Subcutaneous Rhytidhysteron Infection: A Case Report from South India with Literature Review

Abstract

Rhytidhysteron is a saprophytic dematiaceous fungus which rarely infects humans. Though virtually all individuals are exposed, very few develop the disease. Only seven human cases are reported till date. The present case is the second case from South India.A 40-year-old immunocompetent female agricultural worker, presented with a swelling on the dorsum of the right hand. Fine needle aspiration cytology (FNAC) of the swelling revealed short, thick, branched septate fungal hyphae. The isolate was moderately slow growing; grayish white colonies were observed on Sabouraud’s Dextrose Agar (SDA) slant. On further incubation, the colonies turned floccose, greyish black and the black pigment was observed on the reverse. Microscopy of lactophenol cotton blue tease mount showed thick, brown septate hyphae without any fruiting bodies. Molecular typing confirmed the isolates as Rhytidhysteron rufulum.Identification of all clinical isolates of nonsporulating fungi to genus level is necessary to identify rare fungi infecting humans.

Two new species of Gloniopsis (Hysteriales, Ascomycota) from clinical specimens: Morphological and molecular characterisation

“…However, morphological characterisation was not possible since the isolate remained sterile, highlighting growth only at 28°C and 37°C . Since then, more clinical cases mainly from India have been reported in patients with subcutaneous phaeohyphomycosis, and all of them caused by Rhytidhysteron rufulum identified only by ITS sequence analysis and without morphological descriptions …”

“…12 Since then, more clinical cases mainly from India have been reported in patients with subcutaneous phaeohyphomycosis, and all of them caused by Rhytidhysteron rufulum identified only by ITS sequence analysis and without morphological descriptions. [13][14][15][16] The present work provides two more isolates from clinical samples in the USA. Based on the morphological characterisation and molecular data, a new classification is given, amending the identification of Indian strains and proposing two novel species.…”

“…The clinical laboratory identification of these fungi was mainly based on DNA sequence of the internal transcribed spacer region (ITS1‐5.8S‐ITS2). As the isolates remained sterile in the culture media, morphological comparisons were not performed …”

“…As the isolates remained sterile in the culture media, morphological comparisons were not performed. [12][13][14][15][16] The present work revises the taxonomy of three isolates recovered from clinical specimens related with those in the order Hysteriales by combined phenotypic and molecular data. A multilocus analysis was performed using three molecular markers: the D1-D2 fragment of the 28S nuclear ribosomal RNA (nrRNA) (LSU), the internal transcribed spacer region (ITS) and a fragment of the translation elongation factor 1-alpha (tef1) gene.…”

Phaeohyphomycosis caused by Rhytidhysteron rufulum

“…Rhytidhysteron rufulum is a dematiaceous fungus that causes disease in plants, most commonly citrus and mangroves . Rare human infections are described, with previous cases exclusively in India . We report a case of phaeohyphomycosis caused by R. rufulum in a renal transplant patient in Tennessee, USA.…”