Cephalometric characteristics and dentofacial abnormalities of Pycnodysostosis: report of four cases from Brazil Cristiane Sá Roriz Fonteles, DDS, PhD,a Cauby Maia Chaves, Jr, DDS, PhD,a Adriana Da Silveira, DDS, PhD,b Eduardo Costa Studart Soares, DDS, PhD,a José Luciano Pimenta Couto, DDS,c and Maria de Fátima Vitoriano de Azevedo, MD, MS,d Fortaleza-Ce, Brazil, and Chicago, IL FEDERAL UNIVERSITY OF CEARÁ AND UNIVERSITY OF ILLINOIS CHICAGO Pycnodysostosis (PKND) is a human autosomal recessive genetic disorder characterized mainly by osteosclerosis of the skeleton, severe bone fragility, and short stature. This syndrome usually presents very typical craniofacial deformities, such as beaked nose, micrognathia, hypoplastic midface, open mouth posture, grooved palate, anterior cross-bite, dental crowding, and over-retained deciduous teeth. Early diagnosis and intervention are of the utmost importance. Four cases from the northeast of Brazil are reported including 2 siblings. Features included maxillary retrusion, reduced facial height, open bite, and bone fracture history. Very poor oral hygiene, severe dental caries, and periodontal disease were also present. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2007;104: e83-e90) Pycnodysostosis (PKND) is a rare human genetic disorder characterized mainly by osteosclerosis of the skeleton, severe bone fragility, and short stature (less than 150 cm adult height), first described and named by Maroteaux and Lamy (1962)1 as a separate syndrome. This syndrome constitutes an autosomal recessive inheritance pattern, with equal sex distribution, and parental consanguinity being found in about 30% of reported cases.2-5 The locus for PKND maps to the human chromosome 1q21.6 Common clinical manifestations include increased bone density, frequent fractures, clavicular dysplasia, skull bone deformities with delayed suture closure, acro-osteolysis of the distal phalanges, unossified fontanels, thin and hypoplastic fingernails, proptosis, blue sclera, a beaked or parrot-like nose, and frontal and occipital bossing.1,7 These patients express very specific craniofacial features, with hypoplastic maxilla and flattened mandibular angle being the most commonly reported facial abnormalities. Intraoral examination usually reveals anterior crossbite, posterior open bite, a Associate Professor, Department of Clinical Dentistry, Federal University of Ceará. b Assistant Professor, Department of Orthodontics and The Craniofacial Center, University of Illinois at Chicago. c MS candidate in Dentistry, Federal University of Ceará. d Associate Professor, Department of Pediatric Maternal Health, Federal University of Ceará. Received for publication Dec 4, 2006; returned for revision Apr 9, 2007; accepted for publication May 7, 2007. 1079-2104/$ - see front matter © 2007 Mosby, Inc. All rights reserved. doi:10.1016/j.tripleo.2007.05.011 severe dental crowding, poor oral hygiene, periodontal disease, and grossly decayed teeth. Thus, early identification and genetic counseling is of extreme importance, allowing a reduced number of fractures throughout life. Clinical manifestations of this syndrome are the main source of diagnosis. Comprehensive dental treatment comprising full oral rehabilitation and orthodontic and orthognathic treatment becomes a challenge because of the seriousness of the genetic disorder and multiplicity of the encountered oral diseases. The objective of this article is to report on 4 cases found in the northeast of Brazil, to present their cephalometric characteristics, and to discuss radiological findings and management issues common to these patients. CASE REPORTS Case 1 A 16-year 6-month-old female presented to the Pediatric Special Care Clinic for her first dental evaluation, referred from Clinical Genetics at the Federal University of Ceará (UFC). The patient reported a history of multiple fractures, having been diagnosed with PKND at around 4 years of age, based on clinical manifestations, being the younger of 2 affected siblings. The mother reported observing similar aspects between the younger and the oldest daughter (Case 2) after the first year of life, including that the child was small for her age and only walked and started speaking after age 3 years; both siblings