12 Achilles Tendon and Heel Appearance Changes Linked to Metabolic Disorders

10. Amyloidosis and Tendon Infiltration

Amyloidosis, a group of disorders characterized by the abnormal deposition of misfolded proteins, can significantly affect the Achilles tendon and heel region, creating distinctive changes that reflect the underlying metabolic dysfunction. Primary amyloidosis (AL type) and secondary amyloidosis associated with chronic inflammatory conditions both show predilection for tendon involvement, with the Achilles tendon being one of the most commonly affected sites. The deposition of amyloid fibrils within the tendon structure creates characteristic changes in both the mechanical properties and appearance of the tissue, with affected tendons showing progressive thickening and loss of normal elasticity. The clinical appearance of amyloid-infiltrated Achilles tendons is distinctive, with patients developing firm, non-tender swelling that has a characteristic "woody" consistency quite different from the soft, fluctuant swelling seen in inflammatory conditions or the rope-like thickening of diabetic tendons. The tendon may appear enlarged along its entire length, and in advanced cases, the normal anatomical landmarks become obscured by the diffuse infiltration. Imaging studies reveal characteristic features including loss of the normal fibrillar pattern, increased tendon thickness with maintained echogenicity, and the absence of increased vascularity that would suggest inflammatory tendinopathy. Patients with hereditary amyloidosis, particularly those with transthyretin mutations, may show bilateral Achilles tendon involvement as an early manifestation of systemic disease, making recognition of these changes crucial for early diagnosis and treatment. The metabolic implications of amyloidosis extend beyond the local tendon effects, as patients often develop cardiac involvement, renal dysfunction, and neuropathy that require comprehensive management and monitoring.