Oncology & Hematology Coding Alert

Make sure you have documentation for primary, secondary, and other mast cell disorders.

ICD-10-CM changes are fast approaching. Be prepared to include additional codes for mast cell activation disorders. It aligns with the clinical classifications followed in practice for mast cell activation conditions.

The Committee on Mast Cell Disorders of the American Academy of Allergy, Asthma and Immunology (AAAAI) in conjunction with The Mastocytosis Society, Inc. (TMS), proposed the addition of these codes for Mast Cell Activation Syndrome (MCAS). TMS also indicated in their submission to the CMC Coordination Committee that MCAS, in all of its forms, can cause tremendous suffering and disability due to symptomatology from daily mast cell mediator release and may not be as rare as previously thought.

You can look for more details on: http://www.cdc.gov/nchs/data/icd/Topic_packet_3_19_2014.pdf.

When you look at the documentation, you may find a diagnosis of monoclonal mast cell activation. This implies that the cells look alike and bear similar markers. In this case, you will have a new ICD-10-CM code D89.41 (Monoclonal mast cell activation syndrome).

What is monoclonal mast cell activation syndrome? Monoclonal mast cell activation syndrome is usually diagnosed by a bone marrow biopsy which shows monoclonal mast cells with specific mutations (example, D816V KIT mutation) and/or specific cell surface markers (example, CD25). This has been seen in patients with elevated baseline serum tryptase levels and in patients with unexplained episodes of anaphylaxis.

Your physician may find a trigger for the mast cell activation and document the same. The triggers can be an allergen, an inflammatory disorder, or a neoplasm. When you confirm the cause of mast cell activation in the documentation, you will find code D89.43 (Secondary mast cell activation).

What is secondary mast cell activation? Secondary mast cell activation is seen in allergic disorders, physical urticarial, and chronic autoimmune urticarial. Mast cell activation may also be associated with chronic inflammatory or neoplastic disorders.

Your physician may document that there are no mast cell abnormalities or monoclonal expansion and no external triggers have been identified for triggering the episodes of mast cell activation. When the cause of the mast cell activation is not known, you will turn to a new code D89.42 (Idiopathic mast cell activation syndrome).

What is idiopathic mast cell activation syndrome? Idiopathic mast cell activation syndrome is a diagnosis of exclusion. In other words, your physician will diagnose idiopathic mast cell activation syndrome when primary and secondary mast cell activation disorders as well as idiopathic anaphylaxis have to be ruled out.

In rare instances, there may be a patient with a diagnosis of other mast cell activation disorders like mast cell hyperplasia. In this case you will have code D89.49 (Other mast cell activation disorder). However, you may fail to find any clues in the documentation for the cause for mast cell activation. In that case, you will have code D89.40 (Mast cell activation, unspecified).

Note: For malignant mast cell tumors, you submit code C96.2 (Malignant mast cell tumor).

Editor’s note: You can read more about mast cell disorders and their classification in ‘Mast Cell Activation Syndrome: Proposed Diagnostic Criteria. Towards a global classification for mast cell disorders. J Allergy Clin Immunol. 2010 Dec; 126(6): 1099–104.e4.’ This is available at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3753019/.

Mast Cell Activation

Before you submit the new codes for mast cell activation conditions, make sure your physician is treating a case of mast cell activation. 

There are three essentials for the diagnosis of mast cell activation:

1. Clinical symptoms of mast cell activation: Some of the key symptoms of mast cell activation include acute urticaria (hives), flushing, itching, high blood pressure, headache, abdominal cramping, diarrhea, vomiting, and respiratory difficulty. 

2. Transient increase in serum tryptase levels or of another defined mast cell mediator: Other mediators may include histamine and PGD2.

3. Response to anti-mediator drugs: Complete response to some medications like glucocorticosteroids, cromolyn, cyclooxygenase inhibitors, leukotriene receptor blockers, 5-lipoxygenase inhibitors, or antagonists of certain cytokines may also be regarded as indirect evidence of mast cell activation.