Albinism

[Miracoli]

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Cause of albinism:
a. Lack of tyrosinase activity in melanocytes
b. Failure of neural crest cell migration during development
c. a&b

 

[metukah]

I think it can be either A or B. I have seen this in an NBME question. FA writes both of these options.
With albinism, the # of melanocytes is supposed to be normal (ddx: vetiligo), however, if the neural crest cells fail to migrate, wouldn't this be a decreased number of melanocytes?

 

[Miracoli]

I think it can be either A or B. I have seen this in an NBME question. FA writes both of these options.
With albinism, the # of melanocytes is supposed to be normal (ddx: vetiligo), however, if the neural crest cells fail to migrate, wouldn't this be a decreased number of melanocytes?

Yeah, exactly there is a question in NBME4 that is asking about albinism and both choices are there.

 

[dyspareunia]

A. Pretty sure the epidermal stem cells (surface ectoderm) can differentiate into melanocytes as well.

 

[thehundredthone]

Failure of neural crest cells to migrate can cause a decrease in the number of melanocytes and I think consitutes the ABCD/Waardenburg type IV syndrome which has features of albinism. However, strictly speaking, like you said, albinism is the decrease in tyrosinase activity of melanocytes. Neurectodermal derivative melanocytes contribute to ocular melanin.

Did the question just ask the cause of albinism or was there anything else? I would lean towards a) unless there were other features of neural crest cell migration defects.

 

[Miracoli]

It was a typical oculocutaneous albinism case. A is for sure but how about B is the question. Check your FA.