# Resolution of Thyroid Acropachy in a Patient Treated With Teprotumumab: A Case Report and Review of Mechanisms

## TL;DR

A patient with thyroid acropachy showed significant improvement after treatment with teprotumumab, suggesting a new treatment option for this rare condition.

## Contribution

This is the first documented case of successful treatment of thyroid acropachy using teprotumumab.

## Key findings

- Teprotumumab led to significant clinical and radiological improvement in a patient with thyroid acropachy.
- The patient's musculoskeletal pain resolved, clubbing regressed, and periosteal bone formation diminished after treatment.

## Abstract

Graves' disease is an autoimmune thyroidopathy associated with hyperthyroidism and nonendocrine manifestations such as thyroid eye disease (TED), pretibial myxedema, and thyroid acropachy. Thyroid acropachy is an uncommon but debilitating condition, typically characterized by digital clubbing, soft tissue swelling, and periosteal new bone formation in the hands and feet. This condition often accompanies TED and dermopathy, but effective treatments remain elusive. The first documented case of thyroid acropachy successfully treated with teprotumumab, a monoclonal antibody targeting the insulin-like growth factor-1 receptor (IGF-1R), is reported here. A 49-year-old female with a history of Graves' disease developed severe musculoskeletal symptoms, including clubbing and periosteal new bone formation. Despite initial therapies with rituximab and intravenous immunoglobulin showing limited benefit, treatment with teprotumumab, primarily prescribed for TED, led to significant clinical and radiological improvement. After completing eight cycles of teprotumumab, the patient's musculoskeletal pain resolved, clubbing regressed, and radiologic findings of periosteal bone formation diminished. This case highlights the potential of teprotumumab as a novel therapeutic option for thyroid acropachy and suggests that IGF-1R plays a crucial role in its pathogenesis. While this report presents promising results, further studies are needed to confirm the efficacy of teprotumumab in treating thyroid acropachy and better understand its long-term effects on this rare condition.