Pediatrics International (2005) 47, 550–553 Original Article Characteristics of hyperthermia and its complications in patients with Prader Willi syndrome ERDAL INCE, 1 ERGIN ÇIFTÇI, 1 MUSTAFA TEKIN, 2 TANIL KENDIRLI, 3 ERCAN TUTAR, 4 NAZAN DALGIÇ, 1 SELIM ÖNCEL 1 AND ÜLKER DOGRU 1 Divisions of 1 Pediatric Infectious Disease, 2 Genetics, and 3 Intensive Care Unit, and 4 Cardiology, Department of Pediatrics, Ankara University School of Medicine, Dikimevi, Ankara, Turkey Abstract Background: Thermoregulation problems, resulting in hypo- or hyperthermia, have been infrequently reported in children with Prader Willi syndrome (PWS), yet their clinical details remained unknown. Methods: The clinical characteristics of three infants with PWS are reported. Results: Etiologies of high fever could not be identified in three children with PWS. One of these children was also admitted to the intensive care unit with extremely high body temperature in a life-threatening condition, similar to septic shock, without a plausible explanation. Conclusion: Hyperthermia may be a part of the clinical spectrum in young infants with PWS and should be carefully monitored, since it may cause life-threatening complications. Key words fever, hyperthermia, Prader-Willi syndrome, septic shock. Prader Willi syndrome (PWS) is a well-known genetic disorder, which affects one in 10.000–15.000 live births. Its typical clinical features include central hypotonia, feeding difficulties during infancy, developmental delay, obesity usually starting after 1 year of age, hypogonadism, and distinctive physical appearance. The definitive diagnosis of PWS can be made with molecular and/or molecular cytogenetic investigations. 1–3 Although it has long been believed that most of the typical findings of PWS can be explained with hypothalamic dys- function, a structural defect in hypothalamus has not been demonstrated. Thermoregulation problems in patients with PWS have been mentioned in only few publications, for which a hypothalamic dysfunction has also been speculated. 4–9 However, detailed characteristics of thermoregulation problems and their clinical presentations have remained unknown. In this report, we present three infants with PWS, who were evaluated for fever of unknown origin starting in the early months of their lives. Our findings indicate that hyper- thermia may be an internal feature of PWS and may result in life-threatening complications. Patient 1 This boy was the third child of a 35-year-old mother and a 36-year-old father. He was born at term by normal vaginal delivery following an uncomplicated pregnancy. The mother noticed decreased fetal movements compared with her previous pregnancies. His birth weight and length were 3210 g (25th–50th centile) and 50 cm (25th–50th centile), respec- tively. He was admitted to the neonatal intensive care unit and observed for 2 days after delivery because the amniotic fluid was meconium-stained and onset of spontaneous respi- rations was delayed. Muscle hypotonia was noted during his hospital stay, which was the only pathological finding at discharge. He had decreased sweating and dermographism, which was also noted by the parents. He was readmitted to a regional hospital because of fever, presumed to be due to pneumonia, when he was 15 days old. His clinical findings quickly improved with intravenous antibiotics, although fever remained continuously high. He was admitted to the Department of Pediatrics, Ankara University School of Medicine, at 1 month of age, because of persistent high fever. His weight, length, and head circumference were 4300 g (50th–75th centile), 56 cm (75th centile), and 38.2 cm (75th centile), respectively. His rectal temperature was 38.8°C, heart rate was 146 b.p.m, respiratory rate was 42 breaths/min, and blood pressure was 68/42 mmHg upon admission. Marked hypotonia was noted with weak deep tendon reflexes and swallowing difficulties. A summary of the phenotypic Correspondence: Erdal Ince, Hosdere caddesi 23/21 06550, Yukar- iayranci, Ankara, Turkey. Email: ince@dialup.ankara.edu.tr Received 30 October 2004; revised 25 January 2005; accepted 23 February 2005.