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These conditions are marked by an intrinsic problem with melanocytes, the pigment producing cells.
Vitiligo
This is an acquired autoimmune condition which leads to the destruction of melanocytes causing depigmentation of the skin (leukoderma).
– In people with darker skin, it can be very apparent and psychologically scarring
– It is more common in India and the onset is usually in youths before the age of 30.
Associations:
Type 1 diabetes, Addison’s disease, thyroid disease
– Connective tissue disorders –> SLE, rheumatoid arthritis
Appearance:
Well-defined patches of depigmentation (on face, neck fingers and toes)
– Koebner phenomenon occurs –> development of lesions on sites of injury
– Can affect the hair, eyelashes and body hair too
Management
– Sunblock affected areas due to risk of skin cancer
– Medical therapy for new lesions –> Topical corticosteroids + Phototherapy
Malignant melanoma
This is a malignant neoplasm of melanocytes, which occurs in 2 phases:
i) Radial growth along epidermis and superficial dermis
ii) Vertical growth into deep dermis
– Most frequent mutation is in BRAF which leads to uncontrolled cell division
Appearance – Starts as an unusual freckle/mole but then becomes abnormal with ABCD:
– Asymmetry
– Borders irregular
– Colour not uniform
– Diameter >6mm
– Suspect melanoma if:
– Change in size, shape, colour, or sensation
– Diameter >6mm or if the lesion is oozing or bleeding
Types – There are 4 main types of melanoma
a) Superficial spreading – Most common (70%) seen in limbs and torso of young people
b) Nodular – 2nd most common and most aggressive which looks more like a nodule which can bleed
c) Lentigo maligna – A type of melanoma in-situ which progresses slowly but can become invasive
d) Acral lentiginous – Rare form with pigmentation under nails/palms/soles of black and Asian people
Diagnosis – Skin biopsy and histology
Treatment – Excision biopsy + sentinel lymph node mapping
Prognosis
– The Breslow Thickness (invasion depth of tumour) is single most important factor.
– If <1mm, almost all patients survive 5-years
– If >4mm, 50% less than half survive 5 years
– Tumour usually metastasises to the lung, other parts of skin, bone and brain
Melasma
This is a mask like hyperpigmentation of the cheeks, upper lip and forehead
– Thought to be due to melanocyte dysfunction leading to more melanin production
– It is associated with pregnancy and oral contraceptives
Management – Hydroquinone (topical depigmenting agent)
Albinism
An autosomal recessive condition leading to a congenital lack of pigmentation
– There is an enzyme defect (tyrosinase) which impairs melanin production
– It can involve the eyes (ocular) and skin
– Gives increased risk of skin cancers, so patients must be very wary of UV rays
