Osteomalacia

Osteomalacia (rickets)
Classification and external resources
Specialty Endocrinology
ICD-10 M83
ICD-9-CM 268.2
DiseasesDB 9351
MedlinePlus 000376
eMedicine ped/2014 radio/610
Patient UK Osteomalacia
MeSH D010018

Osteomalacia is the softening of the bones caused by deactivated bone mineralization primarily due to inadequate levels of available phosphate and calcium, or because of resorption of calcium. Osteomalacia in children is known as rickets, and because of this, use of the term "osteomalacia" is often restricted to the milder, adult form of the disease. Signs and symptoms can include diffuse body pains, muscle weakness, and fragility of the bones.

The most common cause of osteomalacia is a deficiency of vitamin D, which is normally derived from sunlight exposure and, to a lesser extent, from the diet.[1] The most specific screening test for vitamin D deficiency in otherwise healthy individuals is a serum 25(OH)D level.[2] Less common causes of osteomalacia can include hereditary deficiencies of vitamin D or phosphate (which would typically be identified in childhood) or malignancy.

Measures to prevent and treat osteomalacia usually revolve around intake of vitamin D and calcium supplements. Vitamin D should always be administered in conjunction with calcium supplementation since most of the consequences of vitamin D deficiency are a result of impaired mineral ion homeostasis.[3]

Nursing home residents and the homebound elderly population are at particular risk for vitamin D deficiency, as these populations typically receive little sun exposure. In addition, both the efficiency of vitamin D synthesis in the skin and the absorption of vitamin D from the intestine decline with age, thus further increasing the risk in these populations. Other groups at risk include individuals with malabsorption secondary to gastrointestinal bypass surgery or celiac disease, and individuals who immigrate from warm climates to cold climates, especially women who wear traditional veils or dresses that prevent sun exposure.[4]

Signs and symptoms

Osteomalacia is a generalized bone condition in which there is inadequate mineralization of the bone. Many of the effects of the disease overlap with the more common osteoporosis, but the two diseases are significantly different. There are two main causes of osteomalacia: (1) insufficient calcium absorption from the intestine because of lack of dietary calcium or a deficiency of, or resistance to, the action of vitamin D; and (2) phosphate deficiency caused by increased renal losses.

Osteomalacia in adults starts insidiously as aches and pains in the lumbar (lower back) region and thighs before spreading to the arms and ribs. The pain is symmetrical, non-radiating and accompanied by sensitivity in the involved bones. Proximal muscles are weak, and there is difficulty in climbing up stairs and getting up from a squatting position.

As a result of demineralization, the bones become less rigid. Physical signs include deformities like triradiate pelvis[5] and lordosis. The patient has a typical "waddling" gait. However, these physical signs may derive from a previous osteomalacial state, since bones do not regain their original shape after they become deformed.

Pathologic fractures due to weight bearing may develop. Most of the time, the only alleged symptom is chronic fatigue, while bone aches are not spontaneous but only revealed by pressure or shocks.

It differs from renal osteodystrophy, where the latter shows hyperphosphatemia.

Causes

The causes of adult osteomalacia are varied, but ultimately result in a vitamin D deficiency:

Diagnosis

Biochemical findings

Biochemical features are similar to those of rickets. The major factor is an abnormally low vitamin D concentration in blood serum.

Major typical biochemical findings include:[9]

Furthermore, a technetium bone scan will show increased activity (also due to increased osteoblasts).

Comparison of bone pathology
Condition Calcium Phosphate Alkaline phosphatase Parathyroid hormone Comments
Osteopenia unaffected unaffected normal unaffected decreased bone mass
Osteopetrosis unaffected unaffected elevated unaffected thick dense bones also known as marble bone
Osteomalacia and rickets decreased decreased elevated elevated soft bones
Osteitis fibrosa cystica elevated decreased elevated elevated brown tumors
Paget's disease of bone unaffected unaffected variable (depending on stage of disease) unaffected abnormal bone architecture

Radiographic characteristics

Radiological appearances include:

Treatment

Nutritional osteomalacia responds well to administration of 10,000 IU weekly of vitamin D for four to six weeks. Osteomalacia due to malabsorption may require treatment by injection or daily oral dosing[10] of significant amounts of vitamin D.

Etymology

Osteomalacia is derived from Greek: osteo- which means "bone", and malacia which means "softness". In the past, the disease was also known as malacosteon and its Latin-derived equivalent, mollities ossium. Osteomalacia is associated with increase in osteoid maturation time.

References

  1. ↑ MedlinePlus Medical Encyclopedia: Osteomalacia
  2. ↑ Longo, Dan L.; et al. (2012). Harrison's principles of internal medicine. (18th ed.). New York: McGraw-Hill. ISBN 978-0-07174889-6.
  3. ↑ Longo, Dan L.; et al. (2012). Harrison's principles of internal medicine. (18th ed.). New York: McGraw-Hill. ISBN 978-0-07174889-6.
  4. ↑ Kennel, KA; Drake, MT; Hurley, DL (August 2010). "Vitamin D deficiency in adults: when to test and how to treat.". Mayo Clinic Proceedings 85 (8): 752–7; quiz 757–8. doi:10.4065/mcp.2010.0138. PMID 20675513.
  5. ↑ Chakravorty, N. K. (1980). "Triradiate deformity of the pelvis in Paget's disease of bone.". Postgraduate Medical Journal 56 (653): 213–5. doi:10.1136/pgmj.56.653.213. PMC 2425842. PMID 7393817.
  6. ↑ "Autoimmunity research foundation, Science behind Vitamin D". Retrieved 2011-07-19.
  7. ↑ Pack, Alison (2008). "Bone health in people with epilepsy: is it impaired and what are the risk factors". Seizure 17 (2): 181–6. doi:10.1016/j.seizure.2007.11.020. PMID 18187347.
  8. ↑ Albany, Costantine; Servetnyk, Zhanna (2009). "Disabling osteomalacia and myopathy as the only presenting features of celiac disease: a case report". Cases Journal 2 (1): 20. doi:10.1186/1757-1626-2-20. PMC 2626577. PMID 19128487.
  9. ↑ Holick, Michael F. (19 July 2007). "Vitamin D Deficiency". New England Journal of Medicine 357 (3): 266–281. doi:10.1056/NEJMra070553. PMID 17634462.
  10. ↑ Eisman, John A. (1988). "6 Osteomalacia". Baillière's Clinical Endocrinology and Metabolism 2: 125–55. doi:10.1016/S0950-351X(88)80011-9.

See also

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