presented similar facial features. Parental consanguinity was not present in these cases. At the examination, the patient had a height of 120 cm and weighed 25 kg. Clinical findings and e83 e84 OOOOE October 2007 Fonteles et al. Table I. Most prominently observed clinical features Clinical findings Frontal bossing Proptosis Convex profile Micrognathia Open mouth posture Protruded tongue Grooved palate Anterior cross-bite Posterior cross-bite Anterior open bite Posterior open bite Dental crowding Retained deciduous teeth Partial anodontia Dental morphology anomalies Poor oral hygiene Dental caries Periodontal disease Case 1 Case 2 Case 3 Case 4 ⫹ ⫹ ⫹ ⫹ ⫹ ⫹ ⫹ ⫹ ⫺ ⫹ ⫹ ⫹ ⫹ ⫹ ⫹ ⫹ ⫹ ⫺ ⫺ ⫹ ⫹ ⫺ ⫺ ⫹ ⫹ ⫺ ⫹ ⫹ ⫹ ⫺ ⫺ ⫺ ⫹ ⫹ ⫹ ⫺ ⫹ ⫹ ⫺ ⫹ ⫹ ⫹ ⫺ ⫺ ⫺ ⫹ ⫹ ⫹ ⫺ ⫺ ⫹ ⫹ ⫺ ⫹ ⫹ ⫹ ⫹ ⫹ ⫺ ⫹ ⫹ ⫹ ⫹ ⫹ ⫹ ⫹ ⫹ ⫹ ⫹ ⫺ ⫹ ⫹ Where, ⫹, presence and ⫺, absence. cephalometric measurements for this and all cases are summarized in Tables I and II and Figs. 1-8. The most common observations on cephalometric analysis were maxillary retrusion with hyperdivergent mandibular growth (SN.GoMe 56.0 mm; MP.FH 40.6 mm), reduced posterior facial height (S-Go 67.1 mm), maxillary transverse deficiency, and lack of vertical growth of the maxilla generating severe openbite (Fig. 1, B). See Table III for cephalometric landmarks and lines. In addition, there was pronounced reduction in SNA (75.8o) and SNB (70.8o) angles, coupled with a severely decreased mandibular (Goc-Me 47.4 mm) and maxillary (ANS-PNS 45.7 mm) body length. There was a reduced superior posterior airway space (SPAS 5.0 mm) and an increased soft palate length. Case 2 This patient was the 21-year 11-month-old female sibling of Case 1, diagnosed with PKND around age 3 years, based on clinical manifestations, including small stature (height, 123 cm, weight, 27 kg; currently, height, 126 cm, weight, 28.5 kg), syndromic features, and multiple fractures of the extremities. Common clinical findings can be seen in Fig. 3, A. Radiographically, a fracture on the right side of the body of the mandible was identified. Clinically, limited mandibular movements and facial asymmetry were observed. The patient described pain on full mouth opening. See Fig. 4 for intraoral findings. Similar to Case 1, cephalometric analysis showed a marked reduction in SNA (70.9o) and SNB (66.4o) angles, associated with a shortened maxillary (ANSPNS 41.1 mm) and mandibular (Goc-Me 47.6 mm) body length. However, SPAS (13.3 mm) and PAS (7.8 mm) (Fig. 3, B) measurements revealed alterations limited to the posterior airway space only, with no reductions being observed in the superior region, when compared with control values. Soft palate length was only slightly enhanced (PNS-P 40.3 mm), whereas soft palate width remained within the normal range. Case 3 This 17-year 7-month-old male patient was referred to the Pediatric Special Care Clinic for dental treatment. Diagnosed with PKND at around age 2 years, the patient had a history consistent with consanguineous parents, recurrent respiratory infections, and respiratory insufficiency until age 5 years. In addition, a history of recurrent fractures as a result of small traumatic episodes was also reported. On clinical examination the patient presented a height of 134.7 cm and a weight of 30.2 kg, brachydactyly (Fig. 6), dystrophic fingernails, and a slightly retrognathic convex profile, as well as other previously described clinical and radiographic typical features of PKND. Multiple congenitally missing permanent teeth, associated with anomalies in dental position and morphology were also observed (Fig. 5). Case 3 was the only patient with altered soft palate dimensions in both length and width (PNS-P 42.7 mm and SoPN 16.8 mm). A tendency toward reduction of the posterior superior airway space (SPAS 8.6 mm) was also appreciated through cephalometric analysis (Table II). Caries, calculus accumulation, gingival retraction, and marginal gingivitis were noticed. Case 4 This 14-year 7-month-old female patient was referred for dental evaluation from the pediatric and genetic ambulatory clinic at the Walter Cantídio University Hospital (HUWC). The mother described first noticing that the child was not growing normally at around 3 months of age. Followed until age 3 years by pediatricians at a local hospital, the