The most important class of aeroallergenic fungi is Deuteromycetes which includes Alternaria, Cladosporium, Penicillium, Aspergillus and Phoma spp.;¹ many of these fungi can induce hypersensitivity pneumonitis (HP).² Types of HP caused by Penicillium spp. are cheese worker's (P. casei, P. roqueforti), humidifier lung (P. casei), woodman's (Penicillium spp.) and cork worker's diseases (suberosis, P. frequentans).^3-8

Penicilliosis, a systemic fungal infection caused by the thermal dimorphic pathogenic Penicillium marneffei, commonly has cutaneous manifestations (~75%)⁹ and is uniformly fatal in immunosuppressed patients (HIV, cancer and transplantation)¹⁰ if not treated expeditiously and appropriately.^9-11 Invasive infection can on occasion be due to other Penicillium spp.¹² Monoclonal antibody-based antigen detection assays are very promising for diagnosis,^13,14 as is direct detection in fine needle aspirates,¹⁵ all of which are more rapid than culture. The methods of choice at present involve DNA probes¹⁶ and PCR.¹⁷

Although EIA detects IgG antibodies and ID demonstrates precipitins to antigens of P. roqueforti and P. casei in serum and bronchoalveolar lavage fluid of individuals with cheese worker's and humidifier lung diseases,^6-8 the presence of antibodies is not diagnostic of HP, because these antibodies can be present in serum due to the ubiquitous nature of Penicillium spp. in the environment.¹⁸ IFA titers ¡Ý1:160 for P. marneffei-specific IgG in documented P. marneffei cases versus titers ¡Ü1:40 in other persistent-fever patients and healthy controls were reported; however, the test was evaluated in an area of low endemicity.¹⁹ Major IgE-reactive 64 kDa and 68 kDa antigens of P. notatum identified by IB are found at comparable frequencies in atopic patients and blood donors.²⁰ The presence of IgE antibodies to P. chrysogenum increases with age of asthmatic patients.²¹

Corneal (P. citrinum, P. expansum) and systemic (P. chrysogenum, P. spinulosum) hyalohyphomycosis and mycosis due to P. marneffei are diagnosed by isolation, culture and histopathology.^22-27 A completely automated method for the direct identification of pure Penicillium species solely by means of digital image analysis of colonies as seen after growth on a standard medium is described.²⁸ Using this digital image, precise and objective information can be extracted from the surface of the fungal colony including color distribution, colony dimensions and texture measurements. Multiplex PCRs for identification of yeasts and fungi are promising but do not yet include Penicillium spp.²⁹ Such multiplex assays will ultimately be very valuable for diagnosis of infections in immunocompromised patients³⁰ and in ocular infections.³¹

In the preparation of standardized diagnostic reagents, it is imperative to define the allergens of these ubiquitous fungi; results from studies on P. oxalicum suggest that the 34 kDa major immunoglobulin E-reacting component is a serine protease;³² whereas, the peroxisomal membrane protein (Pen c 3) is the important allergen component of P. citrinum.³³