[How are the Blaschko lines arranged on the scalp?]

Area of Science:

• Dermatology and Genetics
• Developmental Biology

Background:

• Blaschko's lines describe linear patterns of nevoid skin lesions.
• These lines map epidermal development and X-chromosome inactivation.
• Previous atlases lacked scalp coverage due to limited case reports.

Observation:

• A case of oral-facial-digital syndrome presented with linear alopecia on the scalp.
• The alopecia exhibited spiral streaks, resembling normal vertex patterns but with altered hair growth direction.
• This observation addresses a gap in the Blaschko's lines atlas.

Findings:

• The linear alopecia pattern in this patient is hypothesized to represent Blaschko's lines.
• The pattern likely reflects functional X-chromosome mosaicism, common in X-linked dominant traits like oral-facial-digital syndrome.

Implications:

• This finding expands the known distribution of Blaschko's lines to include the scalp.
• It provides a potential in vivo marker for X-chromosome inactivation patterns in scalp development.
• Further research can explore the utility of these lines in understanding scalp dermatoses and genetic mosaicism.