What symptom is distinctly associated with Incontinentia Pigmenti?

Incontinentia Pigmenti is a rare genetic disorder primarily affecting the skin, characterized by distinct patterns of skin lesions that evolve over time. The symptom distinctly associated with this condition is linear hypopigmentation. This manifests in a typical four-stage progression, beginning with vesicular lesions that can develop into verrucous lesions, and eventually leading to linear streaks of pigmentation before transitioning into hypopigmented areas.

The prominence of linear hypopigmentation relates directly to the pathophysiology of Incontinentia Pigmenti, where melanocyte development is disrupted due to mutations in the IKBKG gene. This results in irregular pigmentation patterns on the skin.

While the other options may have associations with various other conditions, they are not specifically characteristic of Incontinentia Pigmenti. Hypertrichosis pertains to excessive hair growth, shortened fingers could indicate various skeletal dysplasias, and cleft lip is a congenital deformity not linked to this syndrome. Therefore, linear hypopigmentation stands out as the defining symptom of Incontinentia Pigmenti.