Derma sce dr .lana

9. Inherited dyschromatoses Dyschromatoses are disorders characterized by both hyperpigmented and hypopigmented macules. A. Dyschromatosis symmetrica hereditaria (DSH) Also known as reticulate acropigmentation of Dohi. Characterized by hyperpigmented and hypopigmented macules, classically in a symmetrical acral distribution. The chapter describes increased melanin in basal keratinocytes in hyperpigmented macules and reduced density of DOPA-positive melanocytes in hypopigmented macules. Mutations in the RNA-specific adenosine deaminase gene (ADAR, historically DSRAD) are associated with the condition. Treatment is unsatisfactory; strict sun avoidance may reduce the contrast between lesions. B. Dyschromatosis universalis hereditaria (DUH) Rare disorder with generalized hypo- and hyperpigmented macules. Usually begins in early childhood. Most reported patients in the chapter are Japanese, although cases have been reported in other populations. Autosomal dominant forms are associated with mutations in ABCB6; SASH1 mutations can also cause DUH. Histology shows focal increases or decreases in melanin in the basal epidermis in hyperpigmented and hypopigmented areas, respectively. Treatment: No satisfactory treatment is available. C. Important differential diagnosis Xeroderma pigmentosum: May produce hyper- and hypopigmented macules in childhood, but the lesions show a photodistribution and are associated with premature actinic damage. DSH: Predominantly acral and symmetrical. DUH: More generalized distribution, usually with early-childhood onset. Final exam trap: Both DSH and DUH feature hyperpigmented and hypopigmented macules, but DSH is predominantly acral and symmetrical, whereas DUH is generalized.

Exam trap: DKC is associated with shortened telomeres and nail abnormalities/leukoplakia; FA is associated with chromosomal breakage and congenital radial-ray abnormalities. Both require attention to hematologic complications and malignancy risk.

Exam pearl: Arsenic hyperpigmentation is especially important because pigmentation may precede palmoplantar keratoses and squamous cell carcinoma by years.

6. Exogenous ochronosis and tinea versicolor A. Exogenous ochronosis Cause: Associated with topical hydroquinone use. Clinical clue: Persistent blue–black or blue-gray pigmentation, often involving treated areas. Histopathology: Yellow–brown, banana-shaped fibers in the papillary dermis. Exam trap: Do not confuse exogenous ochronosis with ordinary melasma or PIH, particularly in a patient with prolonged hydroquinone use. B. Tinea (pityriasis) versicolor Cause: Superficial infection by Malassezia globosa and other Malassezia species. Clinical features: Hypo- or hyperpigmented macules, or very thin papules and plaques with fine scale. Distribution: Usually upper trunk and proximal upper extremities; may involve the neck, face, and groin. Lesions may coalesce centrally. Investigation: KOH preparation of scale shows both hyphal and yeast forms of Malassezia. Differential diagnosis: PIH and confluent and reticulated papillomatosis. Exam trap: Fine scale and a positive KOH preparation help distinguish tinea versicolor from other causes of hyperpigmentation.

4. Melasma patterns and limitations of Wood's lamp examination The three classic clinical patterns Centrofacial — most common: Forehead, cheeks, nose, upper lip, and chin; the philtrum and nasolabial folds are relatively spared. Malar: Cheeks and nose. Mandibular: Along the jawline. Less common sites include the extensor forearms and mid-upper chest. Classification by pigment location Epidermal Dermal Mixed Indeterminate Wood's lamp limitation In theory, epidermal pigment becomes more prominent and dermal pigment less obvious under Wood's lamp examination. However, clinicopathologic studies found that Wood's lamp findings do not reliably correlate with histology. Exam trap: Do not use Wood's lamp findings alone to determine the histologic depth of melasma.

3. Histopathology and disease mechanisms A. PIH Epidermal PIH: Increased melanin production and/or transfer to keratinocytes. Dermal PIH: Damage to the basement membrane allows melanin to enter the dermis, where macrophages phagocytose it, forming melanophages. B. Melasma Increased melanin deposition in all epidermal layers, particularly the basal layer. Melanocytes are normal to slightly increased in number, enlarged, and have prominent dendrites. Increased melanosomes are present in lesional melanocytes. UV exposure and hormonal factors are important; hyperfunctional melanocytes are thought to increase melanin production. C. EDP Characterized clinically by ashy-gray macules and patches. Histologic and clinical overlap exists with LPP, PIH, and pigmented contact dermatitis. Early lesions may have a thin, raised erythematous border. The chapter emphasizes the difficulty of distinguishing some acquired dermal macular hyperpigmentation disorders. D. LPP Histology shows a flattened, often atrophic epidermis, basal cell degeneration, and a variable band-like or perivascular lymphocytic infiltrate in the upper dermis with melanophages. Its etiology is unknown; UV exposure may play a role in some patients. Key mechanism: Epidermal pigment is located in keratinocytes, whereas dermal pigment persists within melanophages. This distinction helps explain why dermal pigmentation often lasts longer.

1. Classification by distribution and epidermal versus dermal PIH A. Classification by distribution Diffuse: Drug-induced pigmentation, metabolic or endocrine disorders, nutritional deficiencies, sclerodermoid disorders, and occasionally HIV infection. Circumscribed: Post-inflammatory hyperpigmentation (PIH), melasma, erythema dyschromicum perstans (EDP), and lichen planus pigmentosus (LPP). Linear: PIH, drug reactions, pigmentary demarcation lines, and mosaic genetic disorders following Blaschko lines. Reticulated: Prurigo pigmentosa and inherited disorders such as dyskeratosis congenita, Dowling–Degos disease, and other reticulate pigmentary disorders.

todays questions 1.Classification of hyperpigmentation by distribution. Epidermal versus dermal post-inflammatory hyperpigmentation (PIH). 2. Key differences between melasma, erythema dyschromicum perstans (EDP), and lichen planus pigmentosus (LPP). 3. Histopathology and disease mechanisms. 4.Melasma patterns and the limitations of Wood lamp examination. 5. EDP versus LPP. 6. Exogenous ochronosis and tinea versicolor. 7.Heavy-metal pigmentation. 8.Dyskeratosis congenita versus Fanconi anaemia. 9.Inherited dyschromatoses. those question where from chapter 67 Disorders of Hyperpigmentation tomorrow that answers will be posted with other exam traps about this chapter

long time no see I will be posting important question from Bolognia everyday and then add the answers the next day so make sure to add your friend studying for final dermatology exam ( MRCP , Arab board , Iraqi board ,etc)