During a routine checkup a 70 year old mate is found to have Serum Alkaline Phosphatase three times the upper limit of norrnal. Serum Calcium, Serum Phosphorous and liver function tests are normal. The most likely diagonsis is
**Core Concept**
Elevated Serum Alkaline Phosphatase (SAP) levels can indicate increased bone turnover or cholestasis, but in this scenario, normal liver function tests and serum calcium/phosphorus levels point towards a bone-related cause. The elevated SAP is likely due to increased osteoblastic activity.
**Why the Correct Answer is Right**
The correct answer is related to Paget's disease, a chronic bone disorder characterized by abnormal bone remodeling. In Paget's disease, osteoclasts break down bone tissue at an accelerated rate, followed by osteoblasts depositing new bone tissue in a disorganized manner. This results in an increase in SAP levels due to the enhanced osteoblastic activity. The disease is more common in older adults and often presents with asymptomatic elevated SAP levels, as seen in this patient.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not directly relate to bone pathology, and the normal liver function tests make cholestasis less likely.
**Option B:** This option is incorrect as it is a metabolic bone disease, but it typically presents with normal or low SAP levels due to the imbalance between osteoclastic and osteoblastic activity.
**Option C:** This option is incorrect as it is a type of bone cancer, which would more likely present with a mix of elevated SAP and alkaline phosphatase isoenzymes, and would not typically have normal liver function tests.
**Clinical Pearl / High-Yield Fact**
Paget's disease is often referred to as "osteitis deformans" and can be asymptomatic, but it can lead to complications such as bone pain, deformity, and increased risk of osteosarcoma. It's essential to monitor SAP levels in older adults, especially those with risk factors.
**Correct Answer: C. Osteitis Deformans (Paget's disease)**