Masruha et al. reply

Abstract

SIR–We read with great interest and appreciation the comments made by Duman and Durmaz regarding our article. In their letter, they suggested that our patients’ symptoms may have been caused by a secondary effect of hypermelatoninemia, as they have previously described in a published case report. In their study, a female patient exhibited symptoms of spontaneous periodic hypothermia and hyperhidrosis. She displayed extremely high levels of melatonin in her serum and 6-hydroxymelatonin sulphate in urine samples obtained during her attacks. However, subsequent 24-hour urine studies revealed the presence of 5-hydroxyindoleacetic acid (5-HIAA) at 1.9 mg (normal), vanillylmandelic acid at 1.2 mg (normal), and homovanillic acid (HVA) at 2.2 mg (normal). These data are not in agreement with our findings, as both of our patient cases consistently demonstrated decreased levels of 5-HIAA and HVA in the cerebrospinal fluid. However, this inconsistency may be explained by a difference in the sensitivity of measurements obtained from urinary samples compared with measurements obtained from cerebrospinal fluid samples. We agree that increased levels of melatonin in blood and 6hydroxymelatonin sulphate in urine could be responsible for this disorder, and that hypermelatoninemia may explain our findings of low cerebrospinal fluid levels of 5-HIAA and HVA. We think that future studies examining melatonin levels as well as the determination of cerebrospinal fluid metabolites in the serum of patients who exhibit spontaneous hypothermia and hyperhidrosis will be very important, because only the reproduction of these findings will enable the determination of hypermelatoninemia as a cause of the disorder.