Year : 2008 | Volume
: 26 | Issue : 5 | Page : 23--25
Pyknodysostosis: Oral findings and differential diagnosis
LF Soares1, I.P.R Souza1, AS Cardoso1, L Pomarico2,
1 Department of Oral Diagnosis and Oral Pathology, School of Dentistry, Federal University of Rio De Janeiro, Rio de Janeiro, RJ, Brazil
2 Department of Pediatric Dentistry, School of Dentistry, Federal University of Rio De Janeiro, Rio de Janeiro, RJ, Brazil
L F Soares
Rua Visconde de PirajŠ, 4 /306, Ipanema, Rio de Janeiro 22410-000, RJ,
Pyknodysostosis is a rare, genetic, autosomal recessive condition characterized by short stature, generalized bone sclerosis, and oral manifestations such as maxillary atresia and an increase of the mandibular angle. The main purpose of this article was to report a case of pyknodysostosis, describing the characteristic orofacial findings of the disease and discussing the differential diagnosis.
|How to cite this article:|
Soares L F, Souza I, Cardoso A S, Pomarico L. Pyknodysostosis: Oral findings and differential diagnosis.J Indian Soc Pedod Prev Dent 2008;26:23-25
|How to cite this URL:|
Soares L F, Souza I, Cardoso A S, Pomarico L. Pyknodysostosis: Oral findings and differential diagnosis. J Indian Soc Pedod Prev Dent [serial online] 2008 [cited 2020 Feb 17 ];26:23-25
Available from: http://www.jisppd.com/text.asp?2008/26/5/23/41750
Pyknodysostosis is a rare bone dysplasia. The etiology is genetic and transmission is autosomal recessive. It can be associated to consanguinity between the parents in 30% of cases, without predilection for gender. 
The main characteristics of the disease are short stature and bone sclerosis, in addition to retardation or absence of closing of the fontanelles.  The extremities are stunted and height at adult age can vary from 134 to 152 cm.  The terminal phalanges are short and the fingernails hypoplasic. The trunk is not shortened and it is common to see pectus excavatum . There is increased radiopacity of all the bones, mainly of the spinal column, long bones, and cranial base. 
Skeletal alterations include thickening of the cranial base, straight or obtuse mandibular angle, hypoplasia, and lack of pneumatization of the paranasal sinuses. The calvaria is disproportionately large, due to bulging frontal and occipital bones. , The prognosis of the disease is good and no other more serious systemic alteration has been noted. 
The purpose of this article was to report a case of a child with pyknodysostosis and to discuss characteristic orofacial findings of the disease.
A 7-year-old female patient arrived for dental treatment at a pediatric dental clinic of a public university, complaining of atresia of the dental arches and gingival inflammation.
There was no report of abnormalities either during pregnancy or during childbirth. Her medical history revealed that at 5 years of age, the patient had a complete survey in a private medical clinic to investigate growth retardation (without conclusive results, according to her guardian). The patient was only child and did not show disturbances of behavior or sociability. At the time of the appointment, she was attending school at a level compatible with her age group.
The extrabuccal clinical examination showed short stature, narrow shoulders, frontal bulge, and disproportion of the size of her head with face, which was small [Figure 1]. Mouth breathing and atypical swallowing were noted, and during the intrabuccal clinical examination anterior open bite [Figure 2], posterior cross bite, deep palate, mandibular, and maxillary atresia were noted [Figure 3] and [Figure 4]. Generalized gingivitis was observed, with extensive accumulation of biofilm on several tooth surfaces. The child brushed her own teeth once a day, without supervision from any adult.
Lateral teleradiography [Figure 5] showed thickening of the cranial base, a straight mandibular angle, while in the antero posterior (AP). X-rays [Figure 6], absence of closing of the fontanelles was noted. Panoramic radiography showed no lack of permanent dental germs although hypoplasia of the maxillary sinus was noted.
An association of the clinical and radiographic data suggested pyknodysostosis as the most likely diagnosis. The patient was then sent to the University's Pediatric Genetic Clinic, where the diagnosis was confirmed.
Various bone diseases should be considered in the differential diagnosis of pyknodysostosis, particularly cleidocranial dysostosis, acroosteolysis, osteogenesis imperfecta, and osteopetrosis. ,
In cleidocranial dysostosis open fontanelles and cranial sutures are also observed at an advanced age, although in this case the clavicle is also involved, a bone rarely affected in pyknodysostosis. Furthermore, cleidocranial dysostosis is transmitted by autosomal dominant inheritance.  That trait also refers to acroosteolysis, which is associated to stunted body height, kyphosis, absence of frontal sinuses, fusion of vertebral processes, and shortening of the phalanges. The absence of the mandibular angle, which is so characteristic of pyknodysostosis, however, does not occur in acroosteolysis 
Bone fragility and a history of frequent fractures may suggest the possibility of diagnosing osteogenesis imperfecta, although in the latter case it should be borne in mind that the fractures are much more severe. ,
In osteopetrosis there is also a generalized increase of radiopacity of the bones and, as a whole, serious anemia is associated to this characteristics. , Kumar et al , reported a case in which a 6-year-old patient, with the clinical and radiological characteristics of pyknodysostosis, also showed anemia and hepatosplenomegaly, commonly found in osteopetrosis. 
Another craniofacial dysostosis relates to Stanescu's Syndrome of osteosclerosis, in which mandibular underdevelopment occurs, with an increase of the angle, exophtalmos, shortening of limbs, and dense cortices of the long bones, although this is more rare and is autosomal dominant. 
Enamel hypoplasia was mentioned in the literature as one of the alterations commonly found in patients with pyknodysostosis. ,, However, the patient of this report did not present signs of alterations in the enamel or in the shape of her teeth. Furthermore, no alteration was noted in the tooth eruption, differing from the reports of Ferguson et al and Hunt et al , who observed a delay in eruption and ectopy of various permanent teeth. , There is, nonetheless, a severe lack of space due to the underdevelopment of the maxillaries, as noted in the case presented, which can often lead to tooth crowding and impaction. ,,,
It is important with such patients to bear in mind the increased risk of pathological fractures during dental operations and tooth extraction because of bone fragility. However, in spite of the fragility, bone healing is normal.  In the cases reported by Bathi and Masur,  one of the patients presented a history of osteomyelitis related to a tooth with a large carious lesion. The authors also commented that due to osteosclerosis in these patients, osteomyelitis could become refractory. Those findings underscore the importance of diagnosing the anomaly for correct dental planning and treatment of these patients, taking proper precautions.
The patient presented the mouth deformity described by most of the reports, however, as the three cases reported by Hunt et al , presented different types of malocclusion (accentuated overbite, bilateral cross bite, and biprotrusion, respectively), it may be considered that the presentation of the relationship between the arches is variable. 
Child patients with pyknodysostosis should receive special dental care, particularly preventive treatment, because of the group of mouth alterations described, in addition to periodical follow-up of their growth and craniofacial development.
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