Complex sentence: At age 8 Cassandra developed a rather innocuous strain of Acne vulgaris which later transformed into an aggressive strain of acne conglobata by the time she was fourteen that engulfed her entire face and most of her body.
Split into simpler sentences: At age 8 Cassandra developed a rather innocuous strain of Acne vulgaris which later transformed into an aggressive strain of acne conglobata. By the time she was fourteen her severe skin condition had engulfed her entire face and most of her body.