Nonsegmental vitiligo follows Blaschko's lines and embryonic pigmentary segments.

BACKGROUND: Pathogenic mechanism that determines the localization of vitiligo patches and thus a patterned distribution in patients with nonsegmental vitiligo has remained poorly elucidated. A distributional similarity of the vitiligo patches with Blaschko's lines has been documented in patients with segmental vitiligo, both isolated segmental vitiligo and mixed vitiligo but never in cases of nonsegmental vitiligo. METHODS: Distribution of nonsegmental vitiligo patches on face and neck regions was assessed and compared with Blaschko's lines and also with embryonic pigmentary segments on the face. RESULTS: This study has documented distributional similarity of the nonsegmental vitiligo patches on face and neck with Blaschko's lines and the "embryonic pigmentary segments" among 154 (58.6%) cases. Patches around the palpebral and other fissures like periorbital, perinasal, perioral, and periaural were more common. In addition to the vitiligo patches, the spared areas were also found to respect the embryonic segmental outlines and follow the Blaschko's lines. CONCLUSION: Distributional pattern of the individual nonsegmental vitiligo patches along the Blaschko's lines and embryonic pigmentary segments suggests that mosaicism might control the susceptibility to the disease process in a patterned manner. LIMITATION: No genetic testing could be performed to confirm the hypothesis. Evaluation of nonsegmental vitiligo was done only on the face and neck areas.

Histopathological comparison of lesional and perilesional skin in melasma: A cross-sectional analysis.

BACKGROUND: Melasma is a common acquired hyperpigmentary disorder of the sun exposed skin, especially the face. The pathogenesis is unclear but interplay between genetic factors, hormones and ultraviolet radiation is important. We have evaluated the histological characteristics of melasma and compared the findings with adjacent normal skin. METHODS: Skin biopsies were taken from both melasma and the surrounding perilesional normal skin in 50 Indian women. The sections were stained with hematoxylin and eosin, Fontana-Masson and Verhoeff-Van Gieson stains. RESULTS: Biopsy from melasma showed significant epidermal atrophy, basal cell hyperpigmentation and solar elastosis when compared with the perilesional skin. We found that the proportion of pendulous melanocytes was significantly higher in the lesional biopsy compared with the perilesional biopsy (76% vs 42%, P < 0.001). Similarly, pigmentary incontinence and features of solar elastosis were significantly higher in the lesional skin compared with the perilesional skin. CONCLUSION: The characteristic histopathological features such as epidermal atrophy, basal cell hyperpigmentation and solar elastosis suggest the role of chronic sun exposure in the pathogenesis of melasma. Presence of pendulous melanocytes is a characteristic feature of melasma. The presence of pendulous melanocytes may have prognostic implications in melasma.

A morphometric and immunohistochemical study of melanocytes in periorbital hyperpigmentation.

BACKGROUND: An increase in number of melanocytes in the basal cell layer of the epidermis is an important feature in many disorders of hyperpigmentation. In this study, we attempted an objective evaluation of the linear density of melanocytes and keratinocytes, along with other epidermal characteristics, in periorbital hyperpigmentation using immunohistochemistry and morphometric techniques. METHODS: Melanocytes and epidermal parameters were assessed by digital morphometry in 30 newly diagnosed cases of periorbital hyperpigmentation and 14 controls from the post-auricular region. Melanocytes were labelled with the immunohistochemical stains, Melan-A and tyrosinase. We studied the linear keratinocyte density, mean linear melanocyte density, ratio of melanocytes to keratinocytes, the ratio between inner and outer epidermal length, maximum epidermal thickness and minimum epidermal thickness. RESULTS: Melan-A expression of melanocytes showed strong positive correlation (r=0.883) with the tyrosinase expression. Mean linear melanocyte density was 24/mm (range: 13-30/mm) in cases and 17/mm (13-21/mm) in controls and this difference was statistically significant (P<0.001). The mean ratio of melanocyte to keratinocyte was 0.22 (0.12-0.29) in cases and 0.16 (0.12-0.21) in controls; again, this difference was statistically significant (P<0.001). There was a mild negative correlation with linear keratinocyte density (r=-0.302) and the ratio between inner and outer epidermal length (r=-0.456). However, there were no differences in epidermal thicknesses. LIMITATIONS: There were fewer control biopsies than optimal, and they were not taken from the uninvolved periorbital region. CONCLUSION: Mean linear melanocyte density and the ratio of melanocytes to keratinocytes is increased in cases with periorbital hyperpigmentation. It is, therefore, likely that increased melanocyte density may be the key factor in the pathogenesis of periorbital hyperpigmentation.

Follicular mucinosis: an important differential diagnosis of leprosy in an endemic area.

Primary follicular mucinosis is a rare dermatosis characterized by the accumulation of mucin in the follicular epithelium and sebaceous glands. Clinically, it is characterized by the presence of papules or well-circumscribed and infiltrated plaques. In this paper, we report the case of a female patient, seven years old, evolving for three months with an asymptomatic, erythematous and infiltrated plaque located in the chin region. The research of thermal, pain and tactile sensitivity was inconclusive. Histological findings confirmed the diagnosis of follicular mucinosis. There was regression of the lesion with the use of medium potency topical corticosteroids for 20 days. The pathogenesis of follicular mucinosis remains unknown, being in some cases associated with lymphoproliferative disorders. In endemic areas of leprosy, isolated and infiltrated follicular mucinosis lesions should be further differentiated from leprosy.

Follicular mucinosis: an important differential diagnosis of leprosy in an endemic area

Primary follicular mucinosis is a rare dermatosis characterized by the accumulation of mucin in the follicular epithelium and sebaceous glands. Clinically, it is characterized by the presence of papules or well-circumscribed and infiltrated plaques. In this paper, we report the case of a female patient, seven years old, evolving for three months with an asymptomatic, erythematous and infiltrated plaque located in the chin region. The research of thermal, pain and tactile sensitivity was inconclusive. Histological findings confirmed the diagnosis of follicular mucinosis. There was regression of the lesion with the use of medium potency topical corticosteroids for 20 days. The pathogenesis of follicular mucinosis remains unknown, being in some cases associated with lymphoproliferative disorders. In endemic areas of leprosy, isolated and infiltrated follicular mucinosis lesions should be further differentiated from leprosy.