without a microdeletion. There was a statistically significant difference between these two patient groups in the proportion of neurofibromas with LOH. None of the 40 neurofibromas from six different NF1 microdeletion patients showed LOH, whereas LOH was observed in 6/28 neurofibromas from five patients with an intragenic NF1 mutation (P = 0.0034, Fishers exact). LOH of the NF1 microdeletion region in NF1 microdeletion patients would de facto lead to a nullizygous state of the genes located in the deletion region and might be lethal. The mechanisms leading to LOH were further analyzed in six neurofibromas. In two out of six neurofibromas, a chromosomal microdeletion was found; in three, a mitotic recombination was responsible for the observed LOH; and in one, a chromosome loss with reduplication was present. These data show an important difference in the mechanisms of second hit formation in the 2 NF1 patient groups. We conclude that NF1 is a familial tumor syndrome in which the type of germline mutation influences the type of second hit in the tumors.

Café-au-lait spots in neurofibromatosis type 1 and in healthy control individuals: hyperpigmentation of a different kind?

Solitary café-au-lait spots are quite common in the general population but multiple café-au-lait macules (CALM) are often indicative of an underlying genetic disorder. The frequency of having more than five CALM is rare in normal individuals and is therefore considered as a cut-off for the diagnosis of neurofibromatosis type 1 (NF1). The etiopathogenesis of these macules is still very obscure. In this study we compared epidermal melanocyte and dermal mast cell numbers between four groups: control normal and control CALM skin, and NF1 normal and NF1 CALM skin and elaborated a possible role for stem cell factor (SCF) in CALM formation. The groups were analyzed by immunohistochemistry for numerical analysis of the melanocyte and mast cell population and by ELISA, western blot analysis and real-time quantitative PCR for further determination of the role of SCF. We found a significant increase in melanocyte density in NF1 CALM skin compared with the isolated CALM in control individuals. However, both groups displayed a similar increase in mast cell density. In addition, we found increased levels of soluble SCF in NF1 CALM and in NF1 normal fibroblast supernatant. We conclude that SCF is an important cytokine in NF1 skin, but that additional (growth) factors and/or genetic mechanisms are needed to induce NF1-specific CALM hyperpigmentation.

In vivo vitiligo induction and therapy model: double-blind, randomized clinical trial.

In this study, we developed an in vivo vitiligo induction model to explore the underlying mechanisms leading to Koebner’s phenomenon and to evaluate the efficacy of therapeutic strategies. The model consisted of 12 pigmented test regions on the back of generalized vitiligo patients that were exposed to three Koebner induction methods: cryotherapy, 755 nm laser therapy, and epidermal abrasion. In addition, four cream treatments (pimecrolimus, tacrolimus, steroid and placebo) were randomly applied. Koebnerization was efficiently induced by all three induction methods. In general, cryotherapy was the best method of Koebner induction, followed by 755 nm laser therapy and epidermal abrasion. Reproducible results were obtained, which showed enhanced depigmented surface areas and higher amounts of T lymphocytes in placebo‐treated test zones compared to active treated areas. Tacrolimus and local steroids were better inhibitors of Koebner’s process (P < 0.05) compared to pimecrolimus. Our in vivo vitiligo induction model is very informative to investigate vitiligo induction and to determine the efficacy of topical treatments in vitiligo. This proof of concept confirms the efficient comparison of head‐to‐head therapeutic strategies intra‐individually in a standardized, specific and better timed way.

NF1 loss induces senescence during human melanocyte differentiation in an iPSC-based model.

Neurofibromatosis type 1 (NF1) is a frequent genetic disease leading to the development of Schwann cell‐derived neurofibromas or melanocytic lesions called café‐au‐lait macules (CALMs). The molecular mechanisms involved in CALMs formation remain largely unknown. In this report, we show for the first time pathophysiological mechanisms of abnormal melanocyte differentiation in a human NF1+/−‐induced pluripotent stem cell (iPSC)‐based model. We demonstrate that NF1 patient‐derived fibroblasts can be successfully reprogrammed in NF1+/− iPSCs with active RAS signaling and that NF1 loss induces senescence during melanocyte differentiation as well as in patients‐derived CALMs, revealing a new role for NF1 in the melanocyte lineage.

Total-Body Examination vs Lesion-Directed Skin Cancer Screening.

IMPORTANCE Skin cancer is the most frequent cancer type. It remains unknown if and how screening programs can be organized in a cost-effective manner. OBJECTIVE To compare the 2 screening strategies of systematic total-body examination (TBE) and lesion-directed screening (LDS), with a focus on the participation rate, detection rate, anxiety, and cost. DESIGN, SETTING, AND PARTICIPANTS Population-based cross-sectional screenings by a team of 6 dermatologists were organized in 2 sociodemographically similar regions. The TBE was organized in a community of 9325 inhabitants 18 years and older (Wichelen, East Flanders, Belgium) during a 5-day screening (March 14-18, 2014). The LDS was organized in a sociodemographically comparable community (Nevele, East Flanders, Belgium) of 9484 adult inhabitants during a 4-day screening (April 22 and 25-27, 2014). The first population received a personal invitation for a standard TBE. In the second population, individuals were invited for an LDS if they had a lesion meeting 1 or more of the following criteria: ABCD rule (A, asymmetry; B, borders; C, colors; and D, differential structures), ugly duckling sign, new lesion lasting longer than 4 weeks, or red nonhealing lesions. MAIN OUTCOMES AND MEASURES In total, 1982 individuals were screened, and 47 skin cancers (2.4%) were histologically confirmed, including 9 melanomas (0.5%), 37 basal cell carcinomas (1.9%), and 1 squamous cell carcinoma or Bowen disease (0.1%). RESULTS The positive predictive value for all suspicious lesions was 56.6% (47 of 83). The participation rate was 17.9% (1668 of 9325) in the TBE group vs 3.3% (314 of 9484) in the LDS group (P < .01). The skin cancer detection rate per 100 participants did not differ significantly between the 2 groups, with rates of 2.3% (39 of 1668) in the TBE group vs 3.2% (8 of 248) in the LDS group (P = .40). The operational effectiveness per 100 invitees was 0.4% (39 of 9325) in the TBE group vs 0.1% (8 of 9484) in the LDS group (P < .01). In addition, LDS was 5.6 times less time consuming than TBE. Participants in the LDS group had significantly higher baseline anxiety levels compared with participants in the TBE group (3.7 vs 3.3 points on a visual analog scale, P < .01). In screenees without a suspicious lesion, anxiety levels significantly dropped after screening. CONCLUSIONS AND RELEVANCE Total-body examination yielded a higher absolute number of skin cancers. Lesion-directed screening had a similar detection rate of 3.2% (8 of 248) but was 5.6 times less time consuming. When performed by dermatologists, LDS is an acceptable alternative screening method in health care systems with limited budgets or long waiting lists.

Seborrheic keratosis with basal clear cells: a peculiar microscopic mimic of melanoma in situ

To the Editor, Seborrheic keratoses are among the most common neoplasms seen in the daily practice in dermatopathology. In 2006, Neuhaus et al.1 described nine cases of seborrheic keratosis with linear basal clear cells mimicking melanoma in situ in conventional sections. Recently, we identified a similar case on the leg of a 64-year-old woman. Histopathologically, the lesion exhibited the typical architectural pattern of a seborrheic keratosis of the hyperkeratotic type, with acanthosis, papillomatosis and hyperkeratosis. Along the basal layer a striking row of clear cells was seen (Fig. 1). The cells showed a small nucleus that was displaced upwards in many cells and had abundant clear cytoplasm. No nests were seen. This peculiar finding raised the possibility of a melanoma in situ colonizing a seborrheic keratosis. However, the cells failed to react with S100 protein and Melan-A. At first glance, a high molecular weight keratin immunostain appeared to be negative. Only by closer inspection could clear-cut peripheral positivity be seen. Interestingly, seven of the nine original cases of Neuhaus et al.1 revealed the same membranous keratin positivity seen in our case. In contrast, two of their cases showed a diffuse strong keratin immunopositivity of the basal clear cells. A similar peculiar positive reaction was found for basal cell keratins CK5 (Fig. 2) and CK14. CK7 was negative in these cells. This cytokeratin profile is distinct from what is expected in association with both pagetoid Bowen’s disease and extramammary Paget’s disease, which can additionally be distinguished by the presence of an irregular nested intraepidermal tumor cell pattern rather than a linear basal arrangement. Furthermore, primary extramammary A

Hypomelanoses in Children

Hypomelanosis of the skin is a frequently encountered problem in childhood, being totally innocent or representing the first sign of a multisystem disorder. Medical history, clinical examination, Wood’s light investigation, histological analysis of the skin and a multidisciplinary consultation can contribute to a correct and early diagnosis of the different types of hypopigmentations. In the present paper, we present a systematic clinical approach to the differential diagnosis of those skin disorders.