Tuberous Sclerosis Complex

A 3-year-old boy is referred for evaluation of new-onset seizures and developmental delay. Skin examination under Wood lamp illumination reveals multiple hypopigmented macules with a characteristic lance-ovate or ash-leaf shape distributed over the trunk, buttocks, and lower limbs. Facial examination shows early angiofibromas, and imaging confirms cortical tubers and subependymal nodules consistent with tuberous sclerosis complex. The structure marked **A** in the diagram represents the earliest and most common cutaneous manifestation of this condition. Which of the following best describes the clinical significance of this finding?