What are other Names for this Condition? (Also known as/Synonyms)

• MCL (Mast Cell Leukemia)

What is Mast Cell Leukemia? (Definition/Background Information)

• Mastocytosis is a rare disorder that results from often abnormal and excessive numbers of mast cells in the skin and, rarely, in the organs. When the skin is affected, it is known as cutaneous mastocytosis; when the skin and other organs are affected, it is known as systemic mastocytosis
• Mast cells, which reside in the connective tissue, store chemicals important to initializing the inflammatory and allergic responses. Once activated, mast cells release chemicals including heparin, histamine, and serotonin that stimulate the body’s inflammatory response
• Mast Cell Leukemia (MCL) is reportedly a rare form of aggressive systemic mastocytosis (ASM), predominantly involving the bone marrow. In general, leukemia may be described as a form of blood cancer that develops from increased white blood cells in the body. However, MCL shares several overlapping features with systemic mastocytosis. The prognosis of MCL is extremely poor since it is a highly aggressive malignancy that does not respond well to treatment
• The tests and procedures to diagnose Mast Cell Leukemia may include general physical examinations, blood tests, imaging studies, skin and bone marrow biopsies, and genetic testing to detect KIT gene mutations. Presently, there are no standard treatment options for mastocytosis. Generally, management of the symptoms and controlling the inflammatory response is needed; this may involve anti-histamine treatment, chemotherapy, and bone marrow transplant

Who gets Mast Cell Leukemia? (Age and Sex Distribution)

• Mast Cell Leukemia is a very rare form of systemic mastocytosis
• Most cases are diagnosed in adults (median age of 52 years). Children are also known to develop the condition but to a much lesser extent
• Both males and females are susceptible to the condition; a slight female preference is noted (female-male ratio is 3:2)
• Worldwide, it can affect all racial and ethnic groups

What are the Risk Factors for Mast Cell Leukemia? (Predisposing Factors)

• A majority of Mast Cell Leukemia cases are observed in middle-aged and elderly adults
• A positive family history is rarely observed in mastocytosis; and, no other specific risk factors have been identified

However, in general, the following are believed to increase one’s susceptibility to mastocytosis:

• Smoking
• Exposure to radiation and industrial chemicals
• Chemotherapy
• In rare cases, viral infections

There are also a host of factors that may trigger histamine release further aggravating the skin signs and symptoms in mastocytosis. Some of these include:

• Medications such as opioid painkillers, non-steroidal anti-inflammatory drugs (NSAIDs), vitamin supplements, antibiotics, anticholinergics, etc.
• Venom injection from snake bites and bee stings
• Emotional stress
• Lack of sleep
• Hot or cold weather, and temperature changes
• Certain viral and bacterial infections
• Iatrogenic factors such as application of local anesthetic, vaccines, administration of contrast media, and even certain invasive procedures

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Mast Cell Leukemia? (Etiology)

The cause of formation of Mast Cell Leukemia is mostly due to mutations in the KIT gene. In some cases, it is caused by unknown factors.

• In a vast majority of cases, the condition occurs sporadically
• Occasionally, when mastocytosis is inherited, an autosomal dominant pattern of inheritance is noted

It is reported by medical experts that MCL can arise secondary to aggressive systemic mastocytosis or occur de novo (sporadically).

What are the Signs and Symptoms of Mast Cell Leukemia?

The signs and symptoms of Mast Cell Leukemia (MCL) may vary from one individual to another. It may be mild or severe. Involvement of the skin, bone, liver, spleen, and peritoneum, along-with bone marrow, is often noted.

The signs and symptoms of MCL may include:

• Abdominal pain
• Difficulty breathing
• Rapid heart rate (tachycardia)
• Low blood pressure (hypotension)
• Headache
• Anemia
• Diarrhea
• Ulcers in the gastrointestinal tract (affecting the stomach and small intestine)
• Bone and joint pain
• Muscle pain (myalgia)
• Blisters and hives (urticaria)
• Severe itching (pruritus)
• Flushed face and body
• Bone marrow dysplasia
• Swollen lymph nodes (lymphadenopathy)
• Enlarged liver and spleen (hepatosplenomegaly)
• Fatigue
• Weight loss due to malabsorption
• Neuropsychiatric symptoms

The presence of triggers, such as certain medications, sunlight, or medical procedures, may cause a flare up (inflammatory response) of the signs and symptoms.

How is Mast Cell Leukemia Diagnosed?

