Tophaceous Gout of the Extensor Mechanism of the Knee.

Abstract

A 51-year-old male presented at our department with a slightly painful soft tissue lump at the superior pole of the patella and limited range of joint motion. MRI of the left knee confirmed a soft tissue mass within the distal quadriceps extending into the superior aspect of the patella. The mass was hypointense on T1-weighted images (WI) (Fig. A, arrows) and slightly heterogeneous hyperintense on fat saturated intermediate-WI (Fig. B, arrows). A bone infarct was seen in the distal femur (Fig. A and B, arrowhead). After administration of gadolinium contrast heterogeneous enhancement was seen. Gradient-echo sequences did not reveal blooming artifact. Additionally Cone Beam CT showed the soft tissue mass as being slightly hyperdense to the surrounding soft tissue (Fig. C, arrow). Partially sclerotic delineated osteolysis was seen at the patella (Fig. C, arrowhead). Based on the clinical presentation and imaging findings, tophaceous gout was suspected. After repeated anamnesis, the patient admitted alcohol overconsumption for many years and having previous gout attacks at the feet. Because of the aggressive nature of the process, a biopsy was performed in order to exclude a malignant tumor. The biopsy specimen showed the presence of monosodium urate (MSU) crystals, in keeping with tophaceous gout. The patient was reassured, was provided with appropriate dietary advice and nonsteroidal anti-inflammatory drugs.