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.

Morphometric study of microvessels, epidermal characteristics and inflammation in psoriasis vulgaris with their correlations.

BACKGROUND: Vascular proliferation, inflammation and epidermal changes are important features in the pathogenesis of psoriasis. AIMS: In this study we attempted an objective evaluation of these parameters using morphometry. METHODS: Inflammation, microvessels and epidermal parameters were assessed in 50 newly diagnosed cases of psoriasis vulgaris (between 01 Nov 2008 and 31 Oct 2011) by morphometry. Parameters studied were microvessel density, microvessel caliber, inflammatory cell density in dermis, ratio between inner and outer epidermal length, maximum epidermal thickness, minimum epidermal thickness and difference between maximum epidermal thickness and minimum epidermal thickness. RESULTS: Microvessel caliber showed moderate correlation (r = 0.645) and microvessel density, weak correlation (r = 0.226) with inflammatory cell density in dermis. Both these parameters also showed mild positive correlation with "ratio between inner and outer epidermal length". All parameters except minimum epidermal thickness showed mild positive correlation with inflammatory cell density in dermis. CONCLUSION: All microvessels and epidermal parameters showed positive correlation with dermal inflammation; and epidermal parameters exhibited positive correlation with micro-vascular dilation. It is likely that inflammation is a key factor in the pathogenesis of psoriasis.