Molds as a cause of asthma and exacerbations

Molds are often found in patients with pre-existing asthma, when they can be the cause of worsening asthma and even death. However, they can also represent a risk factor for the development of asthma in a previously healthy person. The most allergenic molds causing respiratory diseases are: Aspergillus, Alternaria, Penicillium and Cladosporium with an emphasis on Aspergillus in patients with asthma. In order to be inhaled their spores must be ≤5 µm in size. Germination of inhaled mold spores in the lungs is related to Th2 and Th17 pathways, as well as activation of the innate immune system, but also could promote sensitization to allergens of other mushrooms, as well as allergy to pollens and dust mites. Sensitization rates in asthma patients range from 5-50% of patients. Molds can act as internal or external sources of respiratory allergens depending on the climatic conditions. The diagnosis of fungal allergy is complicated by the fact that patients with mold allergy are often polysensitized to pollen as well. Therefore, a good allergic anamnesis and clinical picture play a key role. Regarding diagnostic procedures, the most important are serum fungal-specific IgE or precipitins, total IgE, IgG against suspected fungus, peripheral blood eosinophils and fungal-specific skin prick tests. The role of antifungal therapy in severe asthma remains unclear. Further research is needed to better define the potential utility of antifungal drugs in patients with asthma and mold sensitization or allergy to identify drugs and populations of patients who would benefit from such treatment. There is also insufficient evidence for the safety and efficacy of allergen immunotherapy in mold-sensitive patients. About 70% of patients with severe eosinophilic asthma with sensitization or allergy to Aspergillus and Penicillium could benefit with Mepolizumab therapy. On the other side, measures to avoid mold still remain key factor in therapy.