This paper is an attempt to assess the usefulness of ultrasonography in the diagnosis of the enlargement of the tongue (macroglossia). The role of sonography in diagnosing local pathologies of the tongue, such as neoplasms, abscesses or granulomas, has been wellestablished for 20 years. Rarely is its usefulness considered with respect to diagnosing macroglossia with concomitant systemic diseases. The starting point of these considerations was the presented case of a 59-year-old patient with considerably enlarged tongue. The patient had difficulty speaking and ingesting meals. Moreover, he complained about swelling and pain in the carpal and proximal interphalangeal joints. Tongue ultrasound examination revealed blurred lingual structure with evident, irregular vascular pattern in the color Doppler. The obtained image helped to rule out local pathology of the tongue and directed our diagnostic considerations towards immunoglobulin-related diseases (deposition diseases). We believe that the presented ultrasound image of the tongue was helpful in the diagnostic process. Establishing the final, correct diagnosis was a particularly strenuous process. The suspicion of a deposition disease had been rejected during two previous stays in two hospitals. This was the consequence of a negative diagnostic test of staining tissue deposits with Congo red. An accurate diagnosis occurred to be a rare form of a deposition disease: lambda light chain disease with symptoms of amyloidosis. Such a diagnosis was based on a thorough hematological analysis. A high level of free lambda light chains in the serum was detected and the bone marrow biopsy showed 13% of plasma cells. The patient underwent chemotherapy.