Pathological mandibular fracture complicated by osteonecrosis in an adult patient with pycnodysostosis: clinical report and review of the literature.

Pycnodysostosis is an ultra-rare osteosclerotic skeletal disorder characterized by short stature, susceptibly to fractures, acroosteolysis of the distal phalanges, and craniofacial features (frontal bossing, prominent nose, obtuse mandibular angle, micrognathia). Dental abnormalities (delayed eruption of teeth, hypodontia, malocclusion, dental crowding, persistence of deciduous teeth, enamel hypoplasia, and increased caries) are also frequent; due to bone metabolism alteration, the patients have an increased risk for jaw osteomyelitis, especially after tooth extraction or mandible fracture. Other complications are obstructive sleep apnea, endocrine alterations and cytopenia. Pycnodysostosis is caused by biallelic loss of function variants in CTSK gene, coding the lysosomal protease cathepsin K. CTSK is involved in the degradation of bone matrix proteins, such as type I and type II collagen. In pycnodysostosis, this degradation is decreased, leading to increased bone density and bone fragility with pathological fractures and poor healing. We present a clinical report of a female adult patient with typical pycnodysostosis phenotype. At the age of 52 years, she had a pathological spontaneous fracture of the right mandible complicated by osteonecrosis, treated with load bearing osteosynthesis. The direct sequencing of CTSK gene revealed the presence of the pathogenic homozygous variant c.746T>A, (p.Ile249Asn), that confirmed the diagnosis of pycnodysostosis. We also review the literature case series published to date, that suggest to always consider the diagnosis of pycnodysostosis in case of osteosclerosis, even in the absence of brachydactyly or short stature. This report details the natural history of the disease in this patient, from childhood to adulthood, and highlights the importance of a quality of life assessment. In addition, we describe a case of mandibular osteonecrosis and spontaneous fracture in pycnodysostosis, drawing attention on the maxillofacial complications in these patients and on the importance of a personalized follow-up.

Management of long bone fractures in patients with pycnodysostosis.

Pycnodysostosis is a rare genetic condition that leads to generalised bony sclerosis and increased fracture risk. Orthopaedic specialists play a crucial role in managing affected children due to their susceptibility to frequent fractures. We had a case of a middle childhood female patient with pycnodysostosis and a femur fracture. Initially, an attempt using the Titanium Elastic Nailing System was made, but the sclerotic metaphyseal bone made it challenging. So, we opted for a 4.5 mm locked compressive plate, with multiple drill bits as a backup due to potential drill breakage. Though elastic nailing is preferred for paediatric long bone fractures, surgeons must be prepared for extremely sclerotic cortices and a narrow medullary canal when dealing with patients with pycnodysostosis. Open fixation and multiple drill bits in the toolkit are essential to overcome the potential obstacles during the procedure.

Surgical treatment of pycnodysostosis associated with pathological tibial fracture : Case report and review of the literature.

BACKGROUND: Pycnodysostosis is a rare autosomal recessive lysosomal disorder of bone characterized by diffuse skeletal condensation with thickening of the cortex and narrowing of the medullary canal. CASE PRESENTATION: We present the case of a 4-year-old girl diagnosed with pycnodysostosis and associated pathological tibial fracture. The tibia had an absence of medullary canal. Surgery included reduction and reaming of the canal with placement of a 5 mm diameter telescopic growing nail. CONCLUSION: The presentation of pycnodysostosis as tibial fracture is rare and there is limited literature on its management. We showed its approach focusing mainly on the management of the absent medullary canal.

Pycnodysostosis; A Rare Disease Case Report.

Pycnodysostosis is a rare disease with very few reported cased all over the world. It was first described in 1963 by Maroteaux and Lamy. It is also known as Toulouse-Lautrec syndrome, after a French artist, Henri de Toulouse Lautrec. The affected gene, CTSK, was first isolated in 1996. It is an autosomal recessive osteochondrodysplasia, characterized by disrupted function of osteoclasts. Incidence of this disease is 1.7 per 1 million births with a male to female ratio of 1:1 30% cases arise from consanguineous marriages.

Clinical and genetic characterization of three Russian patients with pycnodysostosis due to pathogenic variants in the CTSK gene.

