Disorders of Pigmentation pdf - D. Alaa

L6 Dermatology D. Alaa

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 vitiligo. They believe that neuropeptides released from

nerve endings cause decreased melanin production

Viral theory:

cytomegalovirus DNA has been identified in skin biopsy specimen of some patients

with vitiligo, causing damage to melanocytes

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

diffuse 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. monobenzyl ether of hydroquinone is used when vitiligo

involve more than 50% of BSA and unresponsive to phototherapy

 Others: systemic anti-oxidant

Piebaldism

Autosomal dominant, cc by stable depigmented patches on anterior 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

Oculocutaneous albinism(OCA)

Autosomal recessive group of diseases characterized by diffuse pigmentary dilution due to partial
or total absence of melanin 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 philtrum

  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 upper 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

Ochronosis

There are two types;

1) Exogenous: due to prolonged 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  contributes  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
  Women 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 increases with the age of the patient
 Time interval between drug introduction and skin eruption because most of drug eruption

occurs within 1-3 weeks 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 for severe drug eruption such as  SJS/TEN

and DRESS, start systemic steroids

Clinical type

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