Difficult Cases: Mast Cell Disorders NAIA Speaker: Joyce E. Yu, MD, FAAAAI Columbia University Medical Center Morgan Stanley Children’s Hospital, New York, NY Mentor: Cem Akin, MD, PhD, FAAAAI Harvard Medical School Brigham and Women’s Hospital, Boston, MA

Case #1 A 55 year old female referred for evaluation of a mast cell disorder Episodic flushing, abdominal pain, profuse diarrhea, hypotension 6 episodes of presyncope or syncope in 2.5 years No itching, hives, angioedema No association with foods, exercise or new medications Prior colonoscopy/EGD and endocrine workup at outside hospital negative (carcinoid, pheochromocytoma)

Case #1 PMH: Allergic rhinitis (pollen, dust mites, cat), asthma, splenectomy (after trauma), cholecystectomy Meds: Calcium and vitamin D Allergies: NKMA, no food, insect sting or latex allergy FH: Allergic rhinitis in brother and sister, venom allergy in sister SH: Teacher, no tobacco or alcohol ROS: Negative for fever, night sweats, weight loss, lymphadenopathy, jaundice

Physical Exam Gen: NAD, obese HEENT: mild turbinate edema CV: normal Lung: normal Abd: no organomegaly Lymph: no LAD Skin: no rashes

Q1. Urticaria pigmentosa (UP) is the most common physical exam finding in mastocytosis. Which of the following is a typical feature of UP? Commonly involves face and hands Commonly involves trunk and proximal parts of extremities Associated with itching at baseline Characterized by urticarial wheals lasting for <2 hours

Q1. Urticaria pigmentosa (UP) is the most common physical exam finding in mastocytosis. Which of the following is a typical feature of UP? Commonly involves face and hands Commonly involves trunk and proximal parts of extremities Associated with itching at baseline Characterized by urticarial wheals lasting for <2 hours

Urticaria pigmentosa UP is seen in 80% of patients with systemic mastocytosis It is a fixed hyperpigmented rash that can appear as macules, papules, or small nodules that can be reddish-brown or brown in color Spares sun-exposed areas Lesions may urticate with friction, heat, alcohol, stress (Darier’s sign) Lesions may also form blisters when rubbed or stroked

Laboratory evaluation of our patient Normal: CBC with differential, electrolytes, liver function, 24 hour 5-HIAA, serum VIP, calcitonin Food allergy skin and blood tests: negative Inhalant allergy testing: Positive for dust mites Colonoscopy and EGD: Normal (no mast cell stains were performed at outside hospital) Tryptase: 8 ng/ml (baseline), 14 ng/ml 3 hours after an attack

Q2. Which of the following statements is correct about tryptase levels in this patient (8 ng/ml at baseline, 14 ng/ml after an event)? The increase after the event is suggestive of mast cell degranulation The increase is within laboratory variability range and does not confirm mast cell activation Plasma histamine is a more sensitive marker of mast cell activation, and therefore the results are meaningless Neither value is greater than 20 ng/ml and therefore the results rule out mastocytosis

Q2. Which of the following statements is correct about tryptase levels in this patient (8 ng/ml at baseline, 14 ng/ml after an event)? The increase after the event is suggestive of mast cell degranulation The increase is within laboratory variability range and does not confirm mast cell activation Plasma histamine is a more sensitive marker of mast cell activation, and therefore the results are meaningless Neither value is greater than 20 ng/ml and therefore the results rule out mastocytosis

Tryptase is the best validated marker of mast cell burden and activation Primarily produced by mast cells Smaller quantities by basophils and myeloid progenitor cells Baseline levels correlate with mast cell burden Mast cells spontaneously release alpha and beta protryptases which contribute to baseline levels Median level is 5 ng/ml Normal level can be up to 11.4 ng/ml Baseline levels >20 ng/ml is a minor diagnostic criterion for mastocytosis Increased transiently in systemic anaphylaxis Due to release of mature (mostly beta) tryptase stored in granules Half life of about 1 hr Needs to be checked within 3-4 hours after the event Meaningful increase: Baseline + 2 ng/ml + 20% of baseline

