Usefulness of minor salivary gland biopsy in the diagnosis of IgG4-related disease: a case report.

Although considered essential for diagnosing IgG4-related disease (IgG4-RD), biopsy of target organs is often difficult to perform. Such was the case of a 56-year-old man admitted with general malaise and weight loss. Computed tomography revealed swelling of the submandibular gland, mild dilatation of the main pancreatic duct, renal involvement, periaortitis, and swelling of the lymph nodes in the abdominal cavity. Laboratory testing revealed elevated serum IgG4 level. These findings were suggestive of IgG4-RD; however, the patient refused consent for biopsy of the target organs for a definitive diagnosis for the invasiveness. Therefore, we tried to perform a biopsy from minor salivary gland, which revealed no sign of clinical abnormality because the biopsy is not an invasive diagnostic procedure. As a result, the biopsy revealed significant IgG4-positive plasma cell infiltration, allowing for definitive IgG4-RD diagnosis. Administration of oral prednisolone (30 mg/day) effectively improved all symptoms. These findings indicate that minor salivary gland biopsy is an effective means of IgG4-RD diagnosis in patients for whom biopsy of target organs is difficult even if there were no sign of clinical abnormality in appearance.