Treatment of Sebaceous Hyperplasia With a Novel 1,720-nm Laser

extended slightly beyond the lesion perimeter. Many of the lesions resolved almost completely after a single treatment, and no additional treatment was required. The data are presented in Table 2. Representative preoperative and postoperative photographs are noted in Figure 3. Overall, there was a notable reduction in color, diameter, and height of the lesions. Crusts were noted by all patients and resolved within 10 days. The one biopsy showed damage to the sebaceous glands that extended about 800 µm deep to the surface. The very deep portion of the lesion (800 µm to 2 mm below the surface) was unaffected (Figure 4).

Sakamoto et al examined 1,720-nm sebaceous gland heating based on Monte Carlo modeling and ex vivo experiments with a free electron laser using an ≈8 mm spot.⁸ Their data suggested a damage threshold fluence of about 67 J/cm² for a 50°C temperature rise based on 100 to 1,000 ms of heating. They also found about a 1.6 times differential between sebaceous gland heating and normal skin at selected fluences. Our clinical results are in line with their preliminary ex vivo results.

However, there are differences in the studies. In their work, a large spot was used, and normal-sized sebaceous glands were treated. In our case, only hyperplastic glands were treated. In these lesions, the glands almost abut the overlying skin surface.

Also, we targeted the lesion with a very small spot vs a larger spot. We did show selectivity, however, as normal adjacent skin was unaffected by a range of fluences used in the study. However, only small increases in dwell time and therefore fluence resulted in changes in normal skin. Whereas sebaceous hyperplasia lesions showed coagulation at 50 ms and 3.8 W, normal skin showed graying only at about 100 ms. The size of an average sebaceous hyperplasia lesion (about 1-2 mm) has a thermal relaxation time of about (assuming a spherical geometry) 1 second. Therefore, almost complete thermal confinement would be expected during the pulse.

The clinical end points with 1,720-nm irradiation differed from typical clinical end points with other modalities. For example, with the hyfrecator (probably the most common tool used in sebaceous hyperplasia treatment), a slight graying at the surface is noted. With the PDL, purpura is a typical end point, and with the 532-nm laser, we observe "whitening" as a common end point. In the later 2 modalities, presumably we are targeting the Hgb (hemoglobin) that courses through a typical sebaceous hyperplasia lesion, and indeed those vascular-type sebaceous hyperplasia lesions respond well to Hgb-specific lasers. Photodynamic therapy using aminolevulinic acid relies on sufficient protoporphyrin IX production and adequate light doses to photochemically/ photothermally alter the gland.

The advantage of sebum-selective approaches is a high likelihood of deeper heating of the gland. Most present methods only heat the most superficial portions of the gland, resulting in typical incomplete removal and rapid recurrence. Various physicians have tried to address this challenge. For example, Bader and Scarborough used the hyfrecator with a 1-second application of an epilating needle to heat up lobules without recurrences.⁴ Aghassi et al examined the role of PDL in sebaceous hyperplasia and found specific damage to the blood vessels.¹.Our fiber delivery system and small spot allowed for precise placement of the beam and, together with the intrinsic selectivity of 1,720 nm, achieved almost complete clinical destruction of the lesions without depressions or scarring. By exploiting the primary differentiating feature of the sebaceous gland vs normal skin, we achieved complete heating of the