Case #1 Due to unexplained symptoms and elevated tryptase levels after an event the patient was recommended to have a bone marrow biopsy and aspiration Bone marrow biopsy (initial report): Normocellular marrow Scant mast cells with occasional spindle shaped forms Negative for mastocytosis

Case #1 Despite the initial pathology report, due to persistent clinical suspicion, CD25 staining was requested Positive on scattered mast cells C-kit mutational analysis in bone marrow aspirate came back positive for D816V mutation

Q3. What is the most appropriate diagnosis for this patient? Indolent systemic mastocytosis Aggressive systemic mastocytosis Monoclonal mast cell activation syndrome (MMAS) Idiopathic anaphylaxis

Q3. What is the most appropriate diagnosis for this patient? Indolent systemic mastocytosis Aggressive systemic mastocytosis Monoclonal mast cell activation syndrome (MMAS) Idiopathic anaphylaxis

Disorders associated with mast cell activation Primary (clonal mast cells) Systemic mastocytosis Monoclonal mast cell activation syndrome Secondary IgE mediated Non-IgE mediated: autoimmune disorders, reactions to vancomycin, physical urticaria Idiopathic Includes idiopathic anaphylaxis, urticaria/angioedema and mast cell activation syndrome

Diagnostic Criteria for Systemic Mastocytosis Systemic mastocytosis: 1 major + 1 minor or 3 minor MMAS: 1-2 minor clonality criteria* Major Multifocal clusters of mast cells (>15 MC per cluster) in bone marrow or GI tract Minor Spindle shaped mast cells in >25% of the infiltrate Baseline tryptase >20 ng/ml Codon 816 c-kit mutation* Aberrant CD25/CD2 expression on mast cells*

Comparing Bone Marrow Lesions in Mastocytosis and MMAS* * Tryptase-positive mast cells (Brown) Systemic Mastocytosis: Several clusters of mast cells Spindle-shaped mast cells Monoclonal Mast Cell Activation Syndrome: Very few clusters of mast cells Spindle-shaped mast cells

Classification of Mastocytosis Cutaneous mastocytosis (mainly diagnosed in children) Involves only skin (no bone marrow or GI involvement) UP (most common) Diffuse cutaneous mastocytosis Solitary mastocytoma Systemic mastocytosis (bone marrow aspirate and biopsy are required to assess bone marrow involvement) Indolent SM-AHNMD (associated hematologic clonal non-mast cell disease: commonly myeloproliferative or myelodysplastic disorders) Aggressive systemic mastocytosis C Findings = Liver, (ascites), GI (malabsorption), bone marrow dysfunction (cytopenias (Hgb <10, ANC <1000, or platelets < 100K), weight loss, splenomegaly Mast cell leukemia >10% MC in peripheral blood >20% in bone marrow smears

Case #1 Patient was placed on high dose H1 antihistamine, H2 antihistamine, oral cromolyn, montelukast, and prescribed self- injectable epinephrine No further syncopal episodes but continued to have flushing, abdominal pain and diarrhea requiring several ER visits Declined long term prednisone. No significant reponse to ketotifen or plaquenil

Q4. What is the most appropriate next management step? Cytoreductive therapy with imatinib Interferon alpha Allergen immunotherapy to dust mites Omalizumab

Q4. What is the most appropriate next management step? Cytoreductive therapy with imatinib Interferon alpha Allergen immunotherapy to dust mites Omalizumab

Carter et al. JACI 2007:119:1550 The authors of the article referenced above demonstrate that omalizumab therapy reduced the frequency of anaphylactic episodes in 2 patients with systemic mastocytosis. The mechanism of how omalizumab decreases the anaphylaxis remains unclear.

