Juvenile primary Sjögren's syndrome (pSS) is rare. Although recurrent parotitis is reported to be the most common symptom of juvenile pSS, the clinical symptoms and features of the syndrome are not well understood and are poorly defined. Here we report a rare case of juvenile pSS in a patient with plunging ranula. The patient had no symptoms other than swelling of the oral floor and had no symptoms of parotitis. Magnetic resonance imaging (MRI) revealed the diagnosis of plunging ranula. In addition, the findings of the bilateral parotid glands on MRI and subsequent ultrasonography (US) strongly suggested SS. On the basis of these imaging findings and laboratory data, a pediatric rheumatologist confirmed the diagnosis of juvenile pSS. The ranula may be one clinical sign of SS. However, this association remains generally unknown. Hypothesizing that SS might cause ranula development, we retrospectively investigated cases of patients with ranula who underwent MRI at our hospital. We found that many of these patients (> 20%) had characteristic findings strongly suggestive of SS. This result suggests that SS-induced changes in the sublingual glands are one cause of ranula formation. We think that ranula is a sign of early-stage SS. Therefore, patients with ranulae, whether adults or children, should undergo careful assessment of not only the sublingual glands but also the parotid and submandibular glands with MRI and/or US to investigate possible SS. This assessment may lead to early detection of SS.
Keywords: Juvenile Sjögren’s syndrome; MR sialography; Magnetic resonance imaging; Ranula; Ultrasonography.