A recent case report published in the journal Frontline Gastroenterology highlights that ongoing diarrhea and unexplained protein loss can be a warning sign of systemic mastocytosis (SM).
The case report describes a 67-year-old man who went to the emergency room with diarrhea, weight loss and a belly swollen with fluid. He was already living with a blood cancer called chronic myelomonocytic leukemia. Blood tests showed his protein levels were dangerously low: His albumin was 16 g/L, about half of what it should be, and his infection-fighting antibodies were low too.
Through several tests, doctors ruled out kidney, heart or liver problems. Because the patient’s stool contained high levels of a protein called alpha-1 antitrypsin, they suspected that protein was escaping through his stomach or intestines. This condition is called protein-losing enteropathy.
Sign up here to get the latest news, perspectives, and information about SM sent directly to your inbox. Registration is free and only takes a minute.
Doctors used small cameras to examine the man’s stomach, small intestine and colon from the inside, but saw nothing unusual. They then took some cells from the man’s colon and examined them under the microscope, and saw that the lining of his colon was packed with mast cells. A blood test showed his 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. level (a marker of mast cellMast cell A type of white blood cell produced in the bone marrow. They help defend against infections and play a key role in allergic reactions. In SM, mast cells become overactive and build up throughout the body. activity) was more than eight times higher than normal, and a bone marrow biopsyBone marrow biopsy A procedure to collect a sample of bone marrow using a needle. Often used to examine the characteristics of mast cells and diagnose SM. found the KIT D816V mutation. Together, these findings confirmed that he had SM and a blood cancer at the same time.
The case report authors note that SM “is an exceedingly rare cause of protein-losing enteropathy, with diagnosis requiring a high level of suspicion.”
Read more about SM testing and diagnosis
Doctors treated him with antihistaminesAntihistamines Medications that block the effects of histamine, the chemical found in mast cells that is responsible for many of the symptoms of SM, as well as many allergic reactions., medicine to calm his mast cells and midostaurin (a drug that stops abnormal mast cells from growing and dividing). His diarrhea slowed to twice a day with formed stool, his albumin rose to 29 g/L and his tryptase dropped to 55.1 µg/L.
This case is a reminder that diarrhea can have many different causes, and doctors shouldn’t settle on the first explanation, especially in someone who already has blood cancer.
It also shows the importance of taking small tissue samples and examining them under a microscope even when a camera exam of the gut shows nothing wrong.