child was referred to HUWC for genetic evaluation and counseling, where the syndromic pattern was first identified and a diagnosis was made. No parental consanguinity was present in this case. Past medical history was significant for urinary tract infection at age 1 year, fractured tibia at age 8 years, fractured clavicle at age 10 years, and allergic rhinitis. The patient was receiving pyschologic counseling for panic disorder. On clinical examination the height of 138 cm and a weight of 35 kg were observed. Radiographic hand and wrist evaluation showed malformed epiphyses of the radius, while cephalometric analysis among other typ- OOOOE Volume 104, Number 4 Fonteles et al. e85 Table II. Cephalometric measurements of 4 patients with PKND, with chronological ages of 16 years 6 months (case 1), 21 years 11months (case 2), 17 years 7 months (case 3), and 14 years 7 months (case 4) Sagital measurements SNAo SNBo ANBo Co-A, mm Co-Gn, mm Goc-Me, mm ANS-PNS, mm Vertical measurements SN.GoMe, mm MP.FH, mm AFAI. (ANS.Me), mm Goc-Ar, mm S-Go, mm N-Me, mm Pharyngeal airway space SPAS, mm PAS, mm PNS-P, mm SoPN, mm Control* Case 1 Case 2 Case 3 Case 4 81.4 ⫾ 3.3 79.1 ⫾ 2.6 2.3 ⫾ 1.5 93.6 ⫾ 3.2 121.6 ⫾ 4.5 71.0 ⫾ 5.0 53.0 ⫾ 3.0 75.8 70.8** 5.0 69.5** 92.1** 47.4** 45.7** 70.9** 66.4** 4.5 70.9** 94.6** 47.6** 41.1** 79.3 77.3 2.0 76.4** 97.7** 50.0** 49.0 74.3** 76.9 ⫺2.6** 79.3** 99.5** 60.7** 43.9** 32.0 ⫾ 3.0 25.0 ⫾ 3.0 69.4 ⫾ 5.9 56.0** 40.6** 68.5 65.9** 43.4** 60.7 56.7** 41.5** 52.5** 47.7** 33.7** 48.4** 50.6 ⫾ 5.4 78.8 ⫾ 4.6 124.0 ⫾ 5.3 46.7 67.1** 115.2 42.0 56.8** 111.1** 43.8 59.5** 106.4** 32.2** 50.1** 98.6** 11.0 ⫾ 3.0 11.0 ⫾ 2.0 37.0 ⫾ 2.0 11.0 ⫾ 2.0 5.0** 10.2 41.4** 11.0 13.3 7.8 40.3 10.5 8.6 10.5 42.7** 16.8** 5.0** 13.0 43.7** 12.7 *Control values were based on a sample of young adult patients taken from a population of Brazilian subjects with normal dentition and craniofacial morphology. See Table III for cephalometric landmarks and lines. Where mm, millimeter. **ⱖ two standard deviations. ical features were consistent with a retropositioned maxilla (SNA 74.3o) and mandible (SNB 76.9o), and an anterior-posterior reduction of the maxillary and mandibular bodies (ANS-PNS 43.9 and Goc-Me 60.7 mm) with a class III skeletal pattern of malocclusion. However, in a clinical perspective, the soft tissue profile did not reflect the class III skeletal pattern observed in the previous cases, thus, being clinically described as acceptable (Fig. 7). Pharyngeal airway space measurements demonstrated a significant reduction in the superior posterior region (SPAS 5.0 mm) and an elongated soft palate (PNS-P 43.7 mm), with values 2 standard deviations above controls. Intraoral findings are shown in Fig. 8. DISCUSSION In 1962, Maroteaux and Lamy1 thoroughly described common clinical manifestations involved in this reported syndrome. Since then, the literature has referred to patients with PKND as expressing very specific craniofacial features, including hypoplastic maxilla and mandible, with a highly retrognathic profile, obtuse gonial angle, hypoplastic paranasal sinuses, grooved palate, and dental crowding, followed by overly retained deciduous teeth and delayed eruption of the permanent dentition. Furthermore, a tendency toward the development of severe dental caries and periodontal disease has also been described. Many have reported on clinical and radiological findings associated with this syndrome8-14; however, only a few have added cephalometric measurements to their reports.15,16 Based on cephalometric findings, it was observed in all cases that the maxilla presented reduced dimensions (hypoplastic maxilla), evidenced by Co-A, SNA, and ANS-PNS measurements. The body of the mandible also presented a generalized reduction of its size, which could be more so appreciated on its body by Goc-Me measurements, thus leading to believe that the maxilla would be more involved in the development of the significantly unfavorable skeletal sagittal pattern of these subjects. These findings associated with reduced SNA and SNB angles may strongly influence the posterior pharyngeal airway space. Only significantly reduced in case 4, the ANB angle was not a good predictor of the class III pattern of malocclusion. An appreciably