Dr. Marinescu is a Senior Rheumatology Fellow, Albert Einstein College of Medicine, New York.

Diabetic muscular infarction, or DMI, was once considered an extremely rare complication of diabetes. Today, now that we can use non-invasive MRI imaging to detect DMI very easily — rather than using a muscle biopsy, the old way — we know that the condition is more common than previously thought, though still fairly rare. Because its symptoms can be easy to miss, DMI is often not noticed or treated as quickly as it should be. Anyone who has diabetes or who has a loved one with the disease should be aware of the possibility of developing DMI. If you suspect that you or a loved one might have DMI, then you should seek immediate medical attention.

What is DMI?
Diabetic muscular infarction causes a sore, painful area in a muscle, usually a thigh muscle; it is called diabetic because it is caused by circulation problems that are the result of long-term diabetes. Infarction is a medical condition in which tissue dies because its blood supply is cut off. DMI sometimes occurs in the calf muscles (19% of all cases). It is most common in people who have lived for years with type 1 diabetes (which typically is childhood diabetes and requires insulin) and who have poor glycemic control; that is, for whatever reason, they have not been able to keep their blood sugar levels under control. Women are more likely than men to get DMI. Most of the patients with DMI have diabetes-related damage to other organs as well, including the kidneys (71%), eyes (57%) and nerves (54.5%).

Because its symptoms can be easy to miss, DMI is often not noticed or treated as quickly as it should be.

DMI can come and go. It typically begins with muscle pain and swelling. After that, the pain partially subsides and a tender mass appears that can be felt through the skin. Of the muscles in the thigh, the quadriceps is the most commonly affected muscle. Both thighs are affected in 8% of cases. In a minority of cases, DMI causes fever and skin redness. There is only one known case of DMI in an arm muscle.

Perhaps because people who suffer from DMI often do not understand what it is, there is often a significant lag between the time people first have DMI symptoms and when they seek medical attention. According to one survey, the average delay is approximately 4 weeks. Treated with rest and pain killers, the symptoms gradually go away over time. DMI recurs in 48% of cases, about 9% involving the originally affected muscle and 39% involving another muscle.

Testing for DMI
Standard x-rays are rarely helpful in diagnosing DMI. The most valuable diagnostic tool is the MRI.

What Causes DMI?
We do not have a complete understanding of exactly what causes DMI or how the disease progresses. While arteriosclerosis, (hardening of the arteries), and diabetic microangiopathy, (damage to the small blood vessels caused by diabetes), are almost always present in those with DMI, it is thought that something else sets off the muscle infarction itself. One theory is that an initial blood vessel blockage produces muscle tissue damage, leading to an inflammatory response and an increase in blood flow to the area. This in turn leads to swelling. As the muscle swells in its closed compartment, it increases pressure on the small blood vessels and reduces blood flow further. This vicious cycle causes extensive muscle tissue death.

The thigh muscles may be particularly vulnerable because they, like the muscles of the heart, carry a heavy mechanical load as we walk or carry out other normal daily activities.

In most cases, an MRI test is all your doctor needs to diagnose DMI. A muscle biopsy can confirm the correct diagnosis, but is rarely necessary.

Treating DMI
Experts disagree on what is the best treatment of the diabetic muscle infarction (DMI). The current trend favors conservative management, (i.e., bed rest and pain killers), over medical treatment (i.e., anti-platelet drugs and steroids), and surgical therapy. Studies show that DMI sufferers who had either conservative or drug therapy had a significantly shorter recovery time and fewer recurrences of DMI than those who underwent surgery. There are also the usual postoperative complications from surgery to be considered, including infection and delayed wound healing. The experts also differ on whether or not physical therapy helps or hurts recovery from DMI.

In one study that compared surgery to conservative treatment,11 conservative therapy was the clear winner. Recovery time was 11.6, 8.5, and 18.6 weeks in the conservatively-, medically-, and surgically-treated patients, respectively. Recurrence rates were 35% (9 of 26) in the conservative group, 29% (2 of 7) in the medical group, and 71% (5 of 7) in the surgery group. The mortality rates were 4% (1 of 25) in the conservative group, 14% (1 of 7) in the medical group and 29% (2 of 7) in the surgery group.

While it may be more common than previously thought, diabetic muscular infarction is a rare complication of diabetes that causes pain, swelling, and a lump in the muscle.

The best way to diagnose DMI is with an MRI; a muscle biopsy is done only in unusual cases.

DMI tends to go away by itself or after rest, immobilization of the affected muscle or limb, and a course of pain-killers. In the minority of cases where this does not work, some doctors will prescribe anti-coagulant drugs, steroids or even surgery. The short-term prognosis of DMI is usually good — because the muscle infarction is treatable — but the overall prognosis for those who are prone to DMI is poor — because DMI usually occurs at the same time that diabetes is causing serious and, ultimately, life-threatening damage to other organs.