BACKGROUND: Pycnodysostosis (PD, OMIM # 265800) is a rare variant of skeletal dysplasia with an autosomal recessive type of inheritance, characterized by a combination of specific features such as disproportionate nanism, generalized osteosclerosis, and distinct craniofacial dysmorphism. Radiographic features include acro-osteolysis of the distal phalanges in association with sclerosing bone lesions with multiple fractures. The polymorphism of the clinical manifestations of pycnodysostosis and low prevalence of the disorder lead to the difficulties with early. METHODS: The following tests were used for diagnostics: genealogical analysis, clinical examination, neurological examination according to the standard method with an assessment of the psychoemotional sphere, radiological analysis, searching for pathogenic variants in the CTSK gene by the automated Sanger sequencing. RESULTS: We describe first clinical and genetic characteristics of three Russian patients with pycnodysostosis from unrelated families. Two patients have a novel homozygous nucleotide substitution c.746T>A (p. Ile249Asn), and one has a previously described homozygous pathogenic variant c.746T>C (p.Ile249Thr) in the CTSK gene. In all three cases, a transition or transversion was found at nucleotide position 746 in exon 6 of the CTSK gene, leading to two different amino acid substitutions in the polypeptide chain. The obtained results may indicate the presence of a major pathogenic variant in the CTSK gene, leading to the typical manifestation of the disease. CONCLUSION: The data presented in the study enlarge the clinical, radiological, and mutational spectrum of pycnodysostosis. Typical clinical manifestations and the small size of the CTSK gene make the automated Sanger sequencing the optimal method for diagnosis of pycnodysostosis.

Obstructive sleep apnoea in pycnodysostosis: A three-dimensional upper airway analysis.

AIM: To assess the upper airway (UA) morphology in patients with pycnodysostosis with a 3D analysis, compare results with normative data and investigate the correlation of the total volume (TV) with other UA morphology variables. MATERIALS AND METHODS: Cone beam computed tomography (CBCT) images of eight Danish patients with pycnodysostosis (4 males and 4 females with a mean age of 31.8 years, SD: 16.3 years) were analyzed using Mimics® (Materialise® ) and compared with a sex- and age-matched control group (6 males and 8 females with a mean age of 33.6 years, SD: 18.6 years). RESULTS: The distance from the tip of the epiglottis (E) to the Frankfurt horizontal plane (Fp) was significantly shorter in the pycnodysostosis group (P < .042). Regarding the cross-sectional measurements, at the 'maximum constriction' (P < .005), the 'upper airway limit' (P < .001) and the 'lower airway limit' (P < .035) cross-sections were significantly smaller in the pycnodysostosis group. The volumes 'nasopharynx' (P < .002) and 'total airway' (TV) (P < .01) were also significantly smaller. CONCLUSION: Patients with pycnodysostosis have a reduced total airway as well as nasopharyngeal volume compared with matched controls. Additionally, they have a reduced cross-sectional area in the upper and lower borders of the UA, and the area of maximum constriction is also reduced. These factors might explain the high prevalence of obstructive sleep apnoea in pycnodysostosis. Total airway is positively correlated with total length and cross-sections at all levels including the maximum constriction area as well as the anteroposterior dimension at the upper and lower airway borders.

Genetic and Molecular Evaluation: Reporting Three Novel Mutations and Creating Awareness of Pycnodysostosis Disease.

Pycnodysostosis is a rare autosomal recessive disorder with characteristic diagnostic manifestations. This study aims to phenotype and provide molecular characterization of Egyptian patients, with emphasis on identifying unusual phenotypes and raising awareness about pycnodysostosis with different presentations to avoid a mis- or under-diagnosis and consequent mismanagement. We report on 22 Egyptian pycnodysostosis patients, including 9 new participants, all descending from consanguineous families and their ages ranging from 6 to 15 years. In addition, prenatal diagnosis was performed in one family with affected siblings. They all presented with short stature, except for one patient who presented with pancytopenia as her primary complaint. Moreover, 41.2% of patients had sleep apnea, 14% presented with craniosynostosis, and 44.4% had failure of tooth development. Molecular analysis via direct exome sequencing of the cathepsin K gene revealed three novel mutations ((NM_000396.3) c.761_763delCCT, c.864_865delAA, and c.509G>T) as well as two previously reported mutations among nine new cases. The following is our conclusion: This study expands the molecular spectrum of pycnodysostosis by identifying three novel mutations and adds to the clinical and orodental aspects of the disease. The link between the CTSK gene mutations and the failure of tooth development has not been established, and further studies could help to improve our understanding of the molecular pathology.

Pycnodysostosis: a case report and literature review concerning oral and maxillofacial complications and their management.

OBJECTIVE: There is a lack of knowledge regarding pycnodysostosis (PYCD), which is commonly misdiagnosed as other, similar malformations. This study aims to report a patient with PYCD and conjointly present a comprehensive literature review regarding oral complications after oral surgery procedures. STUDY DESIGN: This study aims to report a noteworthy case of a 40-year-old woman with PYCD who suffered from a midface defect after iatrogenic fracture during extraction of the upper right molars. A comprehensive electronic search was carried out in January 2020 for detection and analysis of the most commonly encountered dentoalveolar PYCD-related complications. The study was granted an exemption from the local institutional review board. RESULTS: The electronic search yielded 35 articles reporting 41 PYCD cases with 62 various reported dentoalveolar complications. The survey reported a prevalence of osteomyelitis (n = 39) followed by pathologic fracture (n = 17), iatrogenic fracture (n = 5), and oronasal communication (n = 1). CONCLUSIONS: This study advocates handling patients with PYCD with care through the use of extensive clinical and radiographic examinations, giving priority to any conservative treatment modalities, atraumatic surgical procedures, prophylactic antibiotic prescriptions, and a regular follow-up schedule to tackle any anticipated complications.