retropositioned maxilla and midface may be a possible explanation for this observed and previously described numeric factor, whereas Hunt et al. (1998),15 while reporting on 3 new cases, identified a negative ANB angle in only 1 case. All studied cases revealed a predominance of vertical growth with an inclined mandibular plane, rotated clockwise (SN.GoMe and MP. FH), with an important influence of a deficient mandibular ramus height e86 Fonteles et al. OOOOE October 2007 Fig. 1. A, Soft tissue profile of Case 1, demonstrating frontal bossing, proptosis, and retrognathic convex soft tissue profile. B, Lateral cephalometric radiograph showing hypoplastic maxilla, thin mandibular bone, flattened gonial angle, hypoplastic coronoid processes and anteroposterior open bite. C, Cephalometric tracing of Case 1, with reference points and lines measured. OOOOE Volume 104, Number 4 Fonteles et al. e87 Fig. 2. Frontal intraoral view of Case 1, demonstrating dental crowding, severe dental caries, and periodontal disease. (Goc-Ar), coupled with a deficient posterior facial height (S-Goc) and compromising pharyngeal airway space. This aspect was more prominently seen in case 1, where clinically a complete open bite was observed. Interestingly, it was noticed that in cases 3 and 4 the soft tissue profile was able to mask the intensity of the radiographically observed craniofacial discrepancies. The AFAI and N-Me measurements representing the anterior-inferior facial height and total anterior facial height, respectively, were significantly reduced, probably attributable to a deficiency on the maxillary vertical length and midface. In addition, an increased length of the soft palate was observed in all reported cases, in spite of the maxillary and mandibular deficiency, along with a reduction of the posterior superior airway space markedly observed in cases 1 and 4. Only case 3 demonstrated alteration in soft palate length and width. These findings have been recently reported by Muto et al. (2005).16 In their study, full cephalometric analysis of 2 edentulous adult patients revealed long soft palate as a common feature. Although this finding agrees with previously reported data,17 several past reports did not show concurrent findings.15,18,19 The authors have hypothesized that long soft palate combined with maxillary and mandibular deficiency and posteriorly situated maxilla would be some of the anatomical features responsible for pharyngeal airway obstruction. Our data concur with this hypothesis, although further studies with a larger number of subjects should be carried out to confirm findings. As a consequence of the severely encountered craniofacial abnormalities, obstructive sleep apnea (OSA) has been reported in patients with PKND, with increased risk of respiratory insufficiency.17 However, in spite of the nonfavorable anatomical features, the Fig. 3. Less severely affected of both siblings (Case 2). A, Lateral clinical appearance showing beaked nose, micrognathia, and midface hypoplasia. B, Lateral cephalometric radiograph with anterior crossbite, maxillary hypoplasia, and mandibular fracture. e88 Fonteles et al. OOOOE October 2007 Fig. 4. Lateral intraoral view of Case 2 showing anterior crossbite, posterior open bite, severe dental crowding, periodontal disease, and grossly decayed teeth. Fig. 6. Hand and wrist radiograph of Case 3 showing shortened terminal distal phalanges on three fingers, a typical feature of PKND. Fig. 5. Panoramic radiograph of Case 3 showing small mandible, partial anodontia, and malpositioned dentition. presently described clinical cases did not manifest clinical signs or symptoms of OSA. Follow-up of these patients and examination of sleep apnea will be encouraged once dental disease is controlled and recalls are established. Currently, no recommendation or information is available in the literature regarding the efficacy and safety of orthodontics in children or even young adults with PKND. Orthodontic and orthopedic movements are fully dependent on osteoclastic activity and bone resorption and remodeling capacities. A deficient activity of the lysosomal cysteine protease cathepsin K has been identified as the cause of this osteopetrotic disease, now classified as a lysosomal disorder.20 Highly expressed