1. Disorder of Skin Pigmentation

2. 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.

3. 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

4. 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 .

5. 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 .

6. 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 .

7. 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 .

8. 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) .

9. 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 .

10. 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 .

11. 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 .

12. 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 .

13. 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 .

14. 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 .

22. 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 .

24. 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 .

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

27. 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 .

30. 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 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 .

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