Paradoxical Adipose Hyperplasia (PAH): CoolSculpting complication

Paradoxical Adipose Hyperplasia or PAH is a possible complication from cryolipolysis, commonly called fat freezing or by the brand name CoolSculpting, a modern non-invasive body contouring and targeted fat reduction technique that recently spiked interest because of this adverse event; Linda Evangelista, Canadian top model, filed a law suit for 50 Million USD against Zeltiq Aesthetics Inc., the company that makes the CoolScuplting machine now acquired by Allergan, because after undergoing six treatment sessions she was left “brutally disfigured” due to paradoxical adipose hyperplasia.

How does cryolipolysis work (CoolScuplting)?

CoolSculpting has been on the market since 2010. It works by cooling down the treatment area up to -15 °C (5 °F) with a special applicator that is left in place between 35 and 120 minutes. Only adipocytes, the fat cells, are affected by this low temperature and die while other types of tissues like skin, muscles, nerves, and blood vessels would need lower temperatures to cause them damage.

Cryolipolysis can reduce fat deposits in the treated area by up to 20% after a single session.

Normally as adults when we gain or lose weight the number of fat cells stays the same, but their volume increases or decreases. By selectively causing the death of fat cells and reducing their number in the treated area, the fat reduction is more permanent than what could be achieved with diet and exercise because we effectively impair the ability of that area to store lipids in the future.

paradoxical adipose hyperplasia or PAH as complication of CoolSculpting treatment

What is paradoxical adipose hyperplasia (PAH)?

Paradoxical adipose hyperplasia is a rare complication of cryolipolysis treatment, affecting less than 1% of subjects. It is characterized by the gradual development of a firm bulge in the treatment area 2 to 5 months after performing cryolipolysis.

The name of this adverse event means:

  • Paradoxical: unforeseen effect, that is the opposite of what you would actually expect
  • Adipose: related to fat tissue
  • Hyperplasia: an increase in the number of cells

PAH poses no health risk and is benign in nature, but it is cosmetically disfiguring and may lead to psychological stress as well.

Who is at risk for PAH?

In general, anyone undergoing even just a single treatment session of CoolSculpting may experience PAH. It seems to affect men three times more than women and those of Hispanic or Latino descent seem to be more likely to be affected by this complication. Larger and older applicators appear to have an increased occurrence of this adverse event while genetics may also play a role in the development of paradoxical adipose hyperplasia.

What are the symptoms of paradoxical adipose hyperplasia?

The main symptom of PAH is an increase in adipose tissue in the treatment area which is gradual and gets noticed around 2 to 3 months after performing cryolipolysis while continuing to grow for several weeks. This growth follows an initial decrease of subcutaneous fat in the region as you would normally expect from the treatment. The area affected is well demarcated with the same shape of the applicator used from the device and is often referred to as “stick of butter” effect. Unlike normal fat tissue, the one that forms due to paradoxical adipose hyperplasia feels firmer than its surrounding although not hard and may cause discomfort or slight pain on palpation.

What causes PAH?

Paradoxical adipose hyperplasia is not caused by weight gain and while there are a few hypotheses on the etiology, the causes are still unknown.

What areas can be affected by paradoxical adipose hyperplasia?

PAH has been reported in medical literature in all treatment areas including under the chin (submental region), thighs, “bra bulge”, flanks, abdomen, and upper arms. When patients experienced this complication and had more than one area treated, paradoxical adipose hyperplasia was reported in all sites.

What is the incidence of PAH?

Paradoxical adipose hyperplasia was originally reported to affect 1 in 20,000 patients according to CoolSculpting manufacturer, now increased to 1 in 3000 as per the safety information published on their website and with even higher incidence (1 every 256 treatments) according to other published research. Many patients are not aware of the condition which was diagnosed on follow-up appointments and thought it was due to normal fat deposits coming back; this suggests it’s an adverse event that gets misdiagnosed and/or is underreported but with more patient awareness more cases are being documented.

How long after CoolScuplting treatment can PAH develop?

PAH develops gradually over time and is generally noticeable 2 to 5 months after a treatment session.

How do you prevent PAH when doing CoolSculpting?

Newer models and new applicators of the CoolSculpting medical device seem to have a lower incidence in paradoxical adipose hyperplasia. This may be due to the fact that they are smaller, with a contoured design that requires less suction, have different cooling plates and use different treatment protocols (time and temperature).

One author suggests that the use of shock wave therapy (SWT) in combination with cryolipolysis, right after the treatment, may prevent paradoxical adipose hyperplasia from occurring. In his experience out of 2291 combined treatment performed over 4 years he had no occurrence of PAH. This finding requires further research to confirm it is beneficial.

Other than these unfortunately there’s no way of foreseeing this complication or preventing it from happening.

How to treat paradoxical adipose hyperplasia?

There are no reports of spontaneous resolution of PAH and the only solution seem to be the surgical one. The firmer nature of this fat tissue makes it harder to treat compared to normal adipose tissue. Further CoolScuplting treatment is unable to treat PAH. Diet and exercise don’t improve the appearance of this complication. It is recommended to wait 6 to 9 months after the initial cryolipolysis procedure before performing the revision surgery: this allows for the growth to stabilize, for the inflammatory phase to subside, and for the new adipose tissue to slightly soften making it easier to remove and making it less likely to require a second revision surgery. Power-assisted liposuction is generally reported in medical literature as the procedure of choice, with some cases requiring an abdominoplasty or a second surgical intervention because of recurrence or persistent bulge. Surgical excision may also be considered.

Ultrasound-assisted liposuction (like Vaser) and laser-assisted liposuction don’t seem to be able to solve the issue and may actually make the bulge even firmer, requiring further surgical intervention, although this may also be attributed to a premature surgery scheduled within 6 months from the CoolSculpting session.

What are the alternatives to cryolipolysis for targeted fat reduction?

There are several non-invasive targeted fat reduction alternatives to CoolSculpting, such as fat dissolving injections and multiple other medical devices although each and every medical and surgical procedure carries its own risks and possible complications. Always ask your treating physician for information so you can make an informed decision prior to being treated.

  • A Multicenter Evaluation of Paradoxical Adipose Hyperplasia Following Cryolipolysis for Fat Reduction and Body Contouring: A Review of 8658 Cycles in 2114 Patients.
    A Nikolis – Aesthetic Surgery Journal, Jul 2021
  • Treatment of Paradoxical Adipose Hyperplasia following Cryolipolysis: A Single-Center Experience.
    ME Kelly – Plastic and Reconstructive Surgery Journal, Jul 2018
  • Complications of Cryolipolysis: Paradoxical Adipose Hyperplasia (PAH) and Beyond.
    M Khan – Aesthetic Surgery Journal, Jul 2019
  • Paradoxical Adipose Hyperplasia after Cryolipolysis. A Report on Incidence and Common Factors Identified in 510 Patients.
    E Kelly – Plastic and Reconstructive Surgery Journal, Mar 2016
  • Shockwave Therapy for the Prevention of Paradoxical Adipose Hyperplasia After Cryolipolysis: Myth or Reality?
    A Michon – Aesthetic Surgery Journal, Aug 2021


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