Tinea imbricata is a dermatologic disease caused by the fungus Trichophyton concentricum. It is of a chronic nature and proven to be endemic in regions of the Pacific where it is known by the name ''bakua".
Tinea imbricata (TI) is a mycosis affecting the outermost layer of the skin and hair. It is endemic in tropical parts such as the Pacific countries and Brazil due to the warm and humid climate which complements the requirements of life for the causative organism Trichophyton concentricum . Moreover, this infection is more common in people living in poverty and unhygienic conditions. The onset of TI is in the youth and has a recurrent nature that affects the patient despite treatment. Both genders are affected equally, and the percentage of infected residents in endemic regions is about 10 - 20% . Therefore it is beneficial to inquire about previous travels to these regions or contact with potential carriers of this infection.
The mycosis produces characteristic concentric, polycyclic, squamous patterns on the skin that overlap or imbricate, contributing to the characteristic name. It does not cause inflammation and has a tendency to develop a central clearing . Lesions of TI can present with or without erythema and/or bothersome pruritus. Sites most frequently affected are the torso and extremities, nevertheless, the infection can spread to any location of the body . Additionally, tinea imbricata is known to originate in the facial epidermis of children and successively spread to parts of the body previously described . Patients may have a family history of this infection, as it is presumed that a defective immunologic response to Trichophyton concentricum antigens is of genetic origin . Also, transmission of the fungi is rather effortless and involves physical contact with the infected and contact with surfaces containing the organism.
To establish a diagnosis of tinea imbricata, a clinical evaluation, and observation of the classical appearance due to this infection (described in the "Presentation'' section) is usually sufficient. Microbiological culture and other tests for objective confirmation are seldom necessary but can be informative in situations where there is doubt or when a specific genus of fungi is required to be identified .
Mycological investigations are good tools for identifying the causative agent of the infection. A culture has to be grown in a specific medium i.e. Sabouraud dextrose agar medium with the addition of chloramphenicol, as well as cycloheximide. Under microscopic examination, a characteristic morphological structure of Trichophyton concentricum can be seen. The structural differences include short hyphae with septae and a presence of chlamydospores .
Biopsies can be performed for a histopathological examination. A finding confirming a T. concentricum infection includes hyphae invasion into the stratum corneum layer of the skin .
Polymerase chain reaction (PCR) can be performed with amplification of the ITS1-ITS2 region .