Background:Osteogenesis imperfecta (OI), is a rare hereditary disease characterized by bone fragility and low bone mass. The clinical presenatation is various with varying severity skeletal signs and inconstant extra-skeletal signs. Type 1 is the most common form (60% of cases).Objectives:Our objective is to describe the various clinical features observed over a period of 15 years.Methods:This is a retrospective descriptive study including 12 patients followed for OI, hospitalized in the Rheumatology Department at Fattouma Bourguiba Hospital Monastir TUNISIA between 2006 and 2019. Files were collected and analyzed.Results:They are 9 boys and 3 girls with an average age of 14.9 ± 8.6 years. Consanguinity was reported in 25% of cases. The reason leading to consultation was, recurrent fractures (75%), blue sclera (16.7), and bone deformity (8.3%). The number of previous fractures was on average of 5, all of which were caused by a low energy trauma. Similar family cases were noted in 41.6%. The mean age of the first fracture was 4.41 ± 3.2 years. The most frequent fracture sites were respectively: femur (7/12), leg (6/12), tibia (3/12), humerus (4/12), ankle (2/12), and forearm (2/12). A deformity was noted in 58.3% of the cases: lumbar kyphosis (2), exaggerated dorsal kyphosis (2), femurs in parenthesis (2), and an anarchic deformity of 2 lower limbs (1). Imperfect dentinogenesis was found in 8.3% of cases, while ENT examination revealed conductive and sensorineural hearing loss in 2 patients each. The main radiological abnormalities were diffuse bone demineralization (9 patients), cortical thinning (5 patients), vertebral compression (3 patients), and fracture (2 patients). The bone densitometry showed a mean Z score of 3.49±1.4 in the lumbar spine. The average serum calcium level was 2.38±1.15, alkaline phosphatases were elevated in all cases with an average of 756±624.9. The vitamin D level was deficient in all cases with an average of 22.75±5.3. All patients received in addition to the vitamin-calcium supplementation, pamidronate intravenously at a dose of 9mg/kg/year with a mean number of 6 cures. The main side effects observed during the infusion were abdominal pain, polyarthralgia and asthenia (1 patient), chest pain (1 patient) and fever and chills (1 patient). The control bone densitometry showed a mean Z score of 1.81±1.2 in the lumbar spine.Conclusion:Despite advances in the OI diagnosis and treatment, more research is needed. Bisphosphonate treatment decreases long-bone fracture rates, but such fractures are still frequent. New antiresorptive and anabolic agents are being investigated but efficacy and safety of these drugs, especially in children, need to be better established before they can be used in clinical practice.References:[1]https://doi.org/10.1097/med.0000000000000367Disclosure of Interests:None declared