Treatment of indolent systemic mastocytosis and MMAS includes: H1 and H2 antihistamines: Age appropriate doses may be used once or twice daily. E.g. loratidine, cetirizine, fexofenadine, desloratadine, diphenhydramine, hydroxyzine, raniditine, famotidine Self injectable epinephrine Oral cromolyn: Adult dose 200 mg PO QID Anti-leukotrienes: Age appropriate dose of montelukast, zileuton, zafirlukast Steroids: E.g. adult dose prednisone 5-10 mg daily maintenance ASA (if urinary 11-b-PGF2a is elevated and if patient’s tolerance is known): Adult dose 81 mg QD-325 mg BID Consider omalizumab: 300mg q4 weeks Mast cell cytoreductive therapy may be considered in recurrent life threatening mast cell activation symptoms: E.g. cladribine, IFN-α

Case #2 56 year old female referred for routine management of systemic mastocytosis Skin lesions of UP at 54 Urticate with heat and friction PMH: Ulcerative colitis ROS: Episodic abdominal pain and diarrhea, otherwise asymptomatic

Case #2 Lab evaluation: Tryptase 52 ng/ml CBC with diff, LFTs nl Colonoscopy with biopsy Transverse colon: 60 MC/HPF with clustering and CD25 expression, c/w involvement with SM Rectum: Chronic active colitis, normal mast cells Bone marrow biopsy Moderately hypercellular but no overt dysplasia or hematologic disorder 15% marrow space occupied by MC infiltrates D816V c-kit mutation positive

Case #2, follow up Patient remained largely asymptomatic except some intermittent fatigue Serial labs over time: Tryptase: 52, 80, 88, 144 ng/ml Hgb: 13, 12.8, 11, 9.6 g/dl Imaging Mild splenomegaly and mesenteric lymphadenopathy

Q5. What is the most appropriate category of this patient’s mastocytosis? Indolent systemic mastocytosis (ISM) Aggressive systemic mastocytosis (ASM) SM-AHNMD (SM with associated clonal hematologic non-mast cell lineage disease) MCL

Q5. What is the most appropriate category of this patient’s mastocytosis? Indolent systemic mastocytosis (ISM) Aggressive systemic mastocytosis (ASM) SM-AHNMD (SM with associated clonal hematologic non-mast cell lineage disease) MCL

Systemic mastocytosis: Natural course Progression from ISM to ASM is rare but can occur in ~3% of the cases Prognosis and survival rates with vary with the type of SM ISM patients have a better life expectancy than ASM patients Risk factors for progression Older age at diagnosis Absence of skin lesions Presence of c-kit D816V mutation in multiple hematopoietic lineages Hepatosplenomegaly Higher tryptase levels (>100 ng/ml)

Q6. What is the most appropriate next management step? Increase H1 antihistamines Omalizumab Mast cell cytoreductive therapy with cladribine Imatinib

Q6. What is the most appropriate next management step? Increase H1 antihistamines Omalizumab Mast cell cytoreductive therapy with cladribine Imatinib

Imatinib resistance in D816V+ mastocytosis Akin et al. J Allergy Clin Immunol. 2004 Jul;114(1):13-9 A - C-kit is a tyrosine kinase (TK) receptor B - In wild type Kit, ATP binds to the kinase domain of the receptor after dimerization by stem cell factor C - Imatinib (tyrosine kinase inhibitor) binds the enzymatic pocket to block ATP binding and thus receptor activation D - C-kit mutation D816V (90% of SM cases) confers resistance to imatinib by altering the binding site. Therefore, most SM patients are not candidates for imatinib

Cytoreductive therapy in mastocytosis Imatinib effective in: Rare D816V negative cases Chronic eosinophilic leukemia associated with mastocytosis, FIP1L1/PDGFRA positive Cladribine Nucleoside analog that intercalates into DNA to trigger apoptosis May be used in imatinib resistant cases Bone marrow suppression and immunosuppression are common side effects IFN-α May be useful in slowly progressing aggressive mastocytosis Side effects such as flu-like symptoms limit patient compliance Investigational tyrosine kinase inhibitor therapy Stem cell transplantation

Case #2, follow up Started on Cladribine Serial labs: Tryptase 144, 108, 81 ng/ml (in 3 months) HGB: 9.6, 11.3, 12 g/dl Skin lesions largely resolved Remains asymptomatic Future options may include investigational tyrosine kinase inhibitor

Mastocytosis: Special considerations Hymenoptera anaphylaxis is high (approx. 10% incidence) Hypotension without urticaria/angioedema after insect sting suggests underlