A 45-year-old woman from rural India presents with diffuse bone pain, proximal muscle weakness, and waddling gait. Lab shows: Ca 7.2 mg/dL, Phosphate 2.0 mg/dL, ALP 580 U/L, PTH elevated, 25-OH Vitamin D <10 ng/mL. X-ray shows Looser's zones (pseudofractures) at the medial femoral neck. Looser's zones are pathognomonic of:
- A Osteoporosis
- B Primary hyperparathyroidism
- C Paget's disease
- D Osteomalacia ✓
Explanation
Looser's zones (Umbauzonen) are bands of decreased density perpendicular to the cortex at sites of stress — representing unmineralized osteoid seams that have been replaced by fibrous tissue and new bone formation. They are pathognomonic of osteomalacia (and its rickets equivalent in children). Common sites: medial femoral neck, pubic rami, ribs, lateral scapulae. The biochemical profile of low calcium, low phosphate, elevated ALP (active osteoblasts), high PTH (secondary hyperparathyroidism), and low vitamin D confirms nutritional osteomalacia. Subperiosteal resorption of the radial border of middle phalanx is pathognomonic of hyperparathyroidism.
Reference: Maheshwari Essential Orthopaedics, 6th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.