Melanin Absorption and Dermatological Conditions

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Questions and Answers

What describes the commonest type of pigmentary disturbance mentioned?

Complete loss of pigment (correct)

Asymmetrical loss of pigment

Partial loss of pigment with spots

Loss of pigment only on the face

Which of the following is NOT a cause of pigmentary disturbances mentioned?

Nerve involvement in tuberculoid leprosy

Products secreted by certain fungi

Infection from a viral agent (correct)

Scarring in lupus erythematosus

What pattern suggests a neural mechanism in pigmentary changes?

Symmetrical patterns on the arms

Localized pigmentation in spots

Zosteriform pattern (correct)

Splotchy patterns on the back

Mongolian spots are classified as which type of condition?

Developmental condition Signup and view all the answers

Which area is most common for symmetrical loss of pigment?

Hands and forearms Signup and view all the answers

What is the main cause of the acute erysipelas-like eczema described?

Allergy to hair dye containing paraphenylenediamine Signup and view all the answers

Which type of medication is often needed for children with skin conditions, according to the content?

Oral antibiotics Signup and view all the answers

What is the identified allergen for the eczema affecting the face and upper chest?

Miconazole Signup and view all the answers

What does the sharp demarcation of the lesions indicate?

Secondary infection Signup and view all the answers

What type of eczema is characterized by desquamation mainly in the foot and head regions?

Subacute eczema Signup and view all the answers

Which statement is true regarding the use of systemic steroids?

They should be used in moderation. Signup and view all the answers

What is the common allergen associated with eczema on the patient's neck?

Nickel in cheap jewelry Signup and view all the answers

What type of allergic reaction is primarily highlighted in this content?

Contact dermatitis Signup and view all the answers

How does melanin behave differently in black skin compared to white skin?

Melanin is not reabsorbed and reaches the stratum corneum in black skin. Signup and view all the answers

What can be inferred about the visibility of certain dermatological conditions in black skin?

Conditions like erythema are more pronounced in black skin. Signup and view all the answers

What is a notable disadvantage regarding heat exposure for black individuals?

They are more liable to heatstroke than white individuals. Signup and view all the answers

In the context of diagnosing skin conditions, what can be said about lichen planus in black skin?

Wickham's striae are less visible in black skin. Signup and view all the answers

What color represents erythema in black skin, according to the information provided?

Dark violet Signup and view all the answers

What phenomenon can occur when cotton wool soaked in ether is rubbed on black skin?

It becomes dark in color. Signup and view all the answers

How does black skin react to UV rays compared to white skin?

It is less likely to develop solar keratoses. Signup and view all the answers

Which of the following dermatological terms cannot be interpreted literally in black skin?

All of the above conditions. Signup and view all the answers

What is a significant characteristic of discoid lupus erythematosus that can complicate diagnosis?

Oedema of the lesions Signup and view all the answers

Which group is more commonly affected by discoid lupus erythematosus?

Women Signup and view all the answers

What type of permanent skin change is associated with discoid lupus erythematosus?

Permanent scarring Signup and view all the answers

In systemic lupus erythematosus, what type of lesions are typically observed on the scalp?

Large plaques of alopecia Signup and view all the answers

Which symptom is commonly seen in the early stages of systemic lupus erythematosus?

Central point of ulceration Signup and view all the answers

What is the primary histological feature associated with parakeratosis in psoriasis?

Thickening of the epidermis Signup and view all the answers

Which of the following symptoms is NOT typically associated with psoriasis?

Severe sensory changes Signup and view all the answers

What role does ultraviolet light play in the treatment of psoriasis?

It is used to de-scale lesions Signup and view all the answers

Which treatment is considered very effective for psoriasis but has ocular toxicity issues?

Dithranol therapy Signup and view all the answers

How has the prevalence of psoriasis changed in Africa over the years?

It has recently increased in urban areas Signup and view all the answers

Which of the following best describes the common complications associated with psoriasis?

Arthropathy Signup and view all the answers

What indicates that psoriasis may have a civilizational factor in its development in Africa?

It has emerged more in urban settings Signup and view all the answers

Which condition is mentioned as having similar lesions to those of psoriasis?

Onchocerciasis Signup and view all the answers

Study Notes

Melanin Absorption and Skin Color

Melanin is absorbed differently in people with different skin tones.
In people with lighter skin, melanin does not penetrate past the first few layers of the epidermis, while in people with darker skin, melanin reaches the stratum corneum.
This difference in absorption is easily demonstrated by rubbing a cotton wool swab soaked in ether on the skin of a person with darker skin. The swab will turn dark, even if the person is very clean.

Dermatological Conditions and Skin Tone

In people with darker skin, typical dermatological terms such as erythema and pityriasis rosea may present differently due to the presence of melanin.
Erythema, which is typically red, appears as a dark violet or black in people with darker skin.
The 'homme rouge' of Hallopeau, characterized by a reddish hue, presents as a slate-grey color in people with darker skin tones.
It can be challenging to diagnose conditions like measles and syphilis in people with darker skin because of the melanin's influence on the appearance of skin lesions.

Melanin and Sun Protection

Melanin provides protection against ultraviolet (UV) rays, which explains why people with darker skin are less susceptible to solar keratoses and basal-cell carcinomas.
Despite the protective effect of melanin against UV rays, it does not offer protection against infrared rays.
People with darker skin are more prone to heatstroke than people with lighter skin, even with a better-developed superficial cutaneous vasculature.

Dermatoses and Skin Tone

In many dermatoses, the primary lesions are larger and more pronounced in individuals with darker skin tones.
This difference is seen in lichen planus, where Wickham's striae (fine white network on the surface of papules) are readily visible to the naked eye in individuals with darker skin, but may not be as easily visible in Caucasians.
Similarly, pityriasis rosea presents differently in individuals with darker skin, exhibiting a phase where the skin is not red.

Pigmentary Disturbances

Pigmentary disturbances can arise from various mechanisms, including:
- Nerve involvement (e.g., tuberculoid leprosy)
- Products secreted by certain fungi and spirochaetes (e.g., syphilis)
- Cancers
- Scarring (e.g., lupus erythematosus)
- Cosmetics
- Developmental conditions (e.g., Mongolian spots)

Vitiligo

Vitiligo is a condition characterized by the loss of pigment, usually complete.
The most common type of vitiligo is symmetrical and affects the hands and forearms.
Other patterns of vitiligo, such as the zosteriform pattern, suggest a neural mechanism.

Psoriasis

Psoriasis is a chronic skin condition characterized by thickened epidermis and hyperpigmentation.
The clinical diagnosis of psoriasis is confirmed by gently scratching the lesion, revealing the three classical stages: waxy surface, loose flaky scales, and erythema with fine bleeding points.
Psoriasis was rare in Africa and the tropics, but has become more common in recent years, suggesting it may be a disease of civilization.
Psoriasis is generally a harmless disease, but can be complicated by arthropathy.

Treatment of Psoriasis

Treatment for psoriasis is largely based on ultraviolet light exposure.
In Africa, where sun exposure is high, ultraviolet lamps are unnecessary.
Psoralens are dangerous and should be avoided.
Descaling the lesions with 5% salicylic acid ointment allows the rays to penetrate effectively.
Dithranol therapy is highly effective and inexpensive, but its ocular toxicity makes it unsuitable for most outpatients.

Lupus Erythematosus

Lupus erythematosus is a chronic autoimmune disease that can affect the skin, joints, and other organs.
Discoid lupus erythematosus is characterized by red, scaly plaques on the skin, often with scarring and depigmentation.
The typical presentation of discoid lupus erythematosus on the scalp is characterized by large plaques of alopecia, with an active erythematous periphery and spreading central depigmentation.
Systemic lupus erythematosus, a more serious form, affects multiple organs and can lead to significant health problems.

Eczema

Eczema is a common skin condition that causes inflammation, redness, and itchiness.
Eczema can be triggered by various factors, including allergies, irritants, and genetics.
Treatment for eczema involves identifying and avoiding triggers, and using topical medications such as corticosteroids and moisturizers.
In severe cases, systemic medications may be necessary.

Other

It is important to note that information presented may not be current and medical advice should always be sought from a qualified healthcare professional.

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Description

This quiz explores the differences in melanin absorption and its impact on dermatological conditions across various skin tones. Understanding how certain skin disorders present differently based on skin color is crucial for accurate diagnosis and treatment. Test your knowledge on these important dermatological concepts.