Disorders of Pigmentation

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L6 D erma tology D. A laa

Disorders of Pigmentation
Causes of hypopigmentation
 Infection: pityriasis versicolor
 Postinflammmatory hypopigmentation: psoroiasis , diaper rash
 Pityriasis alba: mild type of atopic dermatitis
 Hereditary diseases: piebaldism and oculocutaneous albinism( OCA )
 Chemical : rubber
 Pharmacological: topical and intralesional steroids
 Idiopathic: vitiligo
Vitiligo
It affect 0.5 -2% of general population worldwide
Average age of onset is 20 years but any age can be inflicted by this disease
Characterized by absence or decrease of melanocytes reflected by absence or decreased DOPA -
positive melanocytes
Pathogenesis
Genetic:
Environmental:
Autoimmune theory:
 Humoral immunity : association with other auto -immune diseases in particular hypo and
hyper thyroidism in addition to Addison’s , DM etc…
 Cellular immunity: T cells that infiltrate perilesional epidermis are predominantly CD8 T
cells
Intrinsic defects of melanocytes theory : They found there is a dilatation in rough endoplasmic
reticulum of melanocyes in perilesional skin
Defective free radical defense: H2O2 overproduction in lesional skin leads to oxidative damage
of melanocytes
Neural theory : especially in segmental vit iligo. They believe that neuropeptides released from
nerve endings cause decreased melanin productio n
Viral theory: cytomegalovirus DNA has been identified in skin biopsy specimen of some patients
with vitiligo, causing damage to melanocytes

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Clinical Presentation

 Present as asymptomatic, non -scaly depigmented macules and patches
 Affect mostly face (periorificial), hands, knees, elbows, ankle, nipple, anogenial
 Can present as isolated localized patch of grey or white hair (poliosis) or as premature
dif fuse graying of hair ( canities )
Classification
 Localized
 Unilateral (segmental): stop abruptly at the medline
 Acrofacial: affect extremities and face
 Generalized
Treatment
If less than 20% of BSA is affected by vitiligo:
 Topical corticosteroids : first option
 Topical immunosuppressant e.g. tacrolimus and topical pseudocatalase
 Surgery: punch graft and cultured melanocytes for vitiligo unresponsive to topical Rx
If more than 20% of BSA is affected by vitiligo :
 Narrowband UVB(311 nm): first choice
 Psoralen plus phototherapy(PUVA): psoralen can be applied topically(topical PUVA) or
oral (oral PUVA) followed by exposure to artificial UV light or natural sunlight.
 Excimer laser
 Permanent depigmentation: e.g. monobe nzyl ether of hydroquinone is used when vitiligo
involve more than 50% of BSA and unresponsive to phototherapy
 Ot hers: systemic anti -oxidant
Piebaldism
Autosomal dominant, cc by stable depigmented patches on anterio r trunk, mid extremities,
forehead and frontal scalp(white forelock), sparing the back
Present at birth
The involved skin has no melanocytes
Treatment: topical steroid and phototherapy is not effective. Auto graft from normal skin is
successful

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Oculocutaneous albinism(OCA)

Autosomal recessive group of diseases characterized by diffuse pigmentary dilution due to partial
or total absence of me lanin in skin, hair follicles and eyes despite the normal number of
melanocytes in skin
Eyes may be affected by decreased visual acuity, nystagmus and photophobia
Those patient are at increased risk for skin cancer
Treatment is photoprotection, photoprotection and photoprotection
Causes of hyperpigmentation
 Infection: Pityriasis versicolor
 Drug -induced : amiodarone, minocycline
 Postinflammatory hyperpigmentation: lichen planus and fixed drug eruption
 Erythema ab igne: net -like hyperpigmentation due to long -term exposure to heat e.g. laptop
on the thighs
 Idiopathic: melasma
Melasma
Synonyms: chloasma, mask of pregnancy
It is most prevalent among young to middle aged women
Hispanic, Asian, African or middle eastern descent are inflicted by this disease
Pathogenesis
 Exposure to UV : improvement or disappearance of lesion in winter, involvement of sun -
exposed areas and sparing of ph iltrum
 Genetic/ethnic predisposition : Mostly it is related to darker skin type
 Hormones: OCP, pregnancy (appearnace or exacerbation)
 Autoimmune thyroid diseases
Clinical features
 Brown patches on the face, but may affect extensor forearm and central upp er chest
 May lighten or disappear after delivery in light skinned women
Treatment
 Sun protection, sun protection and sun protection
 Hydroquinone (tyrosinase inhibitor). Side effects: allergic and irritant contact dermatitis,
ochronosis
 Others: Chemical peels: using salicylic acid and glycolic acid and laser

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Ochronosis

There are two types;
1) Exogenous : due to pro lo nged application of hydroquinone, and products containing
mercury, resorcinol
2) Endogenous : Autosomal recessive due to mutation in homogentisic acid oxidase.
Macular amyloidosis
 Pruritic confluent or rippled hyperpigmented macules and patches
 Mostly involve upper back and forearms
 Women affected more than men
 local friction from nylon brushes, towels and other rough materials contrib utes to the
production of this disease
 Treatment : breaking itch -scratch cycle , stopping friction e.g. brush use addition to use of
topical steroids plus keratolytics

Drug Reactions

Epidemiology
 The skin is one of the most common targets for adverse drug reactions
 W omen are more susceptible than men
 Paradoxically, the incidence of most immunologically mediated drug eruptions is increased
in the setting of immunosuppression; for example, in patients with AIDS
 The incidence of adverse reactions also in creases with the age of the patient
 Time interval between drug introduction and skin eruption because most of drug eruption
occurs within 1 -3 w eeks after initiation of new
Treatment
1. Withdrawal of suspect drug as soon as possible
2. If many drugs are incriminated, stop all non -essential drugs
3. If the suspect drug is essential, substitute with another that does not cross -react
4. For mild drug eruption, start topical steroid and f or severe drug eruption such as SJS/TEN
and DRESS , start systemic steroids
Clinical type

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Note :

 Stevens -Johnson syndrome : if less than 10% of body surface area is involved
 Toxic epidermal necrolysis when more than 30% of body surface area is involved

Mubark A. Wilkins