Disorder of Skin Pigmentation

Disorder of Skin Pigmentation Normal 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 rays

Hyper pigmentation Causes of hyper pigmentation :- Genetic :- freckles , lentigens , Mongolian spot , Becker nevus , café au lait macule , acanthosis nigrican . Metabolic :- heamchromatosis , amyloidosis , wilson disease , primary biliary cirrhosis . Endocrine :- addison`s disease , acromegaly , cushing syndrome , hyperthyroidism , pregnancy , menstruation , oral contraceptive , melasma , pheochromocytoma , ACTH therapy , ACTH & MSH secreting tumors .

Hyper pigmentation Nutritional :- 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 .

Melasma (chloasma , mask of pregnancy) Is an acquired brown hyper pigmentation involving the face in genetically predisposed women . The pigmentation may develop slowly without signs of inflammation & may be faint or dark . There is increased number & activity of melanocytes in the epidermis & an increase number of melanophage in the dermis . The forehead , malar eminences , upper lip , & chin are most frequently affected . The light brown color becomes darker after exposure to sun , during pregnancy , or when taking oral contraceptives .

Melasma Treatment :- is unsatisfactory , treatment may be in the form Sunscreen . Bleaching agents that contain hydroquinone . Topical tretinoin 0.1% . Topical steroid .

Freckles Are small light brown macules that are promoted by sun exposure & fade during winter months . They are usually confined to the face , arms , & back . The number varies . They occur as an autosomal dominant trait & are most often found in individuals with fair complexions . The use of sunscreen prevents the appearance of new freckles & helps prevent the darkening of existing freckles that typically accompanies sun exposure .

Lentigens Is a small tan , brown , or black oval-rounded macule with irregular outline that is darker than a freckle & is not affected by sunlight . The lesions vary in size from 0.2-2 cm . Simple lentigens arise most often in childhood as a few scattered lesions , often on areas not exposed to sun , including mucous membrane . Senile or solar lentigens are common after middle age on the face & back of the hands . In contrast to freckles , lentigens have increased number of melanocytes .

Lentigens Differential diagnosis :- Treatment :- Freckles . Junctional melanocytic nevi . Lentigo malignant melanoma . Treatment :- Cryotherapy , laser , topical tretinoin 0.1% cream , bleaching agent (hydroquinone cream) .