Make an appointment:
(i.e. Dermatologists)

My 5 year old has suddenly developed long dark hair on his arms and legs. His dad and I, we are both caucasian. Why did that happen?

The hair on his head is not quite blonde but certainly very fair and also quite fine. I have medium brown hair, barely any hair on my arms, and minimal hair on my legs. His dad, although dark haired, is not very hairy (none on chest/back, average arms/legs). We are both caucasian. His 11 year old sister has only just started to develop hairs which are fair and fine. His 8 year old brother has nothing.
This is an interesting question and I recommend that you discuss it with your doctor or your son's pediatrician. While it is possible that this is just a different manifestation of his genetic makeup, it is also possible that there could be something more at play. There are many rare and unusual conditions that could potentially lead to this sort of finding, but it is hard to know if this is something serious or something normal without more information. An examination of what you are describing would help, but it may be that some testing would be valuable as well. If he is growing well, and meeting all of his other targets as far as development goes, it is possible that this is just something normal that is having an unusual presentation. Speaking with your doctor or your son's pediatrician is the best place to start, so please speak with your doctor.
This answer is for general informational purposes only and is not a substitute for professional medical advice.
If you think you may have a medical emergency, call your doctor or (in the United States) 911 immediately. Always seek the advice of your doctor before starting or changing treatment. Medical professionals who provide responses to health-related questions are intended third party beneficiaries with certain rights under Zocdoc’s Terms of Service.

Other Pediatricians