The genotypic and phenotypic spectrum of pycnodysostosis in Saudi Arabia: Novel variants and clinical findings.

Pycnodysostosis is characterized by short stature, osteosclerosis, acro-osteolysis, increased tendency of fractures, and distinctive dysmorphic features. It is a rare autosomal recessive disease caused by biallelic CTSK mutations. The clinical details of 18 patients from Saudi Arabia were reviewed. Short stature, osteopetrosis, acro-osteolysis, and distinctive facial dysmorphism were documented in all cases. Our results highlight the significant complications associated with this disease. The large anterior fontanelle is one of the cardinal signs of this disease; however, half of our patients had small fontanelles and a quarter had craniosynostosis, which caused optic nerve compression. Sleep apnea was of the major complications in three patients. Bone fracture can be a presenting symptom, and in our patients it mainly occurred after the age of 3 years. Bone marrow suppression was seen in a single patient of our cohort who was misdiagnosed initially with malignant osteopetrosis. In this study, we also describe two novel (c.5G > A [p.Trp2Ter], c.538G > A [p.Gly180Ser]) and two reported (c.244-29 A > G, c.830C > T [p.Ala277Val]) CTSK mutations. Our results indicate that the recurrent intronic variant, c.244-29 A > G is likely to be a founder mutation, as it was found in 78% (14/18 patients) of our cohort belonging to the same tribe.

Phenotypic and genotypic spectrum of CTSK variants in a cohort of twenty-five Indian patients with pycnodysostosis.

BACKGROUND: Pycnodysostosis is an autosomal recessive skeletal dysplasia with easily recognizable clinical features and marked molecular heterogeneity. In this study, we explored the clinical and molecular spectrum of 25 Indian patients with pycnodysostosis from 20 families. METHODS: Clinical information was collected on a predesigned clinical proforma. Sanger method was employed to sequence all the exons and exon/intron boundaries of the CTSK gene. Novel variants were systematically assessed by prediction softwares and protein modelling. The pathogenicity of variant was established based on ACMG-AMP criteria. An attempt was also made to establish a genotype-phenotype correlation and devise a diagnostic scoring system based on clinical and radiological findings. RESULTS: Consanguinity and positive family history were present in 65% (13/20) and 45% (9/20) of the families respectively. Short stature and fractures were the predominant presenting complaints and was evident in 96% (24/25) and 32% (8/25) of affected individuals respectively. Gestalt facial phenotype and acro-osteolysis were present in 76% (19/25) and 82.6% (19/23) of the individuals respectively. Hepatosplenomegaly was present in 15% (3/20) of the individuals with one of them having severe anaemia. Causative sequence variations were identified in all of them. A total of 19 variants were identified from 20 families amongst which 10 were novel. Homozygous variants were identified in 90% (18/20) families. Amongst the novel variants, there was a considerable proportion (40%) of frameshift variants (4/10). No significant genotype-phenotype correlation was noted. Scoring based on clinical and radiological findings led to the proposal that a minimum of 2 scores in each category is required in addition to high bone density to diagnose pycnodysostosis with certainty. CONCLUSION: This study delineated the genotypic and phenotypic characterisation of Indian patients with pycnodysostosis with identification of 10 novel variants. We also attempted to develop a clinically useful diagnostic scoring system which requires further validation.

Increased Bone Resorption during Lactation in Pycnodysostosis.

Pycnodysostosis, a rare autosomal recessive skeletal dysplasia, is caused by a deficiency of cathepsin K. Patients have impaired bone resorption in the presence of normal or increased numbers of multinucleated, but dysfunctional, osteoclasts. Cathepsin K degrades collagen type I and generates N-telopeptide (NTX) and the C-telopeptide (CTX) that can be quantified. Levels of these telopeptides are increased in lactating women and are associated with increased bone resorption. Nothing is known about the consequences of cathepsin K deficiency in lactating women. Here we present for the first time normalized blood and CTX measurements in a patient with pycnodysostosis, exclusively related to the lactation period. In vitro studies using osteoclasts derived from blood monocytes during lactation and after weaning further show consistent bone resorption before and after lactation. Increased expression of cathepsins L and S in osteoclasts derived from the lactating patient suggests that other proteinases could compensate for the lack of cathepsin K during the lactation period of pycnodysostosis patients.

