Acute Sialadenitis: Post Covid-19 vaccination

A 46 years old woman presented with painful bilateral preauricular swelling more evident on right side and increasing for last week, post COVID-19 vaccination. On physical examination, there was a firm, indurated, tender non-fluctuant swelling at level of parotid glands. No associated overlying skin changes and no associated systemic complaints.

MRI face and neck was requested on ENT referral which depicted bilateral symmetrical enlarged parotid and left submandibular glands (Figure 1) which showed homogenous postcontrast enhancement and overlying subcutaneous oedema (Figure 2). No ductal dilation or obstructive sialolith was visualised. The left submandibular gland also showed similar enlargement and homogenous postcontrast enhancement (Figure 2). On Diffusion-weighted imaging, bilateral parotid glands show diffusion restriction with low values on corresponding ADC map (Figure 3). There was associated reactive cervical lymphadenopathy and left masseter muscle oedema.

Ultrasonography revealed enlarged bilateral parotid gland and left submandibular glands, which appear hypoechoic and show increased vascularity (Figure 4).

Acute sialadenitis refers to acute inflammation of the salivary glands. It can be caused by viral or bacterial infection, inflammatory condition (sarcoidosis) or any immune-mediated process (Sjogren syndrome) [1]. Sudden neck swelling is also a potential complication of the COVID-19 virus [2].
It has been found in animal models infected with SARS-CoV-2 virus where direct tropism for epithelial cells on the salivary gland through ACE-2 receptors was found [3]. The presence of SARS-CoV-2 in saliva with associated xerostomia suggests virus invasion into the salivary gland [4].
In our case, acute sialadenitis was seen after COVID-19 vaccination highlighting post-vaccine-associated acute sialadenitis in this pandemic. The patient received the first dose of her scheduled vaccine which contains the whole virion–inactivated SARS-CoV-2 antigen.
The swelling of the parotid gland usually begins posteriorly and then moves downward and forward with pushing the earlobe upward and outward. The swelling develops rapidly with the involvement of the submandibular gland.
In literature, acute parotitis after MMR vaccination was reported. Post-COVID vaccination acute sialadenitis is not reported, however acute sialadenitis is considered as an early atypical manifestation of COVID-19 virus [1]. In our case, diagnosis is established by imaging, FNAC and laboratory tests.
On MRI imaging of acute parotitis, the salivary gland appears enlarged and are homogenously enhancing with T1 isointense and T2 hyperintense signal. The gland shows areas of diffusion restriction with low values on the ADC map. No duct dilation or calculi were seen. On ultrasonography, salivary glands appear enlarged, hypoechoic and hyperaemic.
FNAC was performed in our case which was showing cellular and numerous epithelioid cells granuloma 
in reactive lymphoid background.
Laboratory tests included RT-PCR testing done for SARS-CoV-2 virus which was negative, C-reactive protein of 0.48mg/dl, TLC count of 6.8x103/L, d-dimer value of 0.42 and serum amylase of 143 U/L, amylase levels were elevated which confers clinical diagnosis of acute parotitis [5].
In consideration of clinical presentation, imaging findings and laboratory tests, acute sialadenitis involving bilateral parotid glands and left submandibular gland, post COVID-19 vaccination was considered as a diagnosis, ruling out other differential diagnoses in this pandemic.