Phoma betae
Summary
Neocamarosporium betae (previously known as Phoma betae) is a ubiquitous mold of the Order Pleosporales, found in soil and decaying plant materials worldwide. It is a well-known plant pathogen, causing mostly root and leaf damage. The main particles causing sensitization are airborne spores.
Hypersensitivity pneumonitis (HP), allergic rhinitis (seasonal allergy) and asthma are the main clinical presentations of P. betae allergy. This fungus is also able to cause opportunistic disease in humans. Cross reactivity with other molds, especially if taxonomically close, may occur.
Epidemiology
Worldwide distribution
Allergic conditions associated with P. betae have been described in many parts of the world, including North America, Hungary, and England. Allergic conditions attributed to P. betae sensitization ranged between 6-16% of patients with pre-existing allergies
Risk factors
Working in a museum may pose a risk factor due to higher exposure to molds and other microorganisms.
Route Of Exposure
Main
Inhalation of allergenic mold parts.
Clinical Relevance
The allergic conditions that may be caused by Phoma betae can vary. Acute eosinophilic pneumonia (AEP) is a disorder caused by diffuse lung damage with accumulation of eosinophils within alveolar and interstitial spaces, usually leading to rapid respiratory failure. It is thought that AEP may be an allergic reaction to specific antigens, which causes rapid accumulation of eosinophils. P. betae can be a cause of AEP as shown by a case report in which a 20-year-old man developed acute pneumonia symptoms of fever, tachycardia, crackles and wheezes at auscultation. Hypersensitivity testing was positive for P. betae IgE.
Asthma in children has been associated with environmental exposure to P. betae following Skin Prick Tests (SPTs).
Seasonal respiratory symptoms consistent with hay fever, which did not coincide with the release of grass pollens, were attributed to P. betae in 6.8% of patients included in a study carried out in London, England.
Occupational exposure and sensitization to P. betae has been reported. In a study testing for mold allergies in museum employees, 85% of patients reported at least one symptom of allergy (ranging from cough, dyspnea, wheezing, rhinitis, conjunctivitis and skin symptoms); 16% of patients had positive SPT to P. betae.
Diagnostics
Main methods
A Hirst spore trap can be used to sample air throughout a 24 hour period to collect fungal spores.
The presence of allergen-specific antibodies is determined by skin prick tests (SPTs) and serology for IgE.
Prevention And Therapy
Allergen immunotherapy
Immunotherapy is currently not recommended for patients allergic to molds, due to complexities of the allergens and patient co-allergies.
Prevention strategies
Avoidance is often not possible, as P. betae is a very common contaminant mold of decaying plant material.
Cross-Reactivity
Cross-reactivity has been demonstrated to other molds. 83% of patients with positive IgE reaction to P. betae were also positive to Alternaria alternata. In another study, the serum of 10 patients diagnosed with allergic fungal sinusitis (AFS) was used to determine whether IgE specific to other fungi (including P. betae) were present. All of the AFS patients showed a degree of cross reactivity to 6 other fungi. In a study carried out on 668 serum samples from patients which who had previously recorded at least one IgE positivity to fungal antigens, associations were observed between the patterns of IgE sensitization and fungal phylogenetic relationships. Using a panel of 17 fungal extracts including P. betae, some samples were only positive to one fungal species, whereas many were multi-sensitized. The results suggest that the associations are likely due to antigen cross-reactivity between fungal species, not uncommon in more closely related species.
References
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