Three-dimensional analysis of craniofacial morphology in patients with pycnodysostosis.

OBJECTIVE: To perform a 3D cephalometric analysis of the craniofacial characteristics of patients with pycnodysostosis and compare this with a matched control group. SETTING AND SAMPLE POPULATION: This cross-sectional descriptive study assessed eight CBCTs obtained in patients with pycnodysostosis (4 males, 4 females, mean age: 31.8 years). MATERIALS AND METHODS: Eight Danish patients with pycnodysostosis were seen at the University's Orthodontic Clinic. All CBCTs were analysed using the Mimics 21.0 software (Materialise®, Belgium) and compared with a control group (6 males, 8 females, mean age: 33.6 years). RESULTS: Interclass correlation coefficient showed excellent intra-rater reliability (> 0.93). All measurements in the 3D cephalometric analysis revealed statistical significance (P < .05) when compared with controls. Patients with pycnodysostosis generally had significantly smaller maxilla in the transverse (P < .001), sagittal (P < .002) and vertical (P < .001) dimensions. Their mandibles were also smaller vertically (P < .001) and in length (P < .001). Gonial angle was significantly larger than controls (P < .001), while mandibular volumes were considerably smaller (P < .001). CONCLUSION: Patients with pycnodysostosis have significantly smaller jaws in the vertical, sagittal and transverse dimensions compared with controls. Furthermore, the gonial angle was significantly larger, while the volume of the mandible was significantly smaller.

Osteomyelitis of the jaws in patients with pycnodysostosis: a systematic review.

INTRODUCTION: Pycnodysostosis is a rare autosomal recessive syndrome that provides the abnormal bone metabolism that increases the susceptibility of patients to develop osteomyelitis. OBJECTIVE: This systematic review was conducted to analyze the risk factors associated with the development of complications in the jaws (fractures and osteomyelitis), as well as their clinical-pathological characteristics and therapeutic approaches in patients with pycnodysostosis. METHODS: Searches were performed in the PubMed, Web of Science, Scopus, Lilacs, and Cochrane databases. Case reports or case series that met the eligibility criteria according to the PRISMA statement were included. The full texts of 31 articles were retrieved. Twenty of these articles published between 1969 and 2018 were selected, which described 26 cases of osteomyelitis in patients with pycnodysostosis. RESULTS: The mean age of the patients was 37.84 years; the male-to-female was 1.36:1. The mandible was the most affected site (76.9%). Tooth extraction was the main risk factor for osteomyelitis (61.5%), followed by infection (26.8%) and mandibular fracture (23.0%). Antibiotic therapy alone or combined with some surgical procedure was the treatment used in most cases (80.7%). CONCLUSION: The findings of this review showed that patients with pycnodysostosis are more likely to develop osteomyelitis of the jaws after surgical procedures, especially tooth extraction which remains the main risk factor for its establishment. In addition, prophylactic antibiotic-therapy in the pre- and postoperative periods may prevent the development of osteomyelitis in pycnodysostosis.

Clinical and genetic evaluation of Danish patients with pycnodysostosis.

BACKGROUND: Pycnodysostosis is a rare autosomal recessive osteosclerotic skeletal dysplasia caused by variants in the cathepsin K gene (CTSK). Clinical features include short stature, bone fragility, characteristic facial features and acro-osteolysis of the distal phalanges. Usually, patients suffer from multiple bone fractures. The purpose of this study was to describe the Danish population of pycnodysostosis patients with respect to genotype, phenotype and the prevalence of complications. We collected medical history, performed clinical examination, collected blood- and urine samples, performed dual-energy x-ray absorptiometry scan (DXA) and high-resolution peripheral quantitative computed tomography scan (HRpQCT) and obtained clinical photos. Information about complications, bone mineral density and bone markers in the blood were collected and analysed. RESULTS: Ten patients with a median age of 32 years ranging from five to 51 years participated. The pycnodysostosis phenotype varied with respect to the number of bone fractures and degree of complications. DXA and HRpQCT showed high bone mineral density. A tendency of growth hormone treatment escalating growth and increasing final height was seen. A marker of bone resorption measured in blood was within normal range in nine patients and elevated in one patient. A novel pathogenic variant in CSTK causing pycnodysostosis was detected in two related patients. Moreover information about the patients' own health perception was reported. An example being they rated their mental health to be good despite multiple bone fractures. CONCLUSION: This study provides information about genotypes and phenotypes in a Danish pycnodysostosis population. It reports new data about the complications such as bone fractures and it elucidates the levels of bone turnover markers as well as the density of the bones in one of the biggest cohort of pycnodysostosis patients ever published. An individualised approach to treatment in this patient group is necessary as the phenotype including complications varies between patients. Additional studies are needed to further understand genotype-phenotype correlations.