Osteomalacia

Discussion

• is a type of metabolic bone disease in which the essential problem is a lack of available calcium or phosphorus (or both) for mineralization of newly formed osteoid;
• children w/ rickets & adults w/ osteomalacia present w/ similar findings;

etiology of rickets and osteomalacia

• • hyperthyroid induced osteopenia:
  • chronic use of anticonvulsant medication:
  • deficiency states:
    • vitamin-D deficiency: (strict vegetarians or an extremely low fat diet);
    • gastrointestinal and bilary causes;
  • renal osteodystrophy
  • fibrous dysplasia or neurofibroma:
    • osteomalacia & rickets are rare osteoendocrine or neuroendocrine manifestations of fibrous dysplastic or neurofibromatous dz;

anatomic changes in rickets and osteomalacia

• anatomical and pathological changes differ according to age of patient and the severity of the disorder;
• rickets affects the growing skeleton & thus affects both the epiphyseal plates as well as the bones of children;
• osseous changes in osteomalacia are similar to those in children but are much less evident because adult skeleton is metabolically less active;

Clinical Manifestations

• pts generally complain of easy fatigability, malaise, and bone pain;
• pain is diffuse and poorly localized and is accompanied by a general tenderness of bones;
• frx in an elderly individual that is thought to be the result of osteoporosis may be first sign of osteomalacia, & these patients must be evaluated carefully;
  • all symptomatic elderly patients should be screened for occult disease;
• bizarre complaints may give impression that patient has mental aberration;
• muscular weakness is often seen in severe cases;
• proximal muscle weakness may be evident & pt may have T-burg gait;

Radiographs

• Looser's zones:
  • osteoid seams are insufficiency types of stress frx which are commonly seen in patients with osteomalacia;
  • they are more common in adults than in children;
• patients may have findings of osteomalacia / renal osteodystrophy such as decreased mineralization, coarsened texture of the bones, "rugger-jersey" appearance of spine, and, occasionally, bowed long bones;
• most of these patients have chronic renal disease;

Histologic examination

biopsy

• biopsy is frequently necessary to provide diagnosis, which allows assessment of the number and thickness of osteoid seams per unit area;
• look for wide osteoid seams;
• there is less mineralized trabecular & cortical bone per unit volume of bone;
• tetracycline labeling helps confirm decreased mineralization of osteoid seams;

stress frx

• unmineralized areas (also called Looser's zones or pseudofractures) are occasionally seen roentgenographically;
• these zones are caused by rapid resorption & slow mineralization, are generally perpendicular to bone cortex;
• if stress frx occurs, it may be surrounded by a collar of callus;

osteoid seam

• osteoid seams in osteomalacia are wider than seam found in other diseases;
• diff dx: widened osteoid seams may be found in:
  • rickets;
  • osteomalacia;
  • hyperparathyroidism;
  • fibrous dysplasia;
  • bone-forming tumors;

Laboratory Aspects: Osteomalacia

• hypocalcemia
• hypophosphatemia:
  • phosphorus level is low or very low depending on type of osteomalacia, except in renal osteodystrophy;
  • renal osteodystrophy;
    • phosphorus level is invariably high & calcium level will be quite low;
• alk phos:
  • usually elevated in all forms of osteomalacia (except hypophosphatasia)

Reference

• Massive osteolysis.