Does Allergy Break Bones? Osteoporosis and Its Connection to Allergy

Abstract

: Osteoporosis and allergic diseases are important causes of morbidity, and traditionally their coexistence has been attributed to causality, to independent processes, and they were considered unrelated. However, the increasing knowledge in the field of osteoimmunology and an increasing number of epidemiological and biological studies have provided support to a correlation between bone and allergy that share pathways, cells, cytokines and mediators. If the link between allergic pathology and bone alterations appears more subtle, there are conditions such as mastocytosis and hypereosinophilic or hyper-IgE syndromes characterized by the proliferation of cells or hyper-production of molecules that play a key role in allergies, in which this link is at least clinically more evident, and the diseases are accompanied by frank skeletal involvement, offering multiple speculation cues. The pathophysiological connection of allergy and osteoporosis is currently an intriguing area of research. The aim of this review is to summarize and bring together the current knowledge and pursue an opportunity to stimulate further investigation.

Keywords: IgE; allergy; asthma; bone; eczema; eosinophil; hypersensitivity; mastocyte; osteoporosis; skeletal health; translational immunology; urticaria.

Figure 1

The figure summarizes the relationship between allergic diseases and skeletal health.

Figure 2

The figure shows the complex network of relationships between allergy and bone. Mast cells that play a leading role in allergy but also in the regulation of bone metabolism through histamine, tryptase and other molecules. Osteopontin that regulate allergic inflammation and increase in osteoporosis. Periostin that regulate allergic inflammation and intervene in bone remodelling. IL-31 marker of allergic inflammation that increases in osteoporosis. IL-33 that influences both mast cells and eosinophils, modulate allergic inflammation and protect from inflammatory bone loss. Vitamin D, regulator of calcium/phosphate balance, recognized immunomodulatory agent, that inhibit secretion of mediators by mast cells, reduces eosinophils necrosis, release of peroxidase, production of IgE and increases expression of IL-10. Autophagy that regulate IL-33, in osteoimmunology limit inflammation and bone damage while in asthma contribute to airways inflammation, hyperresponsiveness and remodelling.