Pycnodysostosis is an autosomal-recessive disorder in which osteoclast dysfunction causes osteosclerosis.7
The incidence of this anomaly is estimated to be 1.7 per 1 million births.3
It is believed that the first case description of pycnodysostosis was in 1923 by Montanari; however, Maroteaux and Lamy defined the characteristic features of pycnodysostosis in 1962.3
General features include short stature (less than 150 cm), generalized diffuse osteosclerosis with a tendency for fracture after minimal trauma, and hypoplastic clavicles.3,4
Cranial and maxillofacial features include prominent eyes with blue sclerae, relative proptosis, beaked nose, frontoparietal bossing, open fontanelles and cranial sutures, hypoplastic paranasal sinuses, and an obtuse mandibular gonial angle, often with relative prognathism.3,4,8
These findings were in agreement with the present case report. Norholt et al9
stated that these patients often present a Class III dentition owing to the maxillary hypoplasia.
Intraoral features include persistence of deciduous teeth with premature or delayed eruption of the permanent teeth, which can cause crowding. In addition, tooth misalignment, enamel hypoplasia, and a grooved palate have been observed.3,4
Dental abnormalities such as hypoplasia of the enamel, obliterated pulp chambers, and hypercementosis are some of the most striking features in this anomaly. Additionally, dental crowding associated with extensive caries and periodontitis is frequently observed.5
Dental crowding impedes correct oral hygiene for the patients with pycnodysostosis. In the present study, although persistence of deciduous teeth was not observed, the congenital absence of many permanent teeth and peg-shaped lateral incisors were observed.
Many studies in literature have reported on clinical and radiological findings,10–13
and diagnostic features16–18
associated with this syndrome. However, only the present study has incorporated all of these factors and included cephalometric measurements of the patient compared with Turkish cephalometric norms.
In the present cephalometric findings, a hypoplastic maxilla and mandible were observed, evidenced by SNA, SNB, and Go-Me measurements, respectively. It is believed that the maxilla would be more involved in the development of the significantly undesirable sagittal skeletal pattern of these subjects. These findings associated with decreased SNA and ANB angles may strongly influence the Class III pattern of malocclusion. A highly retropositioned maxilla may be a possible explanation for this observed and previously described numeric factor,4,15
which was identified as a negative ANB angle in the present case. Interestingly, the soft tissue profile was able to mask the intensity of the radiographically observed skeletal Class III malocclusion.
In addition, this case showed a vertical growth with increased SN-GoMe and FH-MP angles, with an important influence from a deficient posterior facial height (S-Go). The N-Me measurements, representing the total anterior facial height, were also significantly reduced. Findings similar to these have been recently reported by Fonteles et al15
Some features of pycnodysostosis are similar to the more common disorders of osteopetrosis and cleidocranial dysostosis.7
Therefore, pycnodysostosis must be distinguished from osteopetrosis and cleidocranial dysostosis. Emami-Ahari et al17
reported the comprehensive diagnostic features of these anomalies. Osteopetrosis is a dominant trait, which is characterized by generalized increased bone density. The malignant forms are recessive, in which there is severe aplastic anemia caused by the obliteration of the medullary canals and early death.19
Cleidocranial dysostosis is an inherited autosomal dominant disorder and is characterized by a usually normal stature and normal texture of bones except for an increased density of the base of the skull in some cases.20
Pycnodysostosis is an autosomal recessive anomaly and affected individuals have characteristic facies, beaked nose, blue sclera, short stature, aplasia of the digits, generalized increase in the density of bones even though not sufficient to obliterate medullary canals or cranial passages, abnormal dentition, and bone healing at a normal rate with normal blood findings.17
In pycnodysostosis and cleidocranial dysostosis, exposed fontanelles and cranial sutures are observed at an advanced age,21
although in the present case the glass-bone disease was also observed-a bone abnormality rarely seen in pycnodysostosis.
There is no specific treatment for this anomaly and the current treatment is only supportive. Recommendations or information about the effective and reliable orthodontic treatment of children or young adults with pycnodysostosis is not available in the literature.15
Orthodontic and orthopedic movements are dependent on osteoclastic activity, bone resorption, and remodeling capacities.15
Although some authors propose early treatment using orthodontic methods, others argue that the lack of bone remodeling would impede satisfactory results; hence, planned extractions would be more suitable.10
Tooth extraction in patients with pycnodysostosis is carried out during surgery as atraumatically as possible to reduce the risk of fracture, especially in the mandible.5
However, post-extraction osteomyelitis may develop because of the increased bone density.22
Treatment of osteomyelitis in individuals with pycnodysostosis is difficult and may lead to large resections.3,9
Norholt et al9 have defended the orthognathic correction by using a distraction osteogenesis technique. However, the most important orthopedic problem for orthognathic correction is the high infection rates and the recurrent pathological fracture of bones owing to the limited quality and vascularity of the sclerotic bone.3