This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
[{'content': 'According to Sillence classification of osteogenesis imperfecta, most common and mildest form is: \nSelect and explain. \nA. Type 1, B. Type 2, C. Type 3, D. Type 4', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Physical features can vary depending on the type. It forms the\xa0basis for Sillence classification.\nType I: Osteogenesis imperfecta\nThis is the most common and mildest form. In subtype A,\xa0dentinogenesis imperfecta is absent, while in subtype B,\xa0dentinogenesis imperfecta is present. Symptoms of both\xa0subtypes include blue sclera, in utero fractures in 10% of\xa0patients (fractures are more common during infancy),\xa0mild-to-moderate bone fragility with frequency of fractures\xa0decreasing after puberty, kyphoscoliosis, hearing loss, easy\nbruising and short stature.\nType II: Osteogenesis imperfecta\nOsteogenesis imperfecta type II exhibits extreme bone\xa0fragility and frequent fractures. In utero fractures are present\xa0in 100% of cases. Many are stillborn, and 90% die before four\xa0weeks of age. Blue sclera may be present. Hearing loss is not\xa0common to type II\xa0OI. Dentinogenesis imperfecta may be\xa0present along with small nose, micrognathia and short trunk.\nType III: Osteogenesis imperfecta\nType III is associated with dentinogenesis imperfecta, sclera\xa0of variable hue, limb shortening and progressive deformities,\xa0triangular facies with frontal bossing and pulmonary\xa0hypertension. In utero fractures occur in 50% of cases. The\xa0remaining half of the cases have fractures in the neonatal\xa0period. No hearing loss has been reported in this type.\nType IV: Osteogenesis imperfecta\nIn subtype A, dentinogenesis imperfecta is absent, while in\xa0subtype B, dentinogenesis imperfecta is present. Symptoms of\xa0both subtypes include normal sclera, normal hearing,\xa0fractures that begin in infancy (in utero fractures are rare) and\xa0mild angulation and shortening of long bones. Bleeding\xa0diathesis have not been reported in this type.', 'role': 'assistant'}]