Figure legends
Figure 1. Both first fingers at the first visit. (a) The frontal view. (b) The lateral view. The nail of the left first finger has a vertical white line, the nail fold is reddish and swollen and the fingertip is enlarged compared to the right first finger.
Figure 2. Radiographic findings of both first fingers at the first visit. (a) The right first finger on X-ray. (b) The left first finger on X-ray. No fracture or bone erosion is seen in the left first finger. The left first finger has more soft tissue swelling than the right first finger.
Figure 3. MRI findings of left fingers at the first visit. (a) The left fingers on the T1-weighted axial image, (b) the left fingers on the T2-weighted axial image, and (c) the left first finger on STIR sagittal image. MRI showed a tumor with low intensity on T1-weighted axial image and high intensity on T2-weighted axial image and the short-tau inversion recovery (STIR) sagittal image between the nail plate and the distal phalanx (red arrow). The left first fingernail and the tumor are not in contrast and the border is indistinct on the T1-weighted image. The left first fingernail is thick and high intensity, unlike the second through fifth fingernail on the T2-weighted image.
MRI: magnetic resonance image
STIR: short-tau inversion recovery
Figure 4. US sagittal scan of the left first finger at the first visit. (a) Greyscale, (b) Power Doppler (see also Supplementary Videos 1). The US revealed an oval and well-defined tumor between the nail plate and the distal phalanx. The tumor was pushing up the nail root. The interior of the tumor was plastic with abundant blood flow within the tumor.
US: ultrasound
Figure 5. The pus from the onychodermal band. A culture examination revealed S. aureus .
S. aureus: Staphylococcus aureus
Figure 6. Improvement of the left first finger over time. (a) The frontal view after 2 months. (b) The lateral view after 2 months. (c) The frontal view after 4 months. (b) The lateral view after 4 months. The left fingernail gradually grew back to normal, and it completely improved after 4 months.
Figure 7. MRI and US findings after 4 months. (a) The left first finger on STIR sagittal image, (b) the left first finger on US sagittal scan (see also Supplementary Videos 2). The subungual abscess had completely disappeared.
MRI: magnetic resonance image
US: ultrasound
STIR: short-tau inversion recovery