Osteomalacia in Adults: A Practical Insight for Clinicians

Abstract

The term osteomalacia (OM) refers to a series of processes characterized by altered mineralization of the skeleton, which can be caused by various disorders of mineral metabolism. OM can be genetically determined or occur due to acquired disorders, among which the nutritional origin is particularly relevant, due to its wide epidemiological extension and its nature as a preventable disease. Among the hereditary diseases associated with OM, the most relevant is X-linked hypophosphatemia (XLH), which manifests in childhood, although its consequences persist into adulthood where it can acquire specific clinical characteristics, and, although rare, there are XLH cases that reach the third or fourth decade of life without a diagnosis. Some forms of OM present very subtle initial manifestations which cause both considerable diagnosis and treatment delay. On occasions, the presence of osteopenia and fragility fractures leads to an erroneous diagnosis of osteoporosis, which may imply the prescription of antiresorptive drugs (i.e., bisphosphonates or denosumab) with catastrophic consequences for OM bone. On the other hand, some radiological features of OM can be confused with those of axial spondyloarthritis and lead to erroneous diagnoses. The current prevalence of OM is not known and is very likely that its incidence is much higher than previously thought. Moreover, OM explains part of the therapeutic failures that occur in patients diagnosed with other bone diseases. Therefore, it is essential that clinicians who treat adult skeletal diseases take into account the considerations provided in this practical review when focusing on the diagnosis and treatment of their patients with bone diseases.

Keywords: FGF23; osteomalacia; phosphate; rickets; vitamin D.

Figure 1

The typical scintigraphic pattern suggestive of metabolic bone disease can be seen on the left and right part of the image: increased uptake of the radiotracer in periarticular areas, skull, mandible, osteochondral junctions of the ribs, sternum, and focal increased uptake in the femur and tibia suggest Looser–Milkman zones. Conventional radiography (central part of the figure) shows a Looser–Milkman zone on the medial aspect of the middle third of the right femur (arrow).

Figure 2

Multiple bone-insufficiency fractures in a patient with osteomalacia. Left upper part: fracture of the right hip (with surgical osteosynthesis) and pubic rami. Right side: multiple vertebral fractures. The lower-left picture shows a scintigraphic image consistent with fractures of the ilio and ischiopubic rami.

Figure 3

Diagnostic algorithm for hypophosphatemia.