Clinical study on Alternaria spores sensitization
A. C. Negrini*, D. Berra, P. Campi, B. Cinti, R. Corsico, V. Feliziani, M. T. Gallesio, G. Liccardi, A. Loreti, G. Lugo, F. Marcucci, G. Marcer, M. Minelli, G. Nardi, G. Piu, A. Passaleva, M. Pozzan, P. Puccinelli, F. Purello D''Ambrosio, A. Venuti and P. Zanon
Ospedale S. Martino. Genova. Italy. *Servizio di Allergologia.
Correspondence:
Arsenio Corrado Negrini
Via Angelo Orsini, 16/2
16146 Genova (Italy)
SUMMARY
Background: sensitization to fungi spores is often associated with sensitization to other allergens and so it is difficult to estabilish the exact cause of illness.
Objective: the aim of the study was to evaluate a group of patients monosensitized to Alternaria and to establish the prevalence, periodicity and clinical profile of this kind of sensitization.
Methods: 37 subjects who were monosensitized to Alternaria (prick-test positive), according to a previous epidemiological study were evaluated. Clinical symptoms and the period of their occurrence were taken into consideration as well as immunological parameters (RAST).
Results: 20 patients (over 50%) included in the study proved to be affected by asthma associated with other allergic symptoms and 22 patients (60%) presented perennial symptoms. The RAST carried out on 34 monosensitized subjects proved positive in 11 and negative in 23.
Conclusions: Alternaria sensitization is characterized by a perennial periodicity with severe respiratory symptoms (asthma) which occur primarily in children. Prick test is preferable to and more reliable than RAST as a diagnostic test.
Key words: Alternaria. Mold allergy. Skin prick test.
RESUMEN
Introducción: la sensibilización a esporas de hongos se asocia frecuentemente con la sensibilización a otros alergenos, con lo que es difícil establecer la causa exacta de la enfermedad.
Objetivo: la finalidad del estudio fue evaluar a grupos de pacientes monosensibilizados a Alternaria y establecer la prevalencia, periodicidad y perfil clínico de esta clase de sensibilización.
Métodos: se estudiaron 37 pacientes monosensibilizados a Alternaria (prick test positivo) seleccionados en un estudio epidemiológico previo. También se consideraron los síntomas clínicos y su frecuencia, así como algunos parámetros inmunológicos (RAST).
Resultado: 20 pacientes (por encima del 50%) padecían asma asociada con otros síntomas alérgicos y 22 pacientes (60%) presentaban síntomas perennes. El RAST llevado a cabo en 34 pacientes monosensibilizados, fue positivo en 11 y negativo en 23.
Conclusiones: la sensibilización a Alternaria se caracterizó por ser perenne, cursar con síntomas respiratorios graves (asma) y tener lugar principalmente en niños. Es preferible y más fiable como test diagnóstico el test cutáneo que el RAST.
Palabras clave: Alternaria. Alergia a hongos. Test cutáneos.
INTRODUCTION
Fungi spores may cause allergic sensitization and the onset of allergic symptoms (1). This kind of sensitization is frequently associated with sensitization to other allergens (pollens, dust mites, animal danders, etc.). For this reason it is difficult to recognize which allergen is responsible for the onset of symptoms; it would therefore be necessary to study a group of patients monosensitized to a single type of fungi spore. In Italy Alternaria tenuis is the most frequent fungi spore responsible for sensitization.
AIM OF THE STUDY
The aim of the study was to establish the prevalence, periodicity and clinical profile of subjects monosensitized to Alternaria.
MATERIALS AND METHODS
A previous multi-center study had been carried out in Italy (3) in 20 different allergy outpatient divisions on 2,942 patients affected by respiratory diseases suspected of being of an allergic nature.
The patients'' personal clinical history was collected and all of them underwent a prick test with the most common inhalant allergens including Cladosporium, Aspergillus fumigatus, Alternaria tenuis (ALK-Abellò). The Alternaria tenuis diagnostic extract was standardized in biological units at a concentration of 100 BU/mL (4). Alternaria specific serum IgE (RAST) were evaluated in patients who proved positive to the Alternaria extract used for prick test (5).
