Progressive muscular atrophy (PMA) is a rare adult-onset motor neuron disease. Although there’s no cure, treatments may slow down nerve damage and reduce symptoms.

Progressive muscular atrophy (PMA) is a rare type of motor neuron disease. Motor neuron diseases are a group of disorders characterized by progressive damage to your motor neurons — cells in your nervous system that allow you to perform functions such as speech, breathing, and movement.

PMA most commonly affects males and involves lower motor neuron damage. Lower motor neurons transmit signals between your spinal cord and muscles. Still, many people with PMA later develop damage to upper motor neurons, which originate in the brain.

Weakness in your arms and legs is a common symptom of PMA.

Keep reading to learn more about PMA’s symptoms, treatment, and risk factors.

PMA develops gradually. It may start with weakness in one part of your body, such as one hand. Over time, it usually spreads to other parts of your body.

Common symptoms of PMA include:

  • weakness in your hands, arms, core, or legs
  • clumsiness
  • difficulty breathing
  • fatigue
  • limp arms
  • muscle cramps or pain
  • twitching
  • unexplained weight loss

Some people with PMA report that cold temperatures make their symptoms worse.

At what age does progressive muscular atrophy usually appear?

PMA usually appears in late adulthood. Previous studies indicated that it may start at a younger age than other motor neuron diseases. However, a 2015 research review suggests that those studies may have included other conditions that resemble PMA and that the average age of onset may be closer to 63 years.

Unlike the similarly named spinal muscular atrophy, PMA does not occur in children.

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A doctor will ask you to describe your symptoms in detail. They’ll pose questions to learn more about your medical and family history and conduct a thorough physical examination.

The signs and symptoms of PMA can resemble those of several other conditions, including multiple sclerosis, amyotrophic lateral sclerosis (ALS), and brain and spinal cord tumors. Before diagnosing PMA, a doctor will recommend additional tests to rule out other conditions.

Doctors may also use other diagnostic tests, such as:

It can take months or even years to confirm a PMA diagnosis. During this time, your doctor will monitor and treat your symptoms and conduct regular tests.

There’s no standard treatment for PMA. Instead, your doctor will work with you to develop a treatment plan to help manage your symptoms and maintain your quality of life for as long as possible.

Common treatments include:

  • Medication: Riluzole is an ALS drug that may help slow down damage to motor neurons in PMA. Other medications can help relieve muscle cramps, pain, and twitching.
  • Nutritional counseling: The goal of nutritional counseling for PMA is to help you maintain a healthy weight and eat and drink safely.
  • Occupational therapy: An occupational therapist can provide suggestions to maximize your independence in daily life.
  • Physical therapy: Physical therapy involves exercises and stretches to improve your strength and flexibility.
  • Assistive devices: You might eventually need a cane, walker, or wheelchair to help you get around and avoid falls.

PMA is progressive, which means it will worsen over time. It often progresses very gradually and may affect only one part of your body for several years.

But the outlook varies a lot from one person to the next. It also depends on how severe your symptoms are at the time of diagnosis.

There’s not much recent research on life expectancy for people with PMA, but according to the United Kingdom–based Motor Neurone Disease Association, many people live at least 5 years from the onset of the condition. One 2009 study suggests that the median survival time for people with PMA is 1 year longer than for people with ALS.

Does PMA turn into ALS?

Though experts aren’t sure of the exact numbers, many people with PMA eventually develop upper motor neuron damage, which more resembles an ALS diagnosis. This has caused some experts to debate whether PMA is a less severe form of ALS rather than a separate condition.

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It’s not clear what causes PMA. It occurs sporadically, which means you don’t need to have a family history of PMA to develop it. However, it likely has a genetic component.

Possible risk factors for PMA include:

  • male sex
  • older age
  • previous exposure to environmental toxins
  • previous exposure to viruses
  • specific genetic mutations
  • previous nerve damage

PMA is a motor neuron disease that mostly affects adult males. It often starts with weakness in one hand and may progress to other areas of your body over time.

People with PMA report symptoms such as muscle weakness, pain, cramping, and twitching. Weight loss and fatigue are also common symptoms.

It can be difficult to get a diagnosis since PMA resembles several other conditions. If you think you might have PMA, it’s important to consult a doctor right away.