Median rhomboid glossitis (MRG) refers to a well-demarcated, largely symmetric lesion of the dorsum of the tongue. This lesion corresponds to an area of papillary atrophy, although most patients remain asymptomatic. The etiology of this rather common condition remains essentially unknown. In general, treatment is not required. In determined cases, patients may benefit from an antifungal therapy.
MRG is a common condition and it has been estimated that up 1% of the population show some degree of central papillary atrophy . Men are affected about three times as often as women.
MRG appears as a well-demarcated, roughly rhomboid, erythematous and thus bright red lesion directly anterior to the vallate papillae . Commonly, it seems patchy as the rhomboid area still includes papilla-carrying spots that bear an off-white color. Its surface is smooth or lobulated, and rarely bears erosions . It may be slightly elevated above the surrounding tongue surface. While an MRG lesion is most commonly located in the midline of the dorsum of the tongue, paramedian occurrences have also been described . Usually, patients don't claim any other symptoms. In few cases only, they describe pruritus or pain in the affected area.
There may be a similar lesion in the opposing area of the palate. Such an anomaly is sometimes referred to as "kissing lesion". It may imply an infectious pathogenesis of MRG in an immunodeficient patient. Accordingly, diagnostic measures should be taken to assess their immune system. Diabetes mellitus should be considered in this context, but this variant of MRG is more commonly associated with an HIV infection and an acquired immunodeficiency syndrome .
MRG is usually diagnosed clinically. However, it may not always be feasible to distinguish an uncomplicated MRG from aphthous stomatitis, granuloma, precancerous erythroplakia or neoplasms like hemangioma, squamous cell carcinoma or granular cell tumor . In order to do so, a biopsy and subsequent analysis of the tissue sample is required. During a microscopic examination, the absence of papillae can be confirmed. Also, epithelial anomalies ranging from atrophic to hyperplastic changes are most commonly revealed . Atypical nuclei and numerous mitotic figures are not characteristic of MRG and may indicate a neoplasm, though. In underlying layers of tissue, infiltrating inflammatory cells may be visible. Immunohistochemical stains may be applied to further evaluate the cells' characteristics if deemed necessary.
Additionally, characteristic spores and yeast buds forming pseudohyphae can be recognized microscopically and reveal the presence of Candida spp. If doubts remain as to the presence of yeasts, samples can be subjected to fungal stains. Fungal cultures are rarely required, but may provide interesting epidemiological data. In general, MRG has been associated with chronic Candida infections: A recent microbiological study found Candida albicans to account for the majority of cases, while Candida kefyr, tropicalis, krusei and glabrata have also been isolated . However, one out of ten MRG patients tested negative for Candida spp. Non-Candida pathogens have occasionally been implicated in the development of MRG and may serve as an explanation in this regards .
As has been implied in the previous paragraph, if a kissing lesion is present or additional symptoms hint at a dysfunction of the immune system, this suspicion should be followed up.