nemoci-sympt/DERMATOLOGIE/pigmentace-pokozky/chloasma-melasma/diagnostika

Wood's lamp examination

• 340 to 400nm
• Difference in pigmentation of the affected skin
• Melasmas that are more intensely seen under Wood's light examination respond better to topical treatments

Dermoscopy of melasma

• Characteristic changes
• Possible to see the vascular component
• Present in a large number of patients
• Color intensity of melanin
• Regularity of the pigment network
• Dark brown color and welldefined network
• Located in the stratum corneum
• Shades of light brown and irregularity of the network
• Located in the lower layers of the epidermis
• Blue or bluish-gray color
• Located in the dermis

Dermoscopy (polarized light) of transitional area

Reflectance confocal microscopy (RCM)

• In vivo evaluation of large areas of melasma
• Direct and noninvasive way
• Hypertrophied melanocytes are displayed at high resolution
• Melanin is detected in all layers of the epithelium and dermis, in all cases
• Disfavors the former classification between epidermal or dermal melasma
• Potential technique for assessing treatment response in clinical trials

Colorimetry

• Objectively and reproducibly quantifies and qualifies the reflex of a standardized source of monochromatic lights at a skin site

L*a*b*

• Erythema is best represented by channel a* (redgreen)
• Melanin pigmentation is proportional to the reduction in channel L* (luminance)
• Channel b* represents the variation between yellow and blue
• Measurement of the individual typological angle (ITAO)
• Calculated by the arctangent [(L*-50)/b*]x(180/pí) [4]
• Inversely associated with skin pigmentation [4]

Mexametry

• Single monochromatic source
• Measure surface reflectance intensities
• Does not provide colorimetric values
• Erythema and melanin indices of the surface

MASI index

• Proposed by Kimbrough-Green et al, in 1994
• Clinically quantify the severity of facial melasma
• Most used tool for assessing
• Visual inspection of the face
• Three factors are assessed:
• Affected area (A)
• Hyperpigmentation (D)
• Homogeneity of pigmentation (H) [4]
• Face is divided into four regions:
• Forehead (F)
• Right malar region (MR)
• Left malar region (ML)
• Chin (C) [4]

• Final MASI score is:
• Sum of pigmentation intensity and homogeneity scores
• Multiplied by the area score
• Multiplying factor for each region

• MASI
• Categories: 0 none, 1 mild, 2 moderate, 3 outstanding e 4 maximal.
• Categories: 0 normal skin; 1=< 10%; 2 =10%-29%; 3 =3049%; 4 =50%-69%; 5 =70%-89%; 6 =90%-100%.
• Total score correlates with the highest possible severity of the disease
• Used for documentation of lesions in clinical trials

Histologically

Epidermal

• Hyperpigmentation
• Number of melanocytes is not increased
• Melanocytes are hypertrophied
• Greater number of dendrites and cytoplasmic organelles
• Higher metabolic activity
• Increased amount of melanin in all layers of the epidermis
• Increased number of mature melanosomes [4]

Dermis

• Moderate mononuclear infiltrate
• Presence of mast cells
• Increased vascularity and elastosis
• no differences in dermal pigmentation between the skin with melasma and the adjacent healthy skin [4]

Immunohistochemistry

• protein expression
• Nuclear estrogen receptors were more common in keratinocytes of melasma skin [4]
• Greater immunoreactivity of alpha-MSH
• Increase in the paracrine synthesis of alpha-MSH