In Reply:-We would like to thank Drs. Mamet and Schoenfeld for their instructive comments and corrections. We completely agree that porphyria had not been definitively diagnosed and that the pattern of porphyrin and porphyrin precursor elevation is consistent with any neurogenic porphyria. However, it should be noted that the patient's liver function tests had returned to the normal range (except for a minimally elevated alanine transaminase level) on the day before the urine porphyrin collection. Furthermore, we noted that propofol (which could have interfered with the colorimetric assay) was at near-undetectable levels at the time of urine collection, thus making both liver dysfunction or drug effect unlikely as the cause of the abnormal laboratory results. Regrettably, testing for lead poisoning was not performed at that time; however, clinically, there was no feature to suggest this as a possibility.
The patient was referred to our center for his ablation and has not followed up with us. We strongly recommended that a fecal porphyrin profile as well as a coproporphyrinogen oxidase level analysis be performed by this primary physician.
Despite the above discussion, in our opinion, the clinical syndrome and abnormal tests as outlined in our report make latent neurogenic porphyria manifested by propofol an important and likely possibility. We believe that this observation should be considered when administering large amounts of propofol to porphyric patients until larger studies have demonstrated otherwise.
Samuel J. Asirvatham, M.D.
Department of Electrophysiology; St. Mary's Hospital; Rochester, Minnesota 55902;Asirvatham.samuel@mayo.edu
(Accepted for publication March 23, 1999.)
