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Human skin melanin pigmentation is regulated by systemic and local factors. According to the type of melanin produced by melanocytes, the transfer and degradation of melanosomes differ, thus accounting for most variations between ethnicities. We made the surprising observation that in a drastically changed environment, white and black phenotypes are reversible since Caucasian skin grafted onto nude mice can become black with all black phenotypic characteristics. Black xenografts differed essentially from other grafts by the levels of epidermal FGF-2 and keratin 5. In vitro analysis confirmed that FGF-2 directly regulates keratin 5. Interestingly, this phenomenon may be involved in human pathology. Keratin 5 mutations in Dowling-Degos Disease (DDD) have already been associated with the pheomelanosome-eumelanosome transition. In a DDD patient, keratin 5 was expressed in the basal and spinous layers, as observed in black xenografts. Furthermore, in a common age-related hyperpigmentation disorder like senile lentigo (SL), keratin 5 distribution is also altered. In conclusion, modulation of keratin 5 expression and distribution either due to mutations or factors may account for the development of pigmentary disorders.

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Gastrointestinal (GI) graft-versus-host-disease (GVHD) is a common and severe complication of allogeneic hematopoietic stem cell transplantation, but clinical and histological features are unspecific. The aim of this study was to correlate the histological GI GVHD grade with the clinical outcomes. In a retrospective study of 112 patients with clinically suspected GI GVHD, colonic biopsies were reviewed by three pathologists without knowledge of the corresponding clinical data and classified in four scores, according to the NIH Consensus Project recommendations: no GVHD, possible, probable, and unequivocal GVHD. At the end of the study, the histological and clinical data were confronted with the following results: clinical diagnosis of GI GVHD was established for 70 patients (62.5%) and histological scores correlated well with the clinical diagnosis (p < 0.001) and particularly with the prognosis (p < 0.05).When severe lesions were observed, the 1 year overall survival declined to 9%. None of the features reported in the literature to support GVHD diagnosis, eosinophil count, endocrine cells aggregate, immunohistochemical analysis (cytomegalovirus, CD123, chromogranin), did not help us for diagnosis. So routine histopathology alone without immunohistochemistry is a strong and reproducible tool to diagnose GI GVHD with the help of clinical and biological information, and most importantly, histological grading proved to be a powerful prognostic value.

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BACKGROUND: Follicular vitiligo, a recently proposed new subtype of vitiligo, has primary involvement of the hair follicle melanocytic reservoir. OBJECTIVE: We sought to characterize follicular vitiligo through a case series of 8 patients. METHODS: Patients with features of follicular vitiligo who were seen at the vitiligo clinic in the National Center for Rare Skin Disorders in Bordeaux, France, were recruited. A retrospective review of case records and clinical photographs was carried out. RESULTS: There were 8 male patients with a mean age of 48 years. All patients reported significant whitening of their body and, in some, scalp hairs before cutaneous depigmentation. Examination revealed classic generalized depigmented lesions of vitiligo and an impressive presence of leukotrichia, not only in the vitiliginous areas, but also in areas with clinically normal-appearing skin. Punch biopsy specimen of the leukotrichia and vitiligo lesions demonstrated loss of melanocytes and precursors in the basal epidermis and hair follicle. LIMITATIONS: This was a cross-sectional study based on a single-center experience. CONCLUSION: Follicular vitiligo is a distinct entity within the spectrum of vitiligo. This entity may serve as the missing link between alopecia areata and vitiligo, with probable physiopathological similarities between these conditions.

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We report here an exceptional pattern of atypical lentiginous melanocytic proliferation within an adenoma, leading to focal lamina propria infiltration and pulmonary metastasis, which was considered as primary colonic mucosal melanoma (MM) in a Caucasian patient. Such case illustrates the diagnosis criteria required to differentiate primary MM from colonic metastasis of melanoma, including the absence of past history of other primary melanoma, a unique colonic and abdominal lesion with predominant features of in situ lentiginous MM and a very focal and unique invasive area without other digestive tract or abdominal localization. This tumor displayed a KIT exon 11 mutation leading to a unique combination of p.I571M and p.D572G deleterious amino acid changes. Such pattern also favors the diagnosis as KIT appears as a master oncogenic player in MM oncogenesis.

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