Cutaneous Protothecosis:Unique Histopathological Finding with Crystal Violet Staining and the Therapeutic Effect of Itraconazole

Cutaneous protothecosis sometimes poses diagnostic and therapeutic problems. Isolation of the causative organism may not be successful and spores may be mistaken for other diseases unless the characteristic sporangia are detected in tissue sections. Because there are few cases, the optimal therapy is still being debated. Our purposes were to detect any characteristic findings of Prototheca wickerhamii under light microscopy in order to aid diagnosis and to determine which drugs were effective. On crystal violet staining we found characteristic bluish dots in Prototheca spores; these correspond to the amyloplasts or dense bodies found under electron microscopy. In vitro the isolated organisms were inhibited by itraconazole, amphotericin B, ketoconazole, and amorolfine and we were able to successfully treat three patients with itraconazole. Crystal violet staining can be helpful in diagnosing protothecosis, especially when the causative organism has not been isolated. The therapeutic effect of itraconazole was confirmed in vivo and in vitro.