Rom J Morphol Embryol 2012, 53(3):527–532 ISSN (print) 1220–0522 ISSN (on-line) 2066–8279 ORIGINAL P APER The heterogeneity of craniofacial morphology in Prader–Willi patients D. BELENGEANU 1) , C RI STI NA BRATU 2) , MONI CA S TOI AN 3) , A. MOTOC 4) , E LI ORMEROD 5) , ANGELA C ODRUŢA P ODARI U 6) , S I MONA FARCAŞ 3) , NI COLETA ANDREESCU 3) 1) College of Dental Technique 2) Department of Pediatric Dentistry and Orthodontics, Faculty of Dentistry 3) Department of Microscopic Morphology, Genetics 4) Department of Anatomy and Embryology “Victor Babeş” University of Medicine and Pharmacy, Timisoara, Romania 5) Department of Medical Genetics, Oslo University Hospital, Oslo, Norway 6) Department of Medical Dental Prevention and Oral Health, “Victor Babeş” University of Medicine and Pharmacy, Timisoara, Romania Abstract Prader–Willi syndrome is a complex genetic disorder with narrow spectrum of facial phenotypic signs, which make the clinical diagnosis difficult in some cases. There are several reports describing the craniofacial appearance of Prader–Willi patients, but there are only a few cephalometric studies for these patients. In this study were included 18 patients with Prader–Willi syndrome and a control group of 18 subjects of both sexes selected based on specific criteria. The cephalometric radiographs of the patients were taken using the standardized technique with centric teeth in occlusion and lips in relaxed position. Angular, horizontal and linear measurements were analyzed for the study group and for the control group. We established that in Prader–Willi patients, there is a decrease of the majority of parameters but the degree of this reduction varies widely between patients and clinically typical facies not always have smaller measurements which can be found in an unusual facies. Facial dysmorphism in Prader–Willi patients varies a group ranging from miss proportions that do not alter the facial architecture as regard of facial typology, skeletal class and pattern of development to a severe disturbance of those. There is a degree of clinical heterogeneity between subjects with Prader–Willi syndrome on clinical evaluation and cephalometric study confirms the heterogeneity for this patients. Because the identification of smaller dimensions for majority of parameters in children and adults, the possibility of developmental delay or growth retardation delay can be excluded. These findings are important for the orthodontist for optimum timing of orthodontic management of patients with Prader–Willi syndrome. Keywords: Prader–Willi syndrome, cephalometry, orthodontic management.  I ntroduction Prader–Willi syndrome, a rare genetic condition with an incidence between 1 in 25 000 and 1 in 10 000 live births was first described in literature by Langdon– Down in 1887 [1]. Later, in 1956, Andrea Prader, Heinrich Willi, Alexis Labhart, Andrew Ziegler, and Guido Fanconi reported several cases exhibiting the same phenotype. Ledbetter DH et al., who identified the microdeletion 15q11-13 as being responsible for Prader– Willi syndrome [2], revealed the etiopathogeny in 1981. Prader–Willi syndrome is a complex genetic disorder because there are several genetic models for this condition: microdeletion of paternal chromosome 15q11- 13, uniparental disomy, sporadic mutations, imprinting defects, chromosome translocations, and gene deletions [3–6]. There is a narrow spectrum of facial phenotypic signs, which make the clinical diagnosis difficult in some cases. When the facial pattern associates narrow bifrontal diameter, almond shaped eyes, thin upper lip, downturn corner of the mouth and the patient also presents obesity, severe hypotonia, short stature, hypo- gonadism, hyperphagia, cognitive disabilities and behavior problems the diagnosis of Prader–Willi syndrome can be raised. Holm VA et al. established the clinical diagnostic criteria in 1993, which were later confirmed by Gunay-Aygun M et al. [7, 8]. There are several reports describing the craniofacial appearance of Prader–Willi patients, but there are only a few cephalometric studies for these patients. Until present, there are five reports about the cephalometric and orofacial pattern in Prader–Willi patients. Two studies were done by Meany FJ and Butler MG in 1987, the first presents the anthropometric parameters in Prader–Willi patients and the second described the craniometric variability of those patients [9, 10]. Another study was performed by Schaedel R et al., in 1990, and analyzed the cephalometric parameters for Prader–Willi patients [11]. In 2007, Bailleul-Forestier I et al. studied the orofacial phenotype of 15 patients with Prader–Willi R J M E Romanian Journal of Morphology & Embryology http://www.rjme.ro/