Disorder of Skin Pigmentation
Disorder of Skin PigmentationNormal skin pigmentation is an admixture of the following : red (oxyhemoglobin) , blue (deoxyhemoglobin) , yellow-orange (carotene) , & brown (melanin) , but melanin is the major component of skin color . Two types of normal melanin pigmentation are the basis for normal skin color . Constitutive skin color is the genetically determined color of healthy skin unaffected by solar irradiation . Facultative skin color is the skin color that results from an increase in the intensity of skin color as a result of UVR exposure.
Disorder of Skin Pigmentation
Melanocyte is the sole site of melanin formation located between the basal cells of epidermis . Melanin is synthesized within melanosome of melanocytes from tyrosin by the action of tyrosinase enzyme . Two types of melanin have been demonstrated ; eomelanin which is responsible for brown-black color pheomelanin which is responsible for yellow-red color . Melanin has a primary physiologic role in protection of the skin . This is related to the absorption characteristic of melanin both in the UV & visible raysHyper pigmentation
Hyper pigmentationNutritional :- kwashiorkor , pellagra , vitamin A deficiency , B12 & folate deficiency , malabsorption syndrome ( chronic nutritional deficiency) . Inflammatory & post inflammatory :- chronic infection (TB , malaria , kalazar , schistosomiasis , later stage of sub acute bacterial endocarditis) , lichen simplex chronicus , lichen planus , DLE , psoriasis , lupus erythematosus , atopic dermatitis , tinea versicolor . Chemicals :- arsenic , bleomycin , cyclophosphamide , 5FU , nitrogen mustard , tars , phototoxic agents , berloque dermatitis . Physical :- radiation (ionizing , thermal , UV) , trauma Neoplastic :- melanoma , non Hodgkin lymphoma , internal malignancy .
Hypo pigmentation
Causes of hypo pigmentation :- Genetic:- circumscribed e.g. nevus depigmentosus , tuberous sclerosis diffuse e.g. albinism , phenylketonurea . Endocrine :- hypo pituitrism , hyperthyroidism . Inflammatory & post inflammatory :- pityriasis alba , psoriasis , cryotherapy , tinea versicolor , DLE , morphea , leprosy , post kalazar . Chemical :- antimalarial , arsenic , azelaic acid , hydroquinone , tretinoin , monobenzyle ether of hydroquinone , glucocortcoid .Hypo pigmentation
Nutritional :- mal absorption syndrome (chronic protein deficiency) , pernicious anemia , kwashiorkor , vitamin B12 deficiency . Physical :- burn (thermal , ionizing , UV) , trauma , post laser , post dermabrasion . Un classified :- vitiligo , idiopathic guttate hypo melanosis .Vitiligo
Vitiligo :- is an acquired loss of skin pigmentation , characterized by well-circumscribed milky-white cutaneous macule devoid of identifiable melanocytes . Incidence :- Affecting up to 1-2% of the population . Both gender are equally affected . Any age could be affected (congenital vitiligo is very rare) .
Vitiligo
Etiology :- is unknown , there appears to be a certain genetic predisposition & a number of potential precipitating factors . Heritability :- 30% of patients have family history (segmental vitiligo appears not to be familial) . Precipitating factors :- most of the patients attribute the onset of their disease to specific life event or crises or illness , physical injury . Koebner phenomenon is +ve in at least one third of patients . Histology :- there is complete absence of melanocytes . Usually there is no inflammatory component .Vitiligo
Clinical feature :- Typical macule of vitiligo has a chalky or milk-white color ,rounded to oval in shape . varies in size from few cm. to several cm. in diameter , & lacks other epidermal changes . Number varies from single to hundreds . Mucosal involvement is not infrequent ; the genitalia , nipples , lips , & gingiva may be involved . Other cutaneous abnormalities : vitiligo may be associated with leukotrichia , prematurely gray hair , halo nevi , & alopecia areata . Systemic disease association : associated with other autoimmune disease .Vitiligo
Types of vitiligo :- Focal vitiligo :- any site could be affected . Segmental vitiligo (dermatomal) :- this form is treatment resistant & earlier onset . Acrofacial vitiligo :- affecting distal fingers & the facial orifices . Generalized vitiligo :-involvement is symmetrical , the most common sites are face , upper part of the chest , dorsal aspects of the hands , axillae , groin . There is tendency for the skin around orifices to be affected . Universal vitiligo .Vitiligo
Differential diagnosis :- Chemical leukoderma . Leprosy . Lupus erythematosus . Pityriasis alba . Tinea versicolor . Nevus depigmentosus . Post inflammatory hypo melanosis . Idiopathic guttate hypo melanosis . Natural course :- is unpredictable . Spontaneous repigmentation occurs in no more than 15-25% of cases .Treatment :- reassurance Sunscreen . Cosmetics :- conventional makeup , dyes , & self tanning preparations . Topical glucocorticoids :- potent or very potent topical steroid for 1-2 months . Topical PUVA :-is the application of diluted solution of 8-methoxypsoralin followed by UVA . used when vitiligo is up to 5% Topical immunomodulating agents:- tacrolimus and pimcrolimus Oral PUVA :- is the most practical effective treatment for affected patients who are over the age of ten , who have wide spread vitiligo .
Vitiligo
Surgical methods :- autologous skin grafts ( minigraft & suction blister grafting) . Transplantation of cultured autologous melanocytes. The use of these technique may be limited by cost , & the development of vitiligo ( koebner phenomenon) at the donor sites . 7. Total depigmentation :- if more than 50% of the body surface area is affected by vitiligo , the patient can consider depigmentation . Monobenzen (monobenzyl ether of hydroquinone) 20% is applied twice daily for 3-6 months to residual pigmented areas .Albinism
Albinism :- is an uncommon disorder . There are number of distinct genetic types which are inherited as autosomal recessive . In the two main types , tyrosinase +ve & tyrosinase –ve , there is a diffuse dilution of normal pigmentation of the skin , hair , fundus oculi & iris . The whole skin is white & pigment is also lacking in the hair , iris & retina . Albino have poor sight , photophobia & a rotatory nystagmus . As they grow older tyrosinase +ve albinos gain a little pigment in their skin , iris & hair .Patient with this disorder are photosensitive , & sequamous- & basal cell carcinoma develop in the sun exposed areas of the skin .these patients show therefore use an effective screen .