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

Clinical and radiographic characteristics of pycnodysostosis: A systematic review

Purpose

Pycnodysostosis (PYCD), an autosomal recessive syndrome, is characterized by an imbalance in bone remodeling that produces various clinical and radiographic craniofacial manifestations. This review represents a systematic examination of these manifestations, as well as oral features associated with PYCD.

Materials and Methods

A systematic review was conducted across 8 databases from February to March 2023. The search strategy focused on studies reporting cases of PYCD that examined the clinical and radiographic craniofacial and oral characteristics associated with this syndrome.

Results

The review included 84 studies, encompassing a total of 179 cases of PYCD. More than half of the patients were female (55.3%), and the mean age was 14.7 years. Parental consanguinity was reported in 51.4% of the cases. The most common craniofacial clinical manifestation was a prominent nose, observed in 57.5% of cases. Radiographically, the most frequently reported craniofacial characteristics included the presence of an obtuse mandibular angle (84.3%) and frontal cranial bosses (82.1%). Clinical and radiographic examinations revealed oral alterations, with micrognathia present in 62.6% of patients and malocclusion in 59.2%. Among dental anomalies, tooth agenesis was the most commonly reported, affecting 15.6% of patients.

Conclusion

Understanding the clinical and radiographic craniofacial features of PYCD is crucial for dental professionals. This knowledge enables these clinicians to devise effective treatment plans and improve patient quality of life.

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.

Pyknodysostosis: A case report of an 8-year-old male with a rare genetic disorder

INTRODUCTION AND IMPORTANCE

Pyknodysostosis is a rare genetic disorder characterized by skeletal and craniofacial abnormalities. It is an autosomal recessive disorder caused by mutations in the gene encoding cathepsin K. Pyknodysostosis is associated with short stature, brittle bones, and distinctive facial features.

CASE PRESENTATION

This case report presents the clinical manifestations, diagnostic challenges, and management strategies of an 8-year-old male with pyknodysostosis, an extremely rare genetic disorder characterized by skeletal and craniofacial abnormalities. The patient's clinical presentation, radiographic findings, genetic testing results, and treatment approach are discussed. Additionally, the importance of genetic counseling and multidisciplinary care in managing this condition is emphasized.

CLINICAL DISCUSSION

A multidisciplinary approach involving orthopedics, genetics, dentistry, and psychological support is crucial for managing patients with pyknodysostosis. Regular follow-up visits, careful monitoring of fractures, and appropriate interventions can improve the patient's quality of life and reduce complications.

CONCLUSION

The importance of early recognition, genetic testing, and multidisciplinary care is emphasized for effective treatment and support. Further research is needed to enhance our understanding of this rare genetic disorder and develop targeted therapies.

Clinical, genetic aspects and molecular pathogenesis of osteopetrosis

Osteopetrosis ("marble bone", ICD-10-78.2) includes a group of hereditary bone disorders distinguished by clinical variability and genetic heterogeneity. The name "osteopetrosis" comes from the Greek language: 'osteo' means 'bone' and 'petrosis' means 'stone', which characterizes the main feature of the disease: increased bone density caused by imbalances in bone formation and remodeling, leading to structural changes in bone tissue, predisposition to fractures, skeletal deformities. These defects, in turn, affect other important organs and tissues, especially bone marrow and the nervous system. The disease can be autosomal recessive, autosomal dominant, X-linked or sporadic. Autosomal dominant osteopetrosis has an incidence of 1 in 20,000 newborns and autosomal recessive one has 1 in 250,000. To date, 23 genes have been described, structural changes in which lead to the development of osteopetrosis. Clinical symptoms in osteopetrosis vary greatly in their presentation and severity. The mildest skeletal abnormalities are observed in adulthood and occur in the autosomal dominant form of osteopetrosis. Severe forms, being autosomal recessive and manifesting in early childhood, are characterized by fractures, mental retardation, skin lesions, immune system disorders, renal tubular acidosis. Clinical examination and review of radiographs, bone biopsy and genetic testing provide the bases for clinical diagnosis. The early and accurate detection and treatment of the disease are important to prevent hematologic abnormalities and disease progression to irreversible neurologic consequences. Most patients die within the first decade due to secondary infections, bone marrow suppression and/or bleeding. This article summarizes the current state of the art in this field, including clinical and genetic aspects, and the molecular pathogenesis of the osteopetrosis.