Thought the disease is seen far more often in adults, children can also have systemic mastocytosis (SM), explains a recent review published in The Journal of Allergy and Clinical Immunology: In Practice.
SM in children is rare; most children with mastocytosisMastocytosis Rare disease caused by the buildup of mast cells. Cutaneous mastocytosis primarily affects the skin and is more common in children, while systemic mastocytosis affects internal organs and is more common in adults. have the form that affects only the skin, called cutaneous mastocytosis (CM). The review’s authors noted that it’s not known how many children have SM, the form of mastocytosis that affects both the skin and organs inside the body.
Most children with SM have specific skin symptoms: small, uniform reddish-brown spots or bumps on their back, belly or limbs. Therefore, diagnosis usually begins with a careful skin exam.
A blood test for a protein called tryptaseTryptase A protein enzyme that is primarily produced by mast cells and stored in small pockets within the cells, known as granules. High levels of tryptase are a key indicator of SM. can help: levels above 20 ng/mL may suggest SM. Like adults, many children with SM carry a specific genetic mutation called KIT D816V, so doctors may also measure how much of this mutation appears in the blood. Rising tryptase levels or increasing amounts of KIT D816V — especially when skin spots worsen — should raise concern for SM.
An abdominal ultrasound is often helpful, because enlarged organs can be a sign of SM.
Read more about SM testing and diagnosis
Among children diagnosed with SM, the most common type is indolent SMIndolent SM A subtype of nonadvanced SM caused by the abnormal accumulation of mast cells in the bone marrow and other organs. Indolent SM accounts for around 90% of SM cases., which usually progresses slowly. Very rarely, children may develop more serious forms, including aggressive SMAggressive SM A subtype of advanced SM marked by a high mast cell burden that leads to organ damage. Aggressive SM accounts for less than 10% of SM cases., mast cell leukemiaMast cell leukemia The most severe subtype of SM, caused by the rapid buildup of immature mast cells in the bone marrow and blood. Mast cell leukemia accounts for less than 5% of SM cases and has a poor prognosis. or SM that occurs together with other blood cancers like acute myeloid leukemia.
Bone-related issues such as osteopenia or osteoporosis, which are frequently seen in adults with SM, “are uncommon in pediatric patients, but may also be underdiagnosed,” the researchers said.
To treat children with SM, doctors use medicines called tyrosine kinase inhibitors that are tailored to the child’s specific KIT gene variant.
Children with widespread skin disease, very high tryptase levels, severe symptoms, or a history of anaphylaxisAnaphylaxis A severe allergic reaction that can turn fatal without treatment. Patients with SM are at a higher risk of developing anaphylaxis. are usually prescribed an epinephrineEpinephrine Also called adrenaline, this hormone is used in emergency situations to reverse symptoms during a severe allergic reaction (anaphylaxis). autoinjector for safety.
Most children with mastocytosis — even those with SM — have a good long-term outlook, the researchers said.
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