Aug. 1, 2006  -- Can you imagine what life would be like if you could only come out at night?

If ultraviolet rays -- even from a light bulb -- could be dangerous, perhaps fatal?

Kasey Knauff, 5, of Bellefonte, Pa., faces this reality.

Her strange symptoms began the day she was born: April 10, 2001.

She was rushed to the neonatal intensive care unit and placed under special bilirubin lights to treat what doctors suspected was jaundice. Instead of getting better, Kasey's condition worsened.

A dermatologist was called in to examine her.

Howard Pride of the Geisinger Medical Center in Danville, Pa., removed Kasey's heart monitor patches and was shocked by what he found. The skin underneath the patches was white; the skin around them, red.

The bilirubin lights had caused a full body burn.

The dermatologist now knew that Kasey's skin was sensitive to light. It was another symptom, though, that would lead to a diagnosis -- the color of Kasey's urine was red.

That proved that Kasey was suffering from CEP -- Congenital Erythropoietic Porphyria -- a condition in which the body has trouble producing heme, an essential component of hemoglobin in the blood.

This causes light-activated chemicals called porphyrins to build up, turning bones and urine red, and teeth, a dark brown or purple.

The Knauffs contacted Robert Desnick, a medical geneticist from New York's Mount Sinai School of Medicine, who has been studying porphyrias for 30 years.

After analyzing the DNA of Kasey's parents, his lab found that each parent had passed a different rare mutation for CEP to Kasey. Her older sister Kylie had gotten only one affected gene. That made Kylie a carrier.

Living With CEP

Bili lights aren't Kasey's only enemy.

Any exposure to ultraviolet rays -- the sun, halogen lamps, regular light bulbs -- can burn, blister and scar Kasey's skin. Before leaving the hospital, the Knauffs made sure their house was ultraviolet-proof.

Five years later, the family is still living in the dark. Because the maximum UV light that Kasey can tolerate is 40 watts, she must spend most of her days indoors.

The treatment? Blood transfusions if hemoglobin levels drop too low and a bone marrow transplant if a match is found. While a bone marrow transplant would be a cure, it is risky.

For now, Kasey's hemoglobin levels are fine, and she will not need blood transfusions.

So, until this medical mystery is solved, Kasey's family continues to live one day and one night at a time.