Disorders of Pigmentation

Question 1

What is a “melanocyte” and how does it do its job?

Answer 1

Melanocytes take Tyrosine and converts it to melanin via internal organelles called “Melanosomes.” The job of the melanocyte is to make melanin which causes skin pigmentation when melanosomes are passed off to the keratinocytes.

Question 2

Where are melanocytes found? What tissues are they derived from?

Answer 2

In the basal layer of the epidermis. Derived from Neural crest cells.

Question 3

What disease process is an autoimmune destruction of the melanocytes?.

Answer 3

Vitiligo.

Question 4

What is the clinical manifestation of vitiligo?

Answer 4

Lack of skin pigmentation in focal areas locally, resulting in areas of depigmentation and areas of normal pigmentation where there is no autoimmune attack of melanocytes.

Question 5

How would white people present with vitiligo?

Answer 5

Might not be apparent as in a dark skinned person, so when a pale person tans there will be areas of depigmentation that will be noticable.

Question 6

What is “Albinism” and how does this happen?

Answer 6

This is a congenital defect due to a lack of the enzyme, usually tyrosinase. Without tyrosinase melanocytes cannot turn the tyrosine into melanin in the melanosomes.

Question 7

What are the two clinical presentations of albinism?

Answer 7

Can involve only the eyes (occular form) or the eyes and the skin (called occulocutaneous form).

Question 8

What do people with albinism have an increased risk of?

Answer 8

Skin cancer, particularly basal and squamous cell carcinoma as well as melanoma.

Question 9

What is a “freckle” and what causes it?

Answer 9

It is a small, tan-brown macule that darkens when exposed to sunlight. This is because of an increase of melanosomes in the keratinocytes. NO INCREASE IN MELANOCYTES.

Question 10

What is “Melasma?”

Answer 10

Mask-like hyperpigmentation of the cheeks, associated with preggo and oral contraceptives.

Question 11

What is a “Nevis” aka “Mole?” How can you tell if it is a congenital nevus?

Answer 11

Benign neoplasm of melanocytes. Congenital nevis will be present at birth and will have hair growing out of it.

Question 12

What is a “Junctional Nevis” and who tends to get them?

Answer 12

Children tend to get them (but later in life not congenitally) and this is because there is proliferation of the melanocytes all around the dermal/epidermal junction.

Question 13

What is a “compound nevis?”

Answer 13

Unlike the junctional nevis which is found just at the dermal/epidermal junction, a compound nevis will not only be found at the junction but will also grow all the way through the dermis as well.

Question 14

What is an “intradermal nevis?” Who tends to get them?

Answer 14

Melanocyte proliferation within the dermis, but not at the dermal/epidermal junction. Most common in adults.

Question 15

What should you suspect if there is dysplasia within a mole?

Answer 15

That signifies it is a precursor to melanoma.

Question 16

What is a “Melanoma?”

Answer 16

Despite the -oma suffix this is a MALIGNANT proliferation of the melanocytes (as opposed to the benign nevi). This is the most common cause of death due to skin cancer.

Question 17

What are the risk factors of melanomas?

Answer 17

Whatever increases the risk of UVB exposure, such as increased sunlight, albinism, xeroderma pigmentosum (in which you lack the enzymes necessary to repair the DNA that was damaged due to UVB light).

Question 18

What is “Dysplastic nevus syndrome?”

Answer 18

AD disorder where the patients develop dysplastic nevi, which will lead to eventual melanoma.

Question 19

How does one distinguish a melanoma from a mole?

Answer 19

Look at ABCD. Assymetry, Borders (irregular), Color (not uniform), and Diameter (greater than 6 mm).

Question 20

What are the two growth phases of melanomas?

Answer 20

First is a radial (horizontal) growth along the epidermis and superficial dermis, this is followed by vertical growth where the melanoma grows deep into the dermis.

Question 21

What is the key feature that determines the risk of metastasis of melanomas?

Answer 21

The vertical growth into the skin, the deeper it goes the higher the risk of metastasis. During the radial growth phase there is very little chance of metastasis.

Question 22

What is “Lentigo Maligna Melanoma?”

Answer 22

Basically there is only radial growth of the melanoma in the dermal/epidermal junction. This is one of 4 types of melanomas. Good prognosis.

Question 23

What is “superficial spreading melanoma?” Prognosis? How does this differ from the lentigo maligna melanoma?

Answer 23

Most common sub-type, 1/4 subtypes of melanomas, it has a dominant early radial phase and is associated with good prognosis. LLM would grow where the dermal/epidermal region would be (which goes up and down), the superficial type just goes horizontally across the epidermis doesnt necessarily follow the dermal/epidermal junction.

Question 24

What is the “nodular melanoma?”

Answer 24

The 3rd of 4 types of melanoma, this starts growing into the dermis early and as a result it pushes the epidermis up creating a nodule, hence the name. Since there is vertical growth, nodular melanoma has a poor prognosis.

Question 25

What is “Acral Lentiginous Melanoma?”

Answer 25

Acral means “hands and feet” and this type of melanoma (the last type) will present in the hands and feet.

Question 26

How does acral lentiginous melanoma differ from the demographic of the other 3 types (lentiguous, superficial and nodular)?

Answer 26

There is no sunlight (UVB) exposure as a risk factor and this presents in dark skinned individuals.