Observing pretibial myxedema in patients with Graves' disease using digital infrared thermal imaging and high-resolution ultrasonography: for better records, early detection, and further investigation.
Level 4 - case-series / case-control
Cross-sectional comparative diagnostic/observational study with healthy and disease controls
PubMed 21266550 · doi:10.1530/EJE-10-1095
What was done
Digital infrared thermal imaging (DITI) and high-resolution soft tissue sonography were evaluated as non-invasive tools to detect and record pretibial myxedema (PM) in Graves' disease (GD). The study evaluated DITI in 101 participants across four groups: 19 GD patients with PM, 22 GD patients with mild diffuse non-pitting leg edema, 46 GD patients with normal-appearing lower legs, and 14 normal volunteers. A subset of 61 participants (8 PM, 21 mild edema, 21 normal appearance GD, and 11 normal volunteers) also underwent soft tissue sonography.
What was found
Normal volunteers displayed lower leg temperatures that decreased gradually from proximal to distal areas. Focal low temperatures over PM lesions were detected by DITI in 100% (19/19) of overt PM patients, 90.9% of GD patients with mild edema, and 65.2% of GD patients with normal-appearing legs. Sonography in areas of low focal temperature and clinical PM showed increased skin thickness, hypoechoic substance deposition, and blurred dermis-subcutaneous boundaries. TSH receptor antibody levels correlated positively with skin thickness change (P = 0.046) and adjusted temperature difference between the defect center and surrounding skin (P = 0.033).
Why it matters
Combining DITI and high-resolution ultrasound provides an objective, non-invasive method for documenting PM lesions and identifying early subclinical localized tissue changes in patients with Graves' disease.
Limits
The total sample size was modest (n = 101 for DITI and n = 61 for sonography, with only 8 overt PM cases undergoing ultrasound). The cross-sectional design did not evaluate whether subclinical imaging abnormalities reliably progress to overt pretibial myxedema, and the study did not test specificity against non-thyroidal causes of lower-extremity edema.
Cited by
- supports Hypothyroidism causes myxedema, a proteinaceous edema visible in tissues under ultrasound.