WBR0166
| Author | [[PageAuthor::William J Gibson (Reviewed by Alison Leibowitz)]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Genetics |
| Sub Category | SubCategory::Endocrine |
| Prompt | [[Prompt::A 7-year-old female is brought to her physician by her mother after the mother noticed her daughter began menstruating in the past month. The patient’s history is notable for several bone fractures throughout childhood and a “birthmark” that is pictured from a previous visit below.
|
| Answer A | AnswerA::Increased osteoclastic activity |
| Answer A Explanation | [[AnswerAExp::Osteoporosis involves an imbalance of skeletal resorption and skeletal formation, leading to poor mineralization and skeletal fragility. Increased osteoclastic activity causes osteoporosis.]] |
| Answer B | AnswerB::Decreased mineralization of osteoid |
| Answer B Explanation | [[AnswerBExp::Decreased mineralization of osteoid often results in rickets, which is a softening of the bones in children, potentially leading to fractures and deformity. The predominant cause of rickets is a vitamin D deficiency, but also may result from diets lacking adequate calcium.]] |
| Answer C | AnswerC::Inappropriately increased PTH secretion |
| Answer C Explanation | [[AnswerCExp::In primary hyperparathryroidism, the excessive PTH production often results in osteitis fibrosa cystica.]] |
| Answer D | AnswerD::Increased osteoblastic and osteoclastic activity |
| Answer D Explanation | [[AnswerDExp::Paget's disease of bone is caused by increased bone turnover.]] |
| Answer E | AnswerE::Replacement of bone with fibrous tissue |
| Answer E Explanation | [[AnswerEExp::Polyostotic fibrous dysplasia is a feature of McCune-Albright Syndrome.]] |
| Right Answer | RightAnswer::E |
| Explanation | [[Explanation::McCune-Albright syndrome (polyostotic fibrous dysplasia) is a genetic disorder of bones, skin pigmentation, and hormonal problems characterized by precocious puberty, unilateral cafe au lait spots, and polyostotic fibrous dysplasia. The syndrome can develop at a broad spectrum of severity. McCune-Albright syndrome frequently involves the cranium and facial bones, pelvis, spine, and shoulder girdle. The sites of involvement are the femur (91%), tibia (81%), pelvis (78%), ribs, skull and facial bones (50%), upper extremities, lumbar spine, clavicle, and cervical spine, in decreasing order of frequency. The craniofacial pattern of the disease occurs in 50% of patients with the polyostotic form of fibrous dysplasia. Educational Objective: McCune-Albright syndrome (polyostotic fibrous dysplasia) is a genetic disorder of bones, skin pigmentation, and hormonal problems characterized by precocious puberty, unilateral cafe au lait spots, and polyostotic fibrous dysplasia. |
| Approved | Approved::Yes |
| Keyword | WBRKeyword::McCune-Albright syndrome, WBRKeyword::Endocrine, WBRKeyword::Endocrinology, WBRKeyword::Genetics, WBRKeyword::Mosaicism, WBRKeyword::Somatic |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |
