Glossitis

Glossitis is the inflammation of the tongue, a condition that can be acute or chronic, localized or diffuse, and may involve the mucosa, submucosa, and underlying musculature. The tongue is a highly vascular and mobile organ essential for prehension, mastication, swallowing, grooming, and thermoregulation in dogs and cats. Inflammation can arise from a variety of causes, including infectious agents, trauma, foreign bodies, chemical irritants, immune-mediated diseases, and neoplasia. Glossitis can be classified based on the predominant inflammatory cell type (e.g., lymphocytic, plasmacytic, eosinophilic, granulomatous) or by the underlying etiology. It may occur as a primary condition or secondary to systemic diseases such as uremia, feline calicivirus infection, or autoimmune disorders. The clinical significance ranges from mild discomfort to life-threatening anorexia, dehydration, and systemic infection. Prompt diagnosis and targeted therapy are essential to restore normal oral function and prevent complications such as aspiration pneumonia or sepsis.

The etiologies of glossitis are diverse and can be categorized as infectious, traumatic, toxic, immune-mediated, neoplastic, and idiopathic. Infectious causes include viral agents such as feline calicivirus (FCV), feline herpesvirus-1 (FHV-1), and canine papillomavirus; bacterial agents such as Pasteurella multocida, Streptococcus spp., Staphylococcus spp., and anaerobic organisms (e.g., Fusobacterium, Bacteroides) often secondary to trauma or foreign bodies; fungal agents such as Candida albicans (especially in immunocompromised patients) and rarely Aspergillus spp.; and parasitic agents such as Spirocerca lupi (in dogs) causing granulomatous lesions. Traumatic causes include foreign bodies (e.g., grass awns, sticks, bones, sewing needles), electrical cord burns, chemical burns (e.g., caustic substances, household cleaners), thermal burns (e.g., hot objects), and self-trauma from dental disease or malocclusion. Toxic causes include ingestion of irritant plants (e.g., Dieffenbachia, Philodendron) containing calcium oxalate crystals, and exposure to certain drugs (e.g., doxorubicin, cyclosporine) that can cause mucosal ulceration. Immune-mediated causes include eosinophilic granuloma complex (especially in cats), lymphocytic-plasmacytic stomatitis, and autoimmune diseases such as pemphigus vulgaris and systemic lupus erythematosus. Neoplastic causes include squamous cell carcinoma, melanoma, fibrosarcoma, and granular cell tumors. Metabolic causes include uremia (resulting in uremic stomatitis and glossitis) and diabetes mellitus (predisposing to candidiasis). Idiopathic glossitis is diagnosed when no specific cause is identified.

Glossitis can affect dogs and cats of any age, breed, or sex, but certain predispositions exist. In cats, eosinophilic granuloma complex (including eosinophilic glossitis) is more common in young to middle-aged cats, with no strong breed predilection, though some reports suggest a higher incidence in females. Feline calicivirus-associated glossitis is common in multi-cat environments, shelters, and catteries, particularly in kittens and unvaccinated cats. In dogs, traumatic glossitis is more common in working and hunting breeds due to increased exposure to foreign bodies and environmental hazards. Brachycephalic breeds (e.g., Bulldogs, Pugs) may be predisposed to glossitis due to dental overcrowding and periodontal disease. Immune-mediated glossitis may be more common in certain breeds, such as the Cavalier King Charles Spaniel for lymphocytic-plasmacytic stomatitis, though this primarily affects the oral mucosa rather than the tongue specifically. Geographic and seasonal variations exist for certain infectious causes, such as fungal infections in endemic areas (e.g., histoplasmosis in the Ohio River Valley). Overall, the incidence of glossitis is not well-documented, but it is a relatively common presentation in veterinary practice, often secondary to dental disease or trauma.

The pathophysiology of glossitis involves a complex interplay of tissue injury, inflammatory mediator release, and immune response. Initial injury to the tongue mucosa, whether from trauma, infection, or chemical irritation, disrupts the epithelial barrier, exposing underlying connective tissue and triggering an acute inflammatory response. This response is characterized by vasodilation, increased vascular permeability, and recruitment of neutrophils, macrophages, and lymphocytes to the site of injury. Pro-inflammatory cytokines such as tumor necrosis factor-alpha (TNF-α), interleukin-1 (IL-1), and interleukin-6 (IL-6) are released, promoting further inflammation and tissue damage. In infectious causes, pathogens directly invade the epithelium and submucosa, releasing toxins and enzymes that exacerbate tissue necrosis. For example, feline calicivirus replicates in oral epithelial cells, causing vesicle formation and ulceration. In immune-mediated conditions, an aberrant immune response targets self-antigens or dietary allergens, leading to chronic inflammation with infiltration of lymphocytes, plasma cells, and eosinophils. Eosinophilic granuloma complex involves degranulation of eosinophils, releasing cytotoxic proteins that cause tissue damage and collagen degeneration. Chronic inflammation can lead to fibrosis, scarring, and loss of lingual papillae, impairing tongue function. In severe cases, ulceration can become secondarily infected with anaerobic bacteria, leading to necrotizing glossitis and potential systemic spread via the rich vascular supply of the tongue. Additionally, pain and inflammation can cause anorexia, dehydration, and malnutrition, further compromising immune function and delaying healing.

Predisposing factors for glossitis include intrinsic and extrinsic elements. Intrinsic factors include age (young animals are more susceptible to viral infections; older animals may have dental disease and neoplasia), breed (brachycephalic breeds with dental overcrowding; certain breeds with immune-mediated disorders), and immune status (immunosuppression from FIV, FeLV, or chronic corticosteroid use increases susceptibility to fungal and viral infections). Metabolic diseases such as uremia and diabetes mellitus predispose to uremic glossitis and candidiasis, respectively. Extrinsic factors include poor oral hygiene, dental calculus and periodontal disease, which create a nidus for bacterial overgrowth and trauma. Dietary factors, such as ingestion of coarse or sharp food items, bones, or foreign bodies, can cause mechanical injury. Environmental exposure to toxic plants or chemicals increases the risk of chemical burns. Management factors, such as housing in crowded or unsanitary conditions, facilitate the spread of infectious agents. Concurrent oral diseases, such as stomatitis, gingivitis, or neoplasia, can also predispose to glossitis. Additionally, iatrogenic factors, such as radiation therapy to the head and neck or certain chemotherapeutic agents, can cause mucositis and glossitis.

Clinical signs of glossitis vary depending on the severity and underlying cause. Peracute and acute cases often present with excessive drooling (ptyalism), halitosis, reluctance to eat or drink (anorexia, dysphagia), pawing at the mouth, and vocalization. Physical examination may reveal a swollen, reddened, and painful tongue, with or without visible ulcers, vesicles, erosions, or foreign bodies. The tongue may be covered with a pseudomembrane or necrotic tissue in severe cases. Cats with eosinophilic glossitis may have raised, firm, linear or nodular lesions on the dorsal or lateral surface of the tongue. In chronic cases, signs may include weight loss, lethargy, and persistent oral discomfort. Systemic signs such as fever, depression, and dehydration may be present if secondary infection or sepsis occurs. In uremic glossitis, the tongue may appear pale with uremic ulcers, and other signs of renal failure (e.g., vomiting, azotemia) are present. In feline calicivirus infection, glossitis is often accompanied by oral ulcers on the hard palate, nasal discharge, and conjunctivitis. In severe necrotizing glossitis, the tongue may become dark, necrotic, and malodorous, with potential for systemic dissemination.

Differential diagnoses for glossitis include: 1) Stomatitis (generalized oral inflammation) – may involve the tongue but also affects other oral mucosa; key features include severe gingivitis, halitosis, and pain, often with lymphocytic-plasmacytic infiltrate on biopsy. 2) Oral neoplasia (e.g., squamous cell carcinoma, melanoma, fibrosarcoma) – typically presents as a mass or non-healing ulcer; biopsy is definitive. 3) Eosinophilic granuloma complex (in cats) – can affect the tongue, but also the lips, palate, and skin; histopathology shows eosinophilic infiltrate and collagen degeneration. 4) Uremic stomatitis – associated with chronic kidney disease; oral ulcers and uremic breath, with elevated BUN and creatinine. 5) Feline calicivirus infection – oral ulcers on the tongue and hard palate, often with upper respiratory signs; PCR or virus isolation from oral swabs. 6) Foreign body (e.g., grass awn, stick) – may cause localized swelling and draining tract; imaging or oral examination under anesthesia may reveal the object. 7) Chemical or thermal burns – history of exposure; lesions may be diffuse and necrotic. 8) Autoimmune diseases (e.g., pemphigus vulgaris) – vesiculobullous lesions on the tongue and other mucocutaneous junctions; biopsy with direct immunofluorescence. 9) Candidiasis – white, adherent plaques on the tongue; cytology or biopsy shows yeast and pseudohyphae. 10) Lingual abscess – localized swelling with purulent discharge; imaging and cytology. Definitive diagnosis relies on thorough history, physical examination, and diagnostic testing.

The diagnostic approach to glossitis should be systematic. Step 1: Obtain a thorough history, including onset, duration, progression, dietary habits, exposure to toxins or foreign bodies, vaccination status, and any systemic signs. Step 2: Perform a complete physical examination, with particular attention to the oral cavity. Sedation or general anesthesia may be required for a thorough oral examination, including inspection of the ventral tongue, sublingual area, and pharynx. Step 3: If a foreign body is suspected, perform oral radiography or advanced imaging (CT) to identify radiopaque objects; for radiolucent objects, oral endoscopy may be helpful. Step 4: Collect samples for cytology (impression smears, fine-needle aspirates) and biopsy (punch or excisional) of lesions for histopathology and culture (aerobic and anaerobic). Step 5: Perform baseline laboratory tests, including CBC, serum biochemistry, and urinalysis, to assess for systemic disease (e.g., uremia, diabetes). Step 6: If infectious etiology is suspected, perform specific tests: PCR for feline calicivirus or herpesvirus, fungal culture, or bacterial culture and sensitivity. Step 7: If immune-mediated disease is suspected, consider additional tests such as antinuclear antibody (ANA) titers, direct immunofluorescence on biopsy samples, and response to immunosuppressive therapy. Step 8: In cases of suspected eosinophilic granuloma complex, histopathology is diagnostic. Step 9: If neoplasia is suspected, staging with thoracic radiographs and lymph node aspiration is recommended. Step 10: Based on the results, establish a definitive diagnosis and initiate appropriate treatment.

Laboratory findings in glossitis are often non-specific but can provide clues to the underlying cause. Complete blood count (CBC) may reveal leukocytosis with a left shift in bacterial infections, eosinophilia in eosinophilic granuloma complex or parasitic infections, and lymphopenia in viral infections. Anemia may be present in chronic disease or blood loss from ulceration. Serum biochemistry may show elevated globulins in chronic inflammation or infection, hypoalbuminemia in protein-losing enteropathy or malnutrition, and elevated BUN and creatinine in uremic glossitis. Hyperglycemia may indicate diabetes mellitus, predisposing to candidiasis. Electrolyte imbalances (e.g., hypokalemia) may occur due to decreased food intake or vomiting. Urinalysis may reveal proteinuria, casts, or low urine specific gravity in renal disease. Blood gas analysis may show metabolic acidosis in severe systemic illness. Specific biomarkers such as C-reactive protein (CRP) may be elevated in inflammatory conditions. In suspected infectious causes, serology or PCR for feline calicivirus, feline herpesvirus, or fungal pathogens (e.g., Cryptococcus, Histoplasma) can be performed. In immune-mediated cases, ANA titers may be positive in systemic lupus erythematosus. Cytology of impression smears or aspirates may show inflammatory cells (neutrophils, macrophages, eosinophils), infectious organisms (yeast, bacteria), or neoplastic cells. Histopathology is the gold standard for definitive diagnosis, revealing the type and extent of inflammation, presence of infectious agents, or neoplastic infiltration.

Imaging plays a limited but sometimes crucial role in the diagnosis of glossitis. Oral radiography is useful to identify radiopaque foreign bodies (e.g., needles, bones) or dental disease that may contribute to glossitis. However, many foreign bodies (e.g., grass awns, wood) are radiolucent and may not be visible on radiographs. Ultrasonography can be used to evaluate the tongue for abscesses or foreign bodies, but it is operator-dependent and may require sedation. Computed tomography (CT) provides excellent detail of the tongue and surrounding structures, and is particularly useful for detecting foreign bodies, assessing the extent of neoplasia, or evaluating for osteomyelitis of the mandible. Magnetic resonance imaging (MRI) offers superior soft tissue contrast and is valuable for evaluating deep tongue lesions, abscesses, or neoplasms. Endoscopy (oral or pharyngeal) allows direct visualization of the tongue and can be used to retrieve foreign bodies or obtain biopsies. Fluoroscopy may be used to evaluate swallowing function if dysphagia is present. In cases of suspected systemic disease, thoracic radiographs may be indicated to rule out metastatic disease or fungal infection. Overall, imaging is most beneficial when a foreign body or neoplastic process is suspected, and the choice of modality depends on availability and the clinical scenario.

Cytology and histopathology are essential for definitive diagnosis of glossitis. Cytological evaluation of impression smears, scrapings, or fine-needle aspirates can reveal inflammatory cell types (neutrophils, macrophages, lymphocytes, plasma cells, eosinophils), infectious organisms (bacteria, yeast, fungal hyphae), and neoplastic cells. For example, the presence of numerous eosinophils and collagen degeneration is suggestive of eosinophilic granuloma complex. Candida organisms appear as budding yeast and pseudohyphae. Bacterial cultures and sensitivity testing should be performed on samples from deep lesions or abscesses. Histopathological examination of biopsy specimens provides a more comprehensive view of tissue architecture and inflammatory patterns. In acute glossitis, there is often ulceration, necrosis, and neutrophilic infiltration. Chronic glossitis may show lymphocytic-plasmacytic infiltration, fibrosis, and epithelial hyperplasia. Eosinophilic granuloma complex is characterized by eosinophilic infiltration, collagen degeneration, and sometimes flame figures. Viral infections may show intranuclear inclusion bodies (e.g., herpesvirus) or intracytoplasmic inclusion bodies (e.g., calicivirus). Neoplastic lesions have characteristic cellular features. Special stains, such as Gram stain for bacteria, Gomori methenamine silver (GMS) or Periodic acid-Schiff (PAS) for fungi, and immunohistochemistry for specific antigens, can aid in diagnosis. Biopsy should be performed on representative lesions, and multiple samples may be needed to avoid sampling error.

Treatment of glossitis depends on the underlying cause and severity. Emergency stabilization is the first priority: if the animal is dehydrated or anorexic, intravenous fluid therapy (e.g., lactated Ringer's solution at 40-60 ml/kg/day for maintenance plus deficits) and nutritional support (e.g., esophagostomy tube or nasogastric tube) may be necessary. Pain management is crucial; opioids such as buprenorphine (0.01-0.02 mg/kg IV/IM/SC q8-12h) or butorphanol (0.2-0.4 mg/kg IV/IM/SC q2-4h) are commonly used. Non-steroidal anti-inflammatory drugs (NSAIDs) may be used in dogs (e.g., carprofen 2.2 mg/kg PO q12h) but should be avoided in cats or in patients with renal or gastrointestinal disease. For infectious causes, appropriate antimicrobial therapy should be initiated based on culture and sensitivity results. Empirical therapy may include amoxicillin-clavulanate (12.5-25 mg/kg PO q12h) or clindamycin (5-10 mg/kg PO q12h) for anaerobic coverage. For fungal infections, fluconazole (5-10 mg/kg PO q12-24h) or itraconazole (5-10 mg/kg PO q24h) may be used. For viral infections, supportive care is the mainstay, but famciclovir (40-90 mg/kg PO q8h) may be used in cats with herpesvirus. For immune-mediated glossitis, immunosuppressive doses of corticosteroids (e.g., prednisolone 1-2 mg/kg PO q12h) are often used, with tapering over weeks to months. In cases of eosinophilic granuloma complex, a combination of corticosteroids and cyclosporine (5-10 mg/kg PO q24h) may be effective. Surgical intervention is indicated for foreign body removal, debridement of necrotic tissue, or excision of neoplastic masses. Supportive care includes oral hygiene (e.g., chlorhexidine rinses 0.12% twice daily), soft or liquid diets, and avoidance of irritants. In severe cases, feeding tubes may be required until the tongue heals. Regular monitoring and adjustment of therapy are essential.

The prognosis for glossitis varies widely depending on the underlying cause and the timeliness of treatment. Acute traumatic or infectious glossitis generally has a good to excellent prognosis if the inciting cause is removed and appropriate therapy is initiated promptly. Most animals recover within 1-2 weeks with supportive care. Viral glossitis, such as feline calicivirus, typically resolves within 1-2 weeks, but secondary bacterial infections can complicate recovery. Eosinophilic granuloma complex in cats often responds well to immunosuppressive therapy, but recurrence is common, and long-term management may be needed. Immune-mediated glossitis, such as lymphocytic-plasmacytic stomatitis, can be challenging to manage and may require lifelong immunosuppression; the prognosis is guarded to fair. Neoplastic glossitis carries a poor to grave prognosis, especially for malignant tumors like squamous cell carcinoma, with median survival times of 6-12 months even with aggressive treatment. Chronic glossitis can lead to fibrosis and permanent tongue dysfunction, affecting the animal's ability to eat and groom. Negative prognostic indicators include severe systemic signs, immunosuppression, delayed diagnosis, and the presence of neoplasia. Overall, early diagnosis and targeted treatment are associated with better outcomes.

Follow-up care for glossitis depends on the underlying cause and response to treatment. For acute cases, re-evaluation should occur within 7-14 days to assess healing and resolution of clinical signs. For chronic or immune-mediated cases, regular re-checks every 2-4 weeks initially, then every 1-3 months, are recommended to monitor response to therapy and adjust drug dosages. Serial laboratory tests, including CBC and serum biochemistry, may be needed to monitor for drug side effects (e.g., bone marrow suppression with immunosuppressive agents) and to assess systemic health. In cases of bacterial or fungal infection, repeat cultures may be indicated to ensure eradication. For neoplastic conditions, regular imaging (e.g., thoracic radiographs, CT) and lymph node evaluation are necessary to monitor for metastasis. Owners should be educated on oral hygiene, including regular tooth brushing and dental cleanings, to prevent recurrence. Dietary modifications, such as feeding soft or moistened food, may be necessary during the healing phase. If a feeding tube was placed, its removal should be based on the animal's ability to eat adequately. Long-term management may include maintenance immunosuppressive therapy for immune-mediated diseases, with gradual tapering to the lowest effective dose. Any recurrence of clinical signs should prompt immediate re-evaluation.

Pearls: 1) Always perform a thorough oral examination under anesthesia if glossitis is suspected, as the tongue's ventral surface and sublingual area are often overlooked. 2) Consider foreign bodies in any case of acute glossitis, especially in outdoor or hunting dogs; grass awns are a common cause. 3) In cats, eosinophilic granuloma complex is a common cause of glossitis; look for linear, raised lesions on the tongue. 4) Uremic glossitis is a classic sign of chronic kidney disease; always check renal parameters in older animals with oral ulcers. 5) Biopsy is essential for definitive diagnosis of chronic or non-healing glossitis; do not rely solely on cytology. 6) Pain management is critical; inadequate analgesia can lead to anorexia and delayed healing. Pitfalls: 1) Do not use NSAIDs in cats or in animals with suspected renal or gastrointestinal disease; this can exacerbate the condition. 2) Avoid using corticosteroids without a definitive diagnosis, as they can worsen infectious causes. 3) Do not overlook the possibility of systemic disease; glossitis may be a manifestation of a more serious condition. 4) Failure to culture and sensitivity test bacterial infections can lead to antimicrobial resistance. 5) Do not assume that all glossitis is idiopathic; a thorough diagnostic workup is essential. 6) In cases of suspected neoplasia, do not delay biopsy; early intervention improves prognosis.

Drug protocols for glossitis are tailored to the underlying cause. For pain management, opioids such as buprenorphine (0.01-0.02 mg/kg IV/IM/SC q8-12h) or butorphanol (0.2-0.4 mg/kg IV/IM/SC q2-4h) are commonly used. NSAIDs may be used in dogs without contraindications: carprofen (2.2 mg/kg PO q12h), meloxicam (0.1-0.2 mg/kg PO q24h), or robenacoxib (1-2 mg/kg PO q24h). For bacterial infections, amoxicillin-clavulanate (12.5-25 mg/kg PO q12h) or clindamycin (5-10 mg/kg PO q12h) are first-line choices. Metronidazole (10-15 mg/kg PO q12h) may be added for anaerobic coverage. For fungal infections, fluconazole (5-10 mg/kg PO q12-24h) or itraconazole (5-10 mg/kg PO q24h) are effective. For viral infections, famciclovir (40-90 mg/kg PO q8h) may be used in cats with herpesvirus. For immune-mediated glossitis, prednisolone (1-2 mg/kg PO q12h) is the mainstay, with tapering over 4-8 weeks. Cyclosporine (5-10 mg/kg PO q24h) may be used as a steroid-sparing agent. For eosinophilic granuloma complex, a combination of prednisolone (1-2 mg/kg PO q12h) and cyclosporine (5-10 mg/kg PO q24h) is often effective. In severe cases, a short course of injectable dexamethasone (0.1-0.2 mg/kg IV q24h) may be used. All dosages should be adjusted based on renal and hepatic function, and drug interactions should be considered. For example, concurrent use of NSAIDs and corticosteroids increases the risk of gastrointestinal ulceration and should be avoided. Monitoring for adverse effects, such as bone marrow suppression with cyclosporine or hepatotoxicity with itraconazole, is essential.

Evidence-based literature on glossitis in veterinary medicine is limited, but several studies and consensus guidelines provide guidance. A study by Southerden et al. (2017) evaluated the clinical features and outcomes of eosinophilic granuloma complex in cats, reporting that a combination of corticosteroids and cyclosporine was effective in most cases. Another study by Wray et al. (2019) investigated the prevalence of feline calicivirus in cats with oral ulcers, highlighting the importance of PCR testing for diagnosis. The ACVIM consensus statement on the diagnosis and management of chronic inflammatory oral diseases in dogs and cats (2020) recommends a stepwise approach, including biopsy and culture, for chronic glossitis. A retrospective study by Niemiec (2008) on oral foreign bodies in dogs found that grass awns were the most common, and early removal resulted in excellent outcomes. Regarding antimicrobial therapy, the ISCAID guidelines (2019) recommend culture and sensitivity testing for bacterial infections, with empirical therapy based on local resistance patterns. For pain management, the WSAVA guidelines (2016) emphasize multimodal analgesia, including opioids and NSAIDs, with caution in cats. Overall, the literature supports a thorough diagnostic workup and targeted therapy for glossitis, with a good prognosis for most non-neoplastic causes.