Tamale foot: deposit of acid mucopolysaccharides in the synovial sheaths of extensor tendons of the foot, resembling tendinitis, in a patient with juvenile ankylosing spondylitis.

We describe a clinical case of juvenile ankylosing spondylitis (AS) that developed "pseudo-chronic tendinitis" of the foot. A 20-year-old male patient had HLA-B27 positive juvenile AS since he was 13 years old. At the age of 19 he presented chronic pain in the dorsum of the left foot. Examination disclosed an increased volume of the tarsal dorsum, with rubbery consistency, with no evidence of venous or lymphatic insufficiency, godette, or inflammation in laboratory tests, giving the foot the appearance of a tamale. Synovectomy of the foot extensor tendon sheath was followed by relief of pain and swelling. Histopathological study showed a deposit of acid mucopolysaccharides (MPS) with no inflammatory cell infiltrate. Tamale foot in juvenile AS may develop as a consequence of acid MPS deposit with no evidence of synovial inflammation. The good response to synovectomy suggests this is the preferred treatment for tamale foot.