Page 604 - Concise Pathology for Exam Preparation ( PDFDrive )

21 Musculoskeletal System 589

Q. Enumerate the commonly encountered metabolic and endocrine
diseases of bone.
Ans. Common metabolic and endocrine bone diseases include
• Osteoporosis: Quantitative reduction in otherwise normal bone.
• Osteomalacia and rickets: Qualitative abnormality due to impaired bone mineralization
because of deficiency of vitamin D in adults and children.
• Scurvy: Defect in collagen formation caused by the deficiency of vitamin C.
• Hyperparathyroidism: Condition in which increased parathyroid hormone (PTH)
leads to osteitis fibrosa cystica (OFC).
• Renal osteodystrophy: Condition associated with chronic renal failure which results in
osteitis fibrosa cystica, osteomalacia and focal osteosclerosis.

Q. Enlist the salient clinicopathological features of osteoporosis.
Ans. Clinicopathological features of osteoporosis (osteopenia):
• Common clinical syndrome affecting multiple bones
• Characterized by quantitative reduction of bone tissue mass resulting in a fragile
skeleton associated with increased risk of fractures and consequent pain and deformity
• Common in elderly and postmenopausal women
• May be asymptomatic or may manifest with chronic backache; more extensive involvement
is associated with fractures, particularly of distal radius, femoral neck and vertebral bodies

Predisposing Factors
• Genetic factors (60–80%, variation in bone density genetically determined; associated
genes are RANKL, OPG and Receptor Activator of Nuclear Factor k B (RANK), which
are the key regulators of osteoclasts)
• Sex (more common in females)
• Ageing (decreased replicative and biosynthetic activity of osteoprogenitor cells and
osteoblasts with ageing results in senile osteoporosis)
• Reduced physical activity (decreases replicative and biosynthetic activity of osteopro-
genitor cells and osteoblasts)
• Starvation (decreased nutritional intake causes deficiencies)
• Intake of systemic steroids, anticonvulsants and heparin (interfere with calcium
metabolism)
• Deficiency of sex hormones (oestrogen in females and androgen in males), deficiency
of vitamin D and hyperparathyroidism.

Radiology

• Radiological evidence becomes apparent only after more than 30% of bone mass is lost.
• Levels of serum calcium, inorganic phosphorus and alkaline phosphatase are usually
within normal limits.

Pathology

• Osteoporotic trabeculae are thinned out with loss of their interconnections.
• Cortex thinned out by subperiosteal and endosteal resorption.
• Haversian system widened; sometimes so much that the cortex mimics cancellous bone.

Q. Enlist the salient clinicopathological features of hyperparathyroidism.

Ans. Hyperparathyroidism may be:
• Primary: Due to autonomous hyperplasia and a neoplastic growth (usually adenoma)
• Secondary: Caused by a prolonged state of hypocalcaemia

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