in osteoclasts,21 and a key enzyme in the process of bone matrix protein degradation,22,23 deficiency in this enzyme generates osteoclastic dysfunction and reduced bone resorption and remodeling, rendering a net increase in bone mass with a resultant increased generalized osteosclerosis, directly responsible for many of the observed clinical features, probably rendering an orthodontic approach as a nonpromising treatment strategy. Surgery and comprehensive oral rehabilitation are a challenge, since osteomyelitis has been described as a common occurrence in adults with PKND,24,25 therefore surgical intervention should preferably be done earlier in life when risk factors for osteomyelitis development are reduced.26,27 Unfortunately, orthognathic surgery has not been previously described in the literature for these patients, aside from a recent report28 where distraction osteogenesis technique was used in a 15-year-old female patient for correction of a severe midfacial hypoplasia. The authors reported not finding any signs of clinical or radiological relapse after a 13-month follow-up, suggesting this technique as a treatment option for these cases. Unfortunately, these patients searched for care later in life, having missed early childhood prevention of oral disease. Early intervention to relieve dental crowding has been recommended to the pediatric patient to allow better dental alignment and oral hygiene of the OOOOE Volume 104, Number 4 Fonteles et al. e89 Fig. 7. Frontal (A) and lateral view (B) of Case 4 demonstrating acceptable soft tissue profile. Table III. Cephalometric landmarks and lines Sagital measurements SNA SNB ANB Co-A Co-Gn Goc-Me ANS-PNS Vertical measurements SN.GoMe MP.FH AFAL. (ANS.Me) Goc-Ar S-Go N-Me Pharyngeal airway space SPAS PAS PNS-P SoPN Fig. 8. Upper and lower intraoral views of Case 4 showing grooved palate, delayed exfoliation of deciduous teeth (A) and dental crowding (B). Maxillary anterior-posterior position Mandibular anterior-posterior position Maxillary position relative to the mandible Maxillary length Mandibular length Body of the mandible length Body of the maxilla length Cranio base and mandibular body angle Frankfort horizontal and mandibular plain angle Anterior-inferior facial height Mandibular ramus height Total posterior facial height Total anterior facial height Superior posterior airway space Posterior airway space Soft palate length Soft palate width primary and erupting permanent dentition,13 reducing chances of dental impaction, periodontal disease, and dental caries. Because of serious limitations imposed by dentofacial discrepancies, it would be advisable for these patients to be treated as high-risk patients with frequent recall visits in order to prevent dental caries and periodontal disease, providing early intervention if restorative procedures become needed. Currently, the utmost importance is given to the early diagnosis of PKND aiming at prevention of fractures and good quality of life. These patients usually have a e90 OOOOE October 2007 Fonteles et al. normal life span, thus risk factors should be carefully addressed while planning treatment. Symptoms of PKND, such as pharyngeal airway obstruction, development of osteomyelitis, osteosclerosis, fractures, and limited mouth opening with great difficulty in obtaining access for adequate restorative and surgical treatment, highlight the importance of early prevention and intervention. REFERENCES 1. Maroteaux P, Lamy M. La pycnodysostose. Presse Med 1962;70:999-1002. 2. Hou WS, Brumme D, Zhao Y, Mehler E, Dushey C, Weinstein H, et al. Characterization of novel cathepsin K mutations in the pro and mature polypeptide regions causing pycnodysostosis. J Clin Invest 1999;103:731-8. 3. Nishi Y, Atley L, Eyre DE, Edelson JG, Superti-Fuga A, Yasuda T, et al. 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J Oral Maxillofac Surg 1984;42: 819-23. Nørholt SE, Bjerregaard J, Mosekilde L. Maxillary distraction osteogenesis in a patient with pycnodysostosis: a case report. J Oral Maxillofac Surg 2004;62:1037-40. Reprint requests: Cristiane Sá Roriz Fonteles Unidade de Pesquisas Clínicas/Universidade Federal do Ceará Avenida José Bastos, 3390, sala 106 Caixa Postal 3229 CEP 60.436-160 Fortaleza-Ce, Brazil cfontele@ufc.br