Tinea capitis in south Wales--observations in change of causative fungi

We report an observed change in the causative organisms in 45 consecutive cases of tinea capitis seen in the Cardiff area over the last 9 years. Direct microscopy using potassium hydroxide was positive in all but one case, but this was subsequently positive on culture. This retrospective analysis shows that more cases are being seen in our department, and that a higher proportion of cases are due to Trichophyton violaceum whereas previously we would have expected the majority of cases to be due to Microsporum canis. We believe that the change in causative organism that we have identified has important practical and diagnostic implications. Endothrix fungi such as T. violaceum do not fluoresce under Wood's lamp unlike ectothrix fungi such as M. canis, and therefore failure to perform adequate mycological examination of specimens could result in missed diagnoses. We are not aware of this change having been reported from other UK centres. The finding indicates a need for further prospective epidemiological studies to confirm this apparent trend.