RESULTS
Out of the 2,942 subjects studied, 306 (10.4%) showed prick test positivity to Alternaria tenuis and 37 (12% of the patients positive to moulds, equal to 1.25% of the total number of patients), 17 males and 20 females, were monosensitized to this mould. The age of these patients ranged from 4 to 56 years (mean age 21 years) and most of them were younger than 20 (Fig. 1).
Figure 1.--Subjects mosensibilized to Alternaria by sex and agegroup.
A positive family history for allergies was present in 50% of the patients; 15 of them lived in a rural area while the other 22 came from an urban center. Allergic symptoms had been present for less than 1 year or of up to 20 years. Twenty patients (over 50%) had asthma, either alone or associated with other symptoms (conjunctivitis, rhinitis), while 15 subjects (about 40%) had rhino-conjunctivitis; atopic dermatitis was present in 2 cases (Fig. 2). Twenty-two patients (60%) suffered from perennial symptoms while one third of the patients had spring or autumn symptoms, regardless of the environment or the kind of symptoms they suffered from. Alternaria serum specific IgE (RAST), which were evaluated in 34 patients, were positive, to different degrees, in 11 cases and negative in 23.
Figure 2.--Type of symptoms in subjects monosensitized to Alternaria.
DISCUSSION
Allergic sensitization to moulds has been described in several studies (6), but has not yet been clearly defined. The most difficult aspects are: the exact etiologic definition, the precise quantification of fungi spores in both the outdoor and indoor environment and the unreliability of the diagnostic extracts (either for in vivo or in vitro tests) in that their antigen composition is still variable and most diagnostic extracts are not standardized. In the case of pollen sensitization, there is a correlation between a precise pollen period (7) and the occurrence of symptoms. When, however, mould sensitization is suspected, the methods for an accurate etiologic diagnosis are still empirical and in most cases rely on the patient''s observation. The fact that 37 patients with respiratory allergic symptoms had a positive skin prick test to Alternaria alone is significant. Nevertheless, in a third of these subjetcs only (11/34) Alternaria serum specific IgE (RAST) were detectable. This clinical study showed the same results for both sexes. Moreover, it is interesting to note that most patients were under 20 and the majority of them under 10. This may mean that sensitization to Alternaria mainly occurs during infancy, as has already been observed in the case of mite allergy (8), due to early contact with mould allergens in the environment. Another very important finding which emerged from the study was the kind of symptoms the patients presented: asthma, alone or associated with other respiratory symptoms such as rhinitis, was present in over 50% of the patients, which confirms the particular clinical severity of sensitization to Alternaria. Indeed, severe clinical features, sometimes lethal in children, have been reported (9). As far as the patients'' environment (rural or urban) is concerned, there were no particular differences or particular seasonal periods for the onset of symptoms. Indeed, symptoms occurred all year round in 60% of the patients, in autumn and winter in 16% and in spring only in another 16%. This shows that Alternaria may be present in the indoor environment throughout the year. It is well known that Alternaria can be present in the home on vegetables and rotten foods, plants and window frames, while in the outdoor environment its reproduction is periodical, occurring in summer and autumn. It is also possible that, in time, patients who become sensitized to Alternaria during the most intense air-dispersion season acquire and maintain a high hyper-reactivity of the target organs which can cause the onset of clinical symptoms even under the effect of aspecific factors ("priming" effect).
CONCLUSIONS
From this study on Alternaria monosensitized subjects it is possible to deduce that allergic sensitization to Alternaria is a clinical event characterized by:
respiratory symptoms, mainly asthmatic and sometimes severe
presence throughout the year
development in young people and children
no relation to outdoor environment exposure.
The diagnosis of this kind of sensitization is particularly difficult and relies on the patient''s clinical history and on prick test results. Indeed, the in vitro tests are often negative even in the presence of a positive skin prick test (10). This may occur both because it is difficult to standardize the Alternaria extract, as fungi colonies are difficult to grow and their allergenic content is often variable (11), and because it is difficult to extract and maintain the allergen intact. Further studies are still necessary in order to assess spores concentration in the patient''s indoor and outdorr environment, as well as the clinical relevance of symptoms.
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