Skeletal muscle pseudohypertrophy in primary amyloidosis

Area of Science:

• Neurology
• Oncology
• Pathology

Background:

• Amyloidosis is a rare disease caused by the buildup of abnormal proteins (amyloid) in organs.
• Light chain multiple myeloma is a cancer of plasma cells that can produce abnormal proteins.

Observation:

• A 38-year-old male presented with macroglossia (enlarged tongue) and skeletal muscle enlargement accompanied by weakness.
• Diagnostic workup revealed amyloidosis and light chain multiple myeloma, with free lambda light chains detected in serum and urine.

Findings:

• Skeletal muscle biopsies showed significant amyloid infiltration within blood vessel walls and connective tissue, alongside amorphous material.
• Muscle fibers, especially type II, exhibited diminished size, indicating muscle atrophy.
• Amyloid and amorphous deposits were also observed in skin samples.

Implications:

• This case illustrates an uncommon but distinct pattern of neuromuscular apparatus involvement in nonfamilial primary amyloidosis.
• The findings underscore the importance of considering amyloidosis in patients with unexplained macroglossia and neuromuscular symptoms.
• Further research into the specific mechanisms of amyloid deposition in the neuromuscular system is warranted.