MSK

Low serum calcium

Low serum Phosphate

Elevated PTH (parathyroid hormone)

Elevated Alkaline Phosphate

Active vitamin D is responsible for raising serum calcium and phosphate levels by acting on the kidney (↑ reabsorption of calcium and phosphate), intestine (↑ absorption of calcium and phosphate) and bone (↑ resorption of calcium and phosphate). Thus if vitamin D is reduced, serum calcium and phosphate will also be reduced. Parathyroid hormone (PTH) is increased to compensate for the low calcium level. Alkaline phosphatase is increased as there is osteoblast hyperactivity- osteoblasts produce osteoid but there is defective mineralization of the osteoid and the mineralization is needed to form bone, so there is an excess of osteoid

Colchicine 

inhibits microtubule polymerization by binding tubulin. This impairs neutrophil chemotaxis and degranulation. In acute gout, monosodium urate crystals are deposited in joint generating an inflammatory response. Colchicine can therefore treat this condition by reducing inflammation by impairing neutrophil response. Other drugs used for acute treatment are glucocorticoids and NSAIDs (e.g. naproxen).

Allopurinol, febuxostat and probenecid are chronic gout drugs (preventative).

In achondroplasia, there is poor endochondral bone formation but intramembranous bone formation is unaffected.

Endochondral bone formation is the mechanism by which long bones grow, cartilage matrix is formed and is then replaced by bone.

However, in intramembranous bone formation, the mechanisms by which flat bones grow (e.g. rib cage, skull) there is no pre-existing cartilage matrix.

Note that growth hormone and insulin-like growth factor 1 levels are normal in this disease.

minimal sun exposure

Poor diety

malabsorption

Liver or renal disease

Osteogenesis imperfecta is also known as ‘brittle bone disease’.

It is a congenital defect of bone formation.

Clinical findings include multiple pathologic fractures (often child abuse suspected), blue sclera due to thin scleral collagen revealing the underlying choroidal veins and deafness due to fracture of bones in the middle ear.

Paget's disease is possibly caused by a paramyxovirus infection of the osteoclasts of the affected bone. It can be monostotic or polyostotic.

It is characterized by an imbalance between osteoclasts and osteoblasts. There are 3 phases- an osteoclastic phase, a mixed osteoclasticosteoblastic phase followed by an osteoblastic phase.

This will result in abnormally thick bone that fractures easily. Biopsy shows the ‘mosaic pattern of lamellar bone’ which resembles puzzles pieces put together.

Clinical findings include bone pain, lion-like facies, hearing loss and increasing hat size.

The complications are osteosarcoma as osteoblasts can get mutated in the disorder and high output cardiac failure as AV shunts are formed in the bone.

Paget's disease is possibly caused by a paramyxovirus infection of the osteoclasts of the affected bone. It can be monostotic or polyostotic.

It is characterized by an imbalance between osteoclasts and osteoblasts. There are 3 phases- an osteoclastic phase, a mixed osteoclasticosteoblastic phase followed by an osteoblastic phase.

This will result in abnormally thick bone that fractures easily. Biopsy shows the ‘mosaic pattern of lamellar bone’ which resembles puzzles pieces put together.

Clinical findings include bone pain, lion-like facies, hearing loss and increasing hat size.

The complications are osteosarcoma as osteoblasts can get mutated in the disorder and high output cardiac failure as AV shunts are formed in the bone.

Rheumatoid arthristis is a systemic and autoimmune disorder associated with chronic joint inflammation. HLA-DR4 link.

An important clinical feature to distinguish it from osteoarthritis is the morning stiffness that improves with use.

With osteoarthritis, a degenerative joint disease, the joint stiffness worsens during the day.

An osteosarcoma is a malignant proliferation of osteoblasts. The clinical features include bone pain with swelling. It is prevalent in teens and the elderly. Risk factors include Paget's disease, familial retinoblastoma and radiation. It usually manifests in the region of the knee. Imaging reveals the Codman triangle and sunburst appearance.

A patient presents with a heliotrope rash, a malar rash and Gottron's papules on the elbows and knees.

She cannot comb her hair or climb the stairs due to muscle weakness. Lab results show an increased creatine kinase, positive antinuclear antibody (ANA) and anti-Jo-1 antibody.

Biopsy reveals perimysial inflammation with perifascicular atrophy. She is treated with corticosteroids.