US officials detained a cancer patient for four hours before allowing him entry into the country because one of the drugs he took had wiped out his fingerprints.
His oncologist is now advising all cancer patients, prescribed capecitabine, a common cancer drug, to carry a doctor's letter with them if they want to travel to the US.
The oncologist informed that several other cancer patients have reported loss of fingerprints on their blog sites, and some have also commented on similar problems entering the US.
Eng-Huat Tan, a senior consultant at the National Cancer Centre, Singapore, described how his patient, a 62-year-old man, had head and neck cancer that had spread but had responded well to chemotherapy.
To help prevent a recurrence of the cancer, the patient was prescribed capecitabine, a common drug used in treating head and neck, breast, stomach and colorectal cancers.
One of its side-effects can be hand-foot syndrome - a chronic inflammation of the palms or soles of the feet and the skin can peel, bleed and develop ulcers or blisters.
"This can cause eradication of finger prints with time," said Tan.
The patient, identified as only S, developed a mild case of hand-foot syndrome, and because it was not affecting his daily life he was kept on a low dose of the drug.
"In December 2008, after more than three years of capecitabine, he went to the United States to visit his relatives," wrote Tan.
"He was detained at the airport customs for four hours because the immigration officers could not detect his fingerprints. He was allowed to enter after the custom officers were satisfied that he was not a security threat."
"He was advised to travel with a letter from his oncologist stating his condition and the treatment he was receiving to account for his lack of fingerprints to facilitate his entry in future."
S was not aware that he had lost his fingerprints before he travelled, said a press release issued by Tan.
Foreign visitors have been asked to provide fingerprints at US airports for several years now, and the images are matched with millions of visa holders to detect whether the new visa applicant has a visa under a different name.
"These fingerprints are also matched to a list of suspected criminals," wrote Tan.
The incident is highlighted in a letter to Annals of Oncology, published online on Wednesday.