A) He has autoimmune destruction of melanocytes, and his condition does not carry an increased risk of skin cancer

This patient likely has vitiligo, characterized by irregular areas of compete depigmentation of the skin. These areas are particularly noticeable in patients with darker skin, especially around body orifices like the mouth, nostrils, eyes, genitalia, and umbilicus. It is caused by autoimmune destruction of melanocytes and does not carry an increased risk for cancer. In fact, some studies have actually shown that patients with vitiligo have a decreased susceptibility to melanoma.

Answer B is incorrect because the number of melanocytes in human skin of all types is essentially constant though the number, size, and manner in which melanosomes are distributed within keratinocytes vary.

Answer C describes albinism, where patients are born with a normal number of melanocytes, but they have decreased melanin production due to decreased tyrosinase activity or defective tyrosine transport. This condition does have an increased risk of skin cancer.

Answer D describes tinea versicolor, caused by a yeast-like fungus of the Malassezia species. Degradation of lipids produces acids that damage melanocytes, and leads to formation of hypopigmented, hyperpigmented, and/or pink patches. This condition can be treated with selenium sulfide, or topical and/or oral anti fungal agents.

Answer E is incorrect as the description of the skin is not consistent with melanoma.

Key Learning Point

Vitiligo is characterized by irregular areas of complete depigmentation of the skin, is caused by autoimmune destruction of melanocytes, and does not carry an increased risk for skin cancer.