Osteogenesis imperfecta (OI) is a rare genetically determined disease with a wide phenotypic spectrum. The typical clinical manifestation affects mainly the skeletal system. Due to the fact that the mutation causing the disorder is located in the gene coding collagen, OI is classified as a connective tissue disease. Children with osteogenesis imperfecta have low bone mass, they also present an increased susceptibility to fractures of the long bones and the spine, as well as bone deformities. Extra-articular manifestations of OI include blue-coloured sclerae, conductive/receptive hearing loss, malocclusion, dentinogenesis imperfecta-type teeth, pulmonary dysfunction, heart valve defects, muscle weakness and ligamentous laxity (1).
In osteogenesis imperfecta, the severity of the disease varies from a slight increase in susceptibility to bone fracture to death in the perinatal period. In 1979, Sillence et al. proposed a classification into four groups (2). Due to the increasing possibilities of molecular diagnostics, further types associated with mutations in genes other than COL1A1 and COL1A2 were discovered (3). The diagnosis is made after collecting the patient's medical history, a thorough physical examination, relevant radiological examinations and assessment of bone mineral density. Evaluation of calcium-phosphate balance is also helpful (4). The final confirmation of the diagnosis is obtained after genetic testing (5). It is also necessary to exclude other possible causes of the presented phenotype, such as secondary decrease of bone mineral density. All types of the disease share an increased susceptibility to bone fractures. To systematise the clinical forms of congenital bone fracture, in 2015 Van Dijk and Sillence proposed a classification limited to five disease types based on the number of fractures and the presence of other symptoms (5):
Type I - Low bone mass is observed, fractures do not occur immediately after birth. There also tends to be an increasingly high incidence of long bone fractures with age. Individuals present bluish-grey colouring of the sclerae and have a high risk of hearing impairment. Bone deformities and signs of dentinogenesis imperfecta are rare.
Type II - Large skeletal deformities are more likely to occur and may be detected already on foetal ultrasound around the 18th -20th week of pregnancy. Fractures of the long bones and ribs are seen intrauterine examination. In this group of patients, there is a high perinatal mortality rate. Ninety percent of the children do not live past the age of four.
Type III - There occurs a significantly reduced bone mass, a high number of fractures as well as progressive bone deformities. Fractures are frequently present at birth. Patients affected by this type of the disease may demonstrate features of dentinogenesis imperfecta and blue-coloured sclerae which become increasingly white with age. A majority of the patients/the group are diagnosed with short stature and may develop features of hearing loss in the future.
Type IV - Recurrent fractures are observed, bone deformities are varied. Most of the patients do not present blue sclerae and hearing loss is rarely observed.
Type V - Patients present a moderate to high tendency for bone fractures with calcification of the interosseous membrane in the forearm, which may lead to secondary dislocation of the radial bone head. Features of dentinogenesis imperfecta and blue staining of the sclerae do not occur.
Symptomatic therapy of osteogenesis imperfecta is aimed at reducing the number of fractures, alleviating pain, improving mobility and motor abilities (6). Due to the multisystem clinical manifestation of the disease, patients require multidisciplinary care, i.e., intensified rehabilitation, sometimes orthopaedic surgery, dental, cardiological, ophthalmological consultations, hearing tests (7). Patients should receive vitamin D3 in a dose adjusted to its blood serum level, sometimes additional calcium supplementation is also recommended. Bisphosphonates (BSF- pamidromate, risedronate, zoledronate) are currently considered to be the gold standard of osteogenesis imperfecta therapy (8). Bisphosphonates inhibit osteoclast activity and induce their apoptosis (3). As a result, bone mineral density increases and the number of fractures is reduced.
The aim of our study is to present selected anthropometric parameters (body weight, height, BMI) in children with different types of osteogenesis imperfecta.