The following are some tests that may be used in the diagnosis of Mast Cell Leukemia:

• Physical exam to detect skin abnormalities and comprehensive medical history evaluation
• Blood smear to detect:
  • Increased numbers of mast cells
  • Abnormally-shaped mast cells
  • Reduced numbers of red blood cells (anemia)
  • Reduced numbers of platelets (thrombocytopenia)
• Blood tests to detect:
  • Elevated total tryptase levels which can indicate mast cell elevation in systemic disease
  • Elevated lactate dehydrogenase which is a prognostic aid in systemic disease
  • Elevated alkaline phosphatase levels which can indicate bone involvement in systemic disease
• Radiographic tests to detect bone deficiencies
• Bone marrow biopsy to detect increased cell numbers (hypercellularity) - this forms an important diagnostic procedure in diagnosing MCL
• Skin biopsy to detect:
  • Clusters of mast cells
  • Abnormally-shaped mast cells
• Genetic tests to detect a KIT mutation, if necessary

In order to diagnose systemic mastocytosis, one major and one minor, or three minor criteria, from the following list, must be satisfied:

• Major criterion: Dense infiltrates of more than 15 mast cells in multiple areas, such as in the bone marrow or an extracutaneous organ
• Minor criteria:
  • Aberrant phenotype on the mast cells (pos. for CD2 and/or CD25)
  • Aberrant mast cell morphology (spindle-shaped)
  • Finding of mutation in KIT(D816V)
  • Serum tryptase is over 20 ng/ml

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Mast Cell Leukemia?

Mast Cell Leukemia may result in significant complications that may include:

• Emotional stress
• Uncontrollable inflammatory and allergic reactions; severe reactions may result in anaphylaxis that can be life-threatening
• Mastocytic enterocolitis - a form of chronic diarrhea that does not respond to treatment
• Fluid in the abdomen (ascites)
• Bleeding from the GI tract
• Cytopenia (decrease in numbers of mature blood cells)
• Impairment of the liver and spleen
• Portal hypertension
• Easy bone fractures from osteoporosis
• Decreased quality of life
• Treatment-related complications

How is Mast Cell Leukemia Treated?

The treatment of Mast Cell Leukemia treatment depends on the severity of the condition, and on the age and health status of the individual. However, MCL is not known to respond to therapy.

• Avoiding and/or controlling the triggers that worsen the condition is important
• Antihistamine therapy may be recommended in some individuals
• In case of anaphylaxis, subcutaneous epinephrine or adrenaline may be administered
• Chemotherapy, radiation therapy, surgery including bone marrow/stem cell transplantation may be considered for leukemia
• In cases where the exact genetic cause is unknown or is not associated with C-KIT mutation, cytoreductive chemotherapy may be recommended. This is the treatment of mastocytosis with US FDA-recommended chemotherapy drugs
• Cytoreductive surgery may be an option for those with systemic forms of the condition. While surgery on the skin is considered relatively straightforward, this type of surgery for internal organs should be carefully considered and only performed by an experienced surgeon

Periodic monitoring or follow-up of the condition with the healthcare provider is recommended.

Note: Caution should be exercised while using non-steroidal anti-inflammatory medications (NSAIDs) such as Ibuprofen or naproxen. These medicines could cause upset stomach, as well as release of histamines, which could cause severe and adverse reactions.

How can Mast Cell Leukemia be Prevented?

Presently, it may be difficult to avoid Mast Cell Leukemia. However, some of the following factors may be considered:

• If there is a family history of the condition, then genetic testing of the expecting parents (and related family members) and prenatal diagnosis (molecular testing of the fetus during pregnancy) may help in understanding the risks better during pregnancy
• Identify, avoid, or control the triggers for systemic mastocytosis
• Limit exposure to radiation and industrial chemicals 
• Cessation of smoking
• Patients may be advised to carry injectable epinephrine to overcome serious allergic reactions

Some narcotics used in general anesthesia can cause mast cells to release their chemicals, including histamine, leading to shock. Patients must be told to inform all physicians of their mast cell disease to protect them from this. A ‘permanent’ passive reminder such as a MedicAlert device is strongly recommended.

What is the Prognosis of Mast Cell Leukemia? (Outcomes/Resolutions)

• The prognosis of Mast Cell Leukemia depends on the severity of the condition, and on the age and health status of the individual
• However, due to its aggressive nature and lack of response to appropriate treatment, the prognosis of MCL is extremely poor

Additional and Relevant Useful Information for Mast Cell Leukemia:

Recently, it has been shown that the chemicals released by mast cells also affect the activities of the bone cells. These include bone-building osteoblasts and bone-digesting osteoclasts. Mast cells have been linked to stimulation of osteoclasts and inhibition of osteoblasts, resulting in bone deficiencies.