Osteomalacia
Encyclopedia
Osteomalacia is the softening of the bones caused by defective bone mineralization secondary to inadequate amounts of available phosphorus and calcium, or because of overactive resorption of calcium from the bone as a result of hyperparathyroidism (which causes hypercalcemia, in contrast to other etiologies). 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. It may show signs as diffuse body pains, muscle weakness, and fragility of the bones. The most common cause of the disease is a deficiency in vitamin D
, which is normally obtained from the diet and/or from sunlight exposure.
, 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 is derived from Greek: osteo- which means "bone", and malacia which means "softness". In the past tense of Brazilian narratives, the disease was also known as malacosteon and its Latin-derived equivalent, mollities ossium.
(lower back) region and thighs, spreading later to the arms and ribs. The pain is symmetrical, non-radiating and is 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
.
Due to demineralization bones become less rigid. Physical signs include deformities like triradiate pelvis and lordosis
. The patient has a typical "waddling" gait. However, those 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
. The major factor is an abnormally low vitamin D concentration in blood serum.
Major typical biochemical findings are:
Furthermore, a technetium
bone scan will show increased activity.
weekly of vitamin D for four to six weeks. Osteomalacia due to malabsorption may require treatment by injection or daily oral dosing of significant amounts of vitamin D.
Rickets
Rickets is a softening of bones in children due to deficiency or impaired metabolism of vitamin D, magnesium , phosphorus or calcium, potentially leading to fractures and deformity. Rickets is among the most frequent childhood diseases in many developing countries...
, and because of this, use of the term osteomalacia is often restricted to the milder, adult form of the disease. It may show signs as diffuse body pains, muscle weakness, and fragility of the bones. The most common cause of the disease is a deficiency in vitamin D
Vitamin D
Vitamin D is a group of fat-soluble secosteroids. In humans, vitamin D is unique both because it functions as a prohormone and because the body can synthesize it when sun exposure is adequate ....
, which is normally obtained from the diet and/or from sunlight exposure.
General characteristics
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 osteoporosisOsteoporosis
Osteoporosis is a disease of bones that leads to an increased risk of fracture. In osteoporosis the bone mineral density is reduced, bone microarchitecture is deteriorating, and the amount and variety of proteins in bone is altered...
, 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 is derived from Greek: osteo- which means "bone", and malacia which means "softness". In the past tense of Brazilian narratives, the disease was also known as malacosteon and its Latin-derived equivalent, mollities ossium.
Causes
The causes of adult osteomalacia are varied, but ultimately result in a vitamin D deficiency:- Insufficient nutritional quantities or faulty metabolism of vitamin DVitamin DVitamin D is a group of fat-soluble secosteroids. In humans, vitamin D is unique both because it functions as a prohormone and because the body can synthesize it when sun exposure is adequate ....
or phosphorusPhosphorusPhosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks... - Renal tubular acidosisRenal tubular acidosisRenal tubular acidosis is a medical condition that involves an accumulation of acid in the body due to a failure of the kidneys to appropriately acidify the urine. When blood is filtered by the kidney, the filtrate passes through the tubules of the nephron, allowing for exchange of salts, acid...
- MalnutritionMalnutritionMalnutrition is the condition that results from taking an unbalanced diet in which certain nutrients are lacking, in excess , or in the wrong proportions....
during pregnancyPregnancyPregnancy refers to the fertilization and development of one or more offspring, known as a fetus or embryo, in a woman's uterus. In a pregnancy, there can be multiple gestations, as in the case of twins or triplets... - MalabsorptionMalabsorptionMalabsorption is a state arising from abnormality in absorption of food nutrients across the gastrointestinal tract.Impairment can be of single or multiple nutrients depending on the abnormality...
syndrome - HypophosphatemiaHypophosphatemiaHypophosphatemia is an electrolyte disturbance in which there is an abnormally low level of phosphate in the blood. The condition has many causes, but is most commonly seen when malnourished patients are given large amounts of carbohydrates, which creates a high phosphorus demand by cells,...
- Chronic renal failureChronic renal failureChronic kidney disease , also known as chronic renal disease, is a progressive loss in renal function over a period of months or years. The symptoms of worsening kidney function are unspecific, and might include feeling generally unwell and experiencing a reduced appetite...
- Tumor-induced osteomalacia
- Long-term anticonvulsantAnticonvulsantThe anticonvulsants are a diverse group of pharmaceuticals used in the treatment of epileptic seizures. Anticonvulsants are also increasingly being used in the treatment of bipolar disorder, since many seem to act as mood stabilizers, and in the treatment of neuropathic pain. The goal of an...
therapy - Coeliac diseaseCoeliac diseaseCoeliac disease , is an autoimmune disorder of the small intestine that occurs in genetically predisposed people of all ages from middle infancy onward...
Signs and Symptoms
- Weak bones
- Bone painBone painBone pain is a debilitating form of pain emanating from the bone tissue. It occurs as a result of a wide range of diseases and/or physical conditions and may severely impair the quality of life for patients who suffer from it...
- Spinal bone pain
- Pelvic bone pain
- Leg bone pain
- Muscle weakness
- Hypocalcemia
- Compressed vertebrae
- Pelvic flattening
- Fractures
- Easy fracturing
- Bone softening
- Bending of bones
- Bone fractures
Clinical features
Osteomalacia in adults starts insidiously as aches and pains in the lumbarLumbar
In tetrapod anatomy, lumbar is an adjective that means of or pertaining to the abdominal segment of the torso, between the diaphragm and the sacrum ...
(lower back) region and thighs, spreading later to the arms and ribs. The pain is symmetrical, non-radiating and is 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
Squatting position
Squatting is a posture where the weight of the body is on the feet but the knees are bent either fully or partially . In contrast, sitting, involves taking the weight of the body, at least in part, on the buttocks against the ground or a horizontal object such as a chair seat...
.
Due to demineralization bones become less rigid. Physical signs include deformities like triradiate pelvis and lordosis
Lordosis
Lordosis is a medical term used to describe an inward curvature of a portion of the lumbar and cervical vertebral column. Two segments of the vertebral column, namely cervical and lumbar, are normally lordotic, that is, they are set in a curve that has its convexity anteriorly and concavity...
. The patient has a typical "waddling" gait. However, those 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
Biochemical findings
Biochemical features are similar to those of ricketsRickets
Rickets is a softening of bones in children due to deficiency or impaired metabolism of vitamin D, magnesium , phosphorus or calcium, potentially leading to fractures and deformity. Rickets is among the most frequent childhood diseases in many developing countries...
. The major factor is an abnormally low vitamin D concentration in blood serum.
Major typical biochemical findings are:
- The serum calcium is low
- Urinary calcium is low
- Serum phosphate is low except in cases of renal osteodystrophyRenal osteodystrophyRenal osteodystrophy or chronic kidney disease-mineral and bone disorder is a bone pathology, characterized by bone mineralization deficiency, that is a direct result of the electrolyte and endocrine derangements that accompany chronic kidney disease...
- Serum alkaline phosphatase is high
Furthermore, a technetium
Technetium
Technetium is the chemical element with atomic number 43 and symbol Tc. It is the lowest atomic number element without any stable isotopes; every form of it is radioactive. Nearly all technetium is produced synthetically and only minute amounts are found in nature...
bone scan will show increased activity.
Radiographic characteristics
Radiological appearances include:- PseudofracturePseudofracture- Structure :A band of bone material of decreased density may form alongside the surface of the bone. Thickening of the periosteum occurs. The formation of callouses in the affected area is also common. This gives the appearance of a false fracture. Typical sites of involvement are the axillary...
s, also called Looser’s zones. - Protrusio acetabuliProtrusio acetabuliProtrusio acetabuli is an uncommon defect of the acetabulum. The acetabulum is the socket that receives the femoral head to make the hip joint. The hip bone of the pelvic bone/girdle is composed of three bones, the ilium, the ischium and the pubis. The socket is too deep and may protrude into...
, a hip joint disorder
Treatment
Nutritional osteomalacia responds well to administration of 10,000 IUInternational unit
In pharmacology, the International Unit is a unit of measurement for the amount of a substance, based on biological activity or effect. It is abbreviated as IU, as UI , or as IE...
weekly of vitamin D for four to six weeks. Osteomalacia due to malabsorption may require treatment by injection or daily oral dosing of significant amounts of vitamin D.
See also
- OsteopetrosisOsteopetrosisOsteopetrosis, literally "stone bone", also known as marble bone disease and Albers-Schonberg disease is an extremely rare inherited disorder whereby the bones harden, becoming denser, in contrast to more prevalent conditions like osteoporosis, in which the bones become less dense and more brittle,...
, the opposite of osteomalacia