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Questions and Answers
Which of the following factors does NOT influence normal pigmentation of the skin?
Melanocytes are present in higher abundance in tan macules compared to adjacent normal skin.
False
What is the primary action of tyrosinase?
To synthesize melanin from tyrosine.
Melanosis occurs due to the increase in the number and distribution of __________ in the epidermal melanin unit.
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Match the following pigmentation disorders with their characteristics:
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Which of the following is a common treatment for melasma?
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Tan macules generally increase in frequency during winter months.
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What are melanosomes, and what is their function?
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What does 'ochronosis' refer to in relation to skin pigmentation?
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Exogenous ochronosis is commonly reported in lighter racial/ethnic groups.
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What are the common clinical features of exogenous ochronosis?
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Exogenous ochronosis is mostly associated with medications like 4% __________.
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Match the following skin conditions with their characteristics:
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What method remains the gold standard for diagnosing exogenous ochronosis?
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Treatment for exogenous ochronosis has a universally effective solution.
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What triggers post-inflammatory hyperpigmentation (PIH)?
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Solar lentigines are commonly found on the __________ and hands.
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What is typically a significant exacerbating factor for exogenous ochronosis?
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Study Notes
Normal Skin Pigmentation
- Skin pigmentation is influenced by melanin amount and depth, vascularity, carotene, and horny layer thickness.
- Skin browning depends on melanosomes transferring from melanocytes to keratinocytes.
- Melanosomes are cytoplasmic particles synthesized in melanocytes and distributed among basal epidermal cells.
- Each epidermal melanocyte secretes melanosomes into surrounding keratinocytes forming the epidermal melanin unit.
- Melanosomes are sites of melanin synthesis by tyrosinase action on tyrosine.
- Skin color variations between individuals and races are due to melanosome melanization degree, number, and distribution.
Ephelides (Freckles)
- Tan macules less than 5 mm in diameter on sun-exposed areas like the nose, cheeks, hands, and upper trunk.
- Early indicators of solar damage.
- Increased melanin production without melanocyte proliferation.
- Melanocytes are less abundant than in adjacent normal skin but are larger and contain more mature melanosomes.
- Increase in summer and decrease during winter.
- Best treated with peeling agents and depigmenting creams.
- Sun exposure should be limited or avoided, and sunscreens should be applied.
Melasma (Chloasma Faciei)
- Brown macules on the malar prominences and forehead.
- Exact cause unknown, but sun exposure, contraceptive pill intake, and genetic predisposition are important factors.
- Occurs during pregnancy and clears within a few months after delivery.
- Also seen in menopause, ovarian disorders, and in people taking Dilantin and Tetracycline.
- May be treated with bleaching, depigmenting creams, lasers, procedures like chemobrasasion, iontophoresis, and sunscreen use.
Ochronosis
- Derived from the Greek word ""ochre"" meaning yellow discoloration.
- Two forms: endogenous and exogenous.
Exogenous Ochronosis
- Majority of cases reported in darker racial/ethnic groups in Africa, India, Thailand, China, and Singapore.
- Worldwide incidence is unknown, but assumed to be low.
Clinical Features of Exogenous Ochronosis
- Asymptomatic blue-black and gray-black hyperpigmented macules.
- Found on the face (malar, temples, lower cheeks), posterolateral neck, back, and extensor skin of extremities.
- Later stages include progressive hyperpigmented colloid milium (caviar-like lesions), papulo-nodular lesions, and areas of scarring.
- No systemic involvement noted.
Etiology and Pathogenesis of Exogenous Ochronosis
- Results from using certain medications that form a homogentisic acid polymer-like substance during their metabolism.
- Most frequently reported in association with topical 4% hydroquinone, phenol, resorcinol, and oral quinine, an antimalarial.
- Exacerbating factors include unprotected ultraviolet light exposure, prolonged application of the offending medication on large surface areas, and use of topical resorcinol, phenol, and mercury.
Diagnosis of Exogenous Ochronosis
- Early stages may appear similar to melasma, but dermatoscopy may help differentiate them.
- Dark-brown globules and globular-like structures are seen on a diffuse brown background.
- Skin biopsy remains the gold standard for diagnosis.
- Histopathologically, there is a collection of yellowish-brown (ochronotic) banana-shaped globules in the papillary dermis.
- Homogenous edematous dermal collagen also may be seen.
- Early stages may be clinically indistinguishable from melasma, especially in Asians.
- Without cessation of the offending agent, exogenous ochronosis is progressive.
Management of Exogenous Ochronosis
- Treatment is rarely helpful.
- Stopping the offending drug is essential to prevent progression.
- Broad-spectrum sunscreen and sun avoidance are important.
- Topical retinoids, α-hydroxy acids, corticosteroids, and physical therapies such as chemical peels and quality switched lasers have been reported in treatment, but no universally efficacious treatment has been documented.
Post-Inflammatory Hyperpigmentation (PIH)
- Brownish discoloration from the accumulation of iron and melanin pigments in the dermis.
- Occurs after friction, trauma, inflammatory dermatoses/eczema such as acne, atopic eczema, or lichen planus.
- Some medications may darken PIH, including antimalarial drugs, tetracyclines, and anticancer drugs (bleomycin, 5-FU, doxorubicin).
- Usually resolves after treatment of the underlying causes, though slow spontaneous improvement can be expected.
Solar Lentigines (Age Spots/Actinic Lentigines)
- Benign brownish pigmented macules in adults, especially individuals with fair skin who easily burn and tan poorly.
- Arise in middle age and result from sun damage.
- Most often found on the face and hands, and are larger and more defined than freckles.
- Tend to persist for longer periods and do not disappear during winter.
Treatment of Solar Lentigines
- Educate the patient to limit sun exposure.
- Sunscreen usage should have a high SPF factor (SPF 50), good broad-spectrum coverage against UV radiation (UVA), and should be applied liberally and frequently.
- Topical treatments include:
- Hydroquinone
- Azelaic acid
- Tretinoin
- Glycolic acid (α-hydroxy acids)
- Kojic acid
- Arbutin
- Licorice
- Niacinamide
- Further treatment options include:
- Chemical peels
- Laser treatment (multiple sessions)
- IPL (Intense Pulsed Light)
- Cryotherapy
Pityriasis Alba
- Also known as Pityriasis Simplex and Erythema Streptogenes.
- Hypopigmented round, scaly patches on the face, upper arms, neck, or shoulders.
- Asymptomatic.
- Occur chiefly in children and teenagers.
- Unknown etiology, but thought to be due to excessive dry skin following exposure to strong sunlight.
- Prognosis is good with spontaneous healing within several weeks.
Vitiligo
- Acquired depigmented white patches (lack melanocytes).
- Commonly affects the face, upper part of the chest, dorsal aspects of the hands, knees, axillae, groin, eyes, nose, mouth, ears, nipples, umbilicus, penis, and clitoris.
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Description
This quiz explores the mechanisms behind normal skin pigmentation and the formation of freckles. It covers the roles of melanin, melanocytes, and melanosomes in skin color variations and responses to sun exposure. Perfect for anyone studying dermatology or skin biology.
