الفهرس 
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Abstract
Vitiligo is an acquired depigmenting disorder characterized by the loss of melanocytes from the epidermis and it affected between 1% and 2% of the general population without any racial, sexual or
regional differences. Vitiliginous patches contain either reduced
melanin or no pigment at all. The patches are initially small but they
progressively enlarge and coalesce into larger patches.
The pathogenesis of vitiligo is attributable to many hypotheses
that have been proposed to explain the destruction of melanocytes,
including neurogenic theory, the self-destructive theory and the
autoimmune theory.
Stressed cells are characterized by elevated expression of stress
proteins. Stress proteins include the heat shock protein (Hsp) family
which is upregulated in response to elevated environmental
temperatures and other forms of stresses. Stress proteins are
immunogenic and were shown to serve as antigens in certain
autoimmune diseases. Stress proteins also enhance an immune
response by inducing phagocytosis and processing of chaperoned
antigens by dendritic cells.
The objective of this study was to investigate Hsp70 expression
in skin of normal individuals compared to vitiligo patients and to
correlate this expression with the clinicopathological parameters of the
latter group, to explore the possible role of Hsp70 in the pathogenesis
of this disease. This study was carried out on thirty two patients with
vitiligo and ten healthy volunteers as controls. Skin biopsies were
taken; histopathological evaluation using hematoxylin and eosin
staining, and immunohistochemical evaluation of Hsp 70 using mouse
monocolonal antibody were performed.
Histopathological examination of the vitiliginous biopsies
revealed many changes such as keratinocytes vacuolization, basement
membrane thickening and dermal perivascular inflammatory infiltrate.
Complete absence of melanin was observed in most of the cases
(65.6%). Perilesional skin showed also some features that precede
the occurrence of vitiligo like keratinocytes vacuolization, and
presence of dermal inflammation but they retain significant amount of
melanin.
As regards, Hsp70 expression, all normal skin showed
positivity for Hsp70 with cytoplasmic localization while 96.9% of
vitiligo cases showed Hsp70 expression with nucleocytoplasmic
pattern in 64.5% of cases and cytoplasmic pattern in 35.5% of cases.
The percentage of Hsp 70 expression in vitiliginous skin ranged
between 0 –100, with a mean of 68.59±29.27 and a median of 75
while H score of Hsp 70 expression in those lesions ranged between 0
and 300 with a mean of 158.28±89.96 and a median of 150.
Vitiligo skin showed more intense expression compared to
control skin (p<0.001). Nucleocytoplasmic pattern was only seen in
vitiligo skin in comparison with normal skin that showed cytoplasmic
pattern only (p<0.001). The median value of percentage (p<0.001)
and H score of Hsp70 expression (p<0.001) were higher in vitiligo
skin compared to normal skin.
Nucleocytoplasmic pattern of Hsp70 tended to be associated
with progressive increase in severity of disease assessed by VIDA
score (p=0.07). The median value of Hsp70 percentage of expression
tended to be higher in patients with short disease duration in
comparison with those with prolonged diseases (p=0.08)
Hsp70 was studied in the three perilesional biopsies which
revealed positive expression with a cytoplasmic pattern in 2 cases and
nucleocytoplasmic pattern in one case. It was expressed in a mild
intensites in 2 cases (66.7%) and strong intensity in one case (33.3%).
The percentage of Hsp 70 expression in perilesional biopsy
ranged between 10 – 90, with a mean of 36.66± 46.18 and a median
of 10.0 while H score of Hsp 70 expression ranged between10 and
270 with a mean of 96.66 ±150.11and a median of 10.
Hsp70 was also reported to be increased in other skin diseases
compared to normal skin such as psoriasis suggesting its role in the
pathogenesis of psoriasis Hsp70 was also described to be expressed in
lichen planus and systemic sclerosis.
from the present study, up-regulation of heat shock protein 70,
in the form of its intense and diffuse expression may be blamed in
pathogenesis of vitiligo. Nuclear localization of heat shock protein 70
may be more important than its presence or absence, beside it may be
related to progression of the disease.