Osteomalacia

Generality

Osteomalacia is a metabolic disease affecting the bones, to which it removes minerals making them more susceptible to pain, malformations and fractures. We are therefore talking about a demineralizing metabolic osteopathy, characterized by the presence of non-calcified osteoid tissue in excess of the norm.

Osteomalacia should not be confused with osteoporosis, in which there is a reduction in the amount of bone matrix, moreover normally mineralized; in the osteomalacia, instead, the opposite condition occurs: the bone microarchitecture maintains a normal volume, but its mineral content is insufficient.

Causes

Osteomalacia is typical of adults, whereas when the mineralization defect affects the growing skeleton (children) one speaks more correctly about rickets. The causes of these diseases are to be found in alterations of the metabolism of vitamin D, calcium and phosphorus. At one time, the primary cause of rickets and osteomalacia was to be found in the vitamin D food shortage; today, thanks to the improvement of socio-economic conditions, dietary deficiencies have become rare (vegetarians are somewhat more at risk, even if adequate sun exposure can easily bridge this deficit).

Beyond insufficient dietary intake, specific deficiencies of vitamin D may develop due to poor or no sun exposure, or insufficient renal or hepatic activity (chronic liver disease, chronic renal failure). Moreover, being a fat-soluble vitamin, the intestinal absorption of vitamin D is compromised by all the conditions in which there is steatorrhea, or an excessive presence of fats in the feces, a sign of insufficient absorption of the same (eg celiac disease, pancreatic insufficiency, diverticulosis, Crohn's disease, gastric resection and small intestine),

Among the most represented minerals in the bone, a prominent role is covered by calcium and phosphorus, which when joined in hydroxyapatite crystals give the bones the characteristic hardness, well known to all. In the article dedicated to the metabolism of calcium, we have seen how the balance of the mineral in the body, as well as that of phosphorus, depends essentially on the activity of some organs, first of all the intestine, the kidney, the skin and the parathyroid glands. Vitamin D, on the other hand, increases the absorption of these minerals in the intestine and reduces urinary excretion,

Osteomalacia can therefore arise due to an altered availability of vitamin D, calcium or phosphorus, also due to the prolonged intake of drugs that alter the metabolism, such as anticonvulsants (phenytoin, carbamazepine, phenobarbital, primidone), some drugs against HIV, and aluminum hydroxide antacids.

Diagnosis

In the blood of a patient suffering from osteomalacia it is possible to find low levels of calcium and / or phosphorus, associated with markers of enhanced osteoblastic activity, such as the increase in alkaline phosphatase and osteocalcin (we briefly recall how the osteoblasts are the cells assigned to construction of the bone matrix). It may also be useful to carry out specific tests, such as the dosage of serum transaminases, azotemia and creatinine clearance, to assess the health of the liver and kidney in the face of suspicion of liver or kidney disease. In case of suspected celiac disease or malabsorption disease, the sorbitol breath test or the dosing of specific blood antibodies may be useful, while the diagnosis of hepatic failure involves the determination of trypsin, fats or elastase in the faeces.

The diagnosis can be confirmed by radiographic investigations, where - in the presence of osteomalacia - the typical pseudo-fractures of Looser-Milkmann are highlighted.

Symptoms

In the onset stages of the disease, the patient generally does not complain of any symptoms, while laboratory investigations can highlight the risk of osteomalacia from the earliest stages. When the disease progresses the affected individual may complain of bone and muscle pain; the symptomatology is often described as a dull pain in the bones, which generally affects the lower part of the spine, the pelvis, the hips, the legs or the ribs. Bone pain is typically exacerbated by slight pressure on the bones and movements. Often, in the radiographic findings there is a thin line of fracture in the areas where the pain is most intense. Furthermore, musculoskeletal pain can be accompanied by a reduction in muscle tone and strength, with uncertain and hesitant gait, and poor gait resistance. As anticipated, the risk of undergoing bone micro-fractures, also spontaneous, increases, especially in the aforementioned areas.

Treatment and care

If osteomalacia has arisen due to reduced sun exposure and / or insufficient dietary intake of vitamin D, the correction of plasma levels of this vitamin through specific dietary supplements is the best therapeutic option. Generally, people with osteomalacia take vitamin D supplements (ergocalciferol) orally, for a period ranging from a few weeks to several months; only in some cases, for example when the absorption of vitamin D at the intestinal level is compromised, or for reasons of practicality, is administered by intravenous injection. The dosage and duration of treatment must be carefully calibrated based on the patient's clinical, biochemical and radiological changes, but also on the basis of the drugs taken or particular concomitant conditions (high-dose vitamin D is for example contraindicated in the presence of kidney stones, hypercalcemia, hypercalciuria, primitive hyperparathyroidism or therapy with drugs such as digoxin and thiazide diuretics). Periodic checks on calcemia can turn off any poisonings caused by overdose of vitamin D in the bud, indicated by symptoms such as gastro-intestinal disorders, weight loss, irritability, low-grade fever, dry skin with scaling, vascular and especially kidney calcifications.

Alongside the specific integration of vitamin D, if the levels of phosphorus and calcium in the blood are particularly low, it is also possible to replenish these minerals. Finally, if osteomalacia were the consequence of other diseases, such as those in the liver or kidney, treating the underlying pathology that generates vitamin dysmetabolism can help improve the signs and symptoms of osteomalacia. Furthermore, in these cases it is essential to administer the deficient forms of active vitamin D (calcifediol in case of hepatic insufficiency, calcitriol in case of renal insufficiency). Finally, in the presence of an exocrine insufficiency of the pancreas associated with osteomalacia it is necessary to intervene with an adequate replacement therapy based on porcine pancreatic extracts (pancreatin, creon, pancrease).

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