Podcast
Questions and Answers
What is the genetic basis for generalised hypopigmentation in albinism?
What is the genetic basis for generalised hypopigmentation in albinism?
- Genetic defect in the enzyme tyrosinase (correct)
- Deficiency of melanin receptors
- Complete absence of melanocytes
- Increase in melanocyte activity
What are common features of oculocutaneous albinism?
What are common features of oculocutaneous albinism?
- Dark hair and increased melanin in skin
- Pigmented skin and normal vision
- Blond hair, poor vision, and severe photophobia (correct)
- Localized pigmentation and increased sunlight tolerance
Which condition is characterized by localized loss of pigmentation in the skin?
Which condition is characterized by localized loss of pigmentation in the skin?
- Generalized hyperpigmentation
- Leucoderma (correct)
- Albinism
- Photodermatitis
What is a common risk associated with chronic sun exposure in individuals with albinism?
What is a common risk associated with chronic sun exposure in individuals with albinism?
What distinguishes vitiligo from leucoderma?
What distinguishes vitiligo from leucoderma?
What is the role of tyrosinase in melanocyte cells?
What is the role of tyrosinase in melanocyte cells?
Which of the following conditions is associated with generalised hyperpigmentation?
Which of the following conditions is associated with generalised hyperpigmentation?
What is the DOPA reaction used to identify?
What is the DOPA reaction used to identify?
Café-au-lait spots are commonly seen in which condition?
Café-au-lait spots are commonly seen in which condition?
Which entity is indicative of focal hyperpigmentation around the mouth?
Which entity is indicative of focal hyperpigmentation around the mouth?
Rain-drop pigmentation is associated with which type of poisoning?
Rain-drop pigmentation is associated with which type of poisoning?
What typically characterizes lentigo?
What typically characterizes lentigo?
Melanin is NOT normally found in which of the following locations?
Melanin is NOT normally found in which of the following locations?
Flashcards
Dermatopathic Lymphadenitis
Dermatopathic Lymphadenitis
A condition where melanin pigment accumulates in macrophages within lymph nodes draining skin lesions.
Albinism
Albinism
A complete lack of melanin production due to a genetic defect in the tyrosinase enzyme.
Oculocutaneous Albinism
Oculocutaneous Albinism
A type of albinism affecting both skin and eyes, characterized by blond hair, poor vision, and sensitivity to sunlight.
Leucoderma
Leucoderma
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Vitiligo
Vitiligo
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Endogenous pigments
Endogenous pigments
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Melanin
Melanin
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Melanocytes
Melanocytes
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Melanophores
Melanophores
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Tyrosinase
Tyrosinase
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Dark pigment in cells after DOPA incubation
Dark pigment in cells after DOPA incubation
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Generalised hyperpigmentation
Generalised hyperpigmentation
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Focal hyperpigmentation
Focal hyperpigmentation
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Study Notes
Endogenous Pigments
- Endogenous pigments are normal cellular components or accumulated substances (melanin, alkaptonuria products, haemoprotein-derived pigments, lipofuscin)
- Melanin is a brown-black pigment found in hair, skin, mucosa (in places), choroid, meninges, and adrenal medulla.
- Synthesised in melanocytes and dendritic cells (basal epidermis).
- Stored in cytoplasmic granules of melanophores (underlying dermis).
- Melanocytes contain tyrosinase, for melanin synthesis from tyrosine.
- Tyrosinase inactivity may result in no visible melanin.
- DOPA reaction (incubating tissue in DOPA) detects tyrosinase presence (dark pigment) - distinguishes amelanotic melanoma.
Melanism Disorders
-
Generalised Hyperpigmentation:
- Addison's disease: Skin (light-exposed areas) and buccal mucosa hyperpigmentation.
- Chloasma (pregnancy): Face, nipples, genitalia hyperpigmentation (due to oestrogen). Similar appearance in oral contraceptive users.
- Chronic arsenical poisoning: "Rain-drop" skin pigmentation.
-
Focal Hyperpigmentation:
- Café-au-lait spots: Pigmented patches in neurofibromatosis and Albright's syndrome.
- Peutz-Jeghers syndrome: Peri-oral pigmentation.
- Melanosis coli: Pigmented colon mucosa.
- Melanotic tumours: Benign (pigmented naevi), malignant (melanoma); increased melanogenesis.
- Lentigo: Pre-malignant condition; hyperpigmentation on hands, face, neck, arms.
- Dermatopathic lymphadenitis: Melanin deposition in lymph node macrophages.
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Generalised Hypopigmentation:
- Albinism: Tyrosinase deficiency; no pigment in skin, blond hair, poor vision, severe photophobia, high sunlight sensitivity; pre-cancerous lesions and skin cancers possible with chronic sun exposure.
-
Localised Hypopigmentation:
- Leucoderma: Autoimmune loss of skin pigmentation.
- Vitiligo: Common local skin hypopigmentation (possible familial tendency).
- Acquired focal hypopigmentation: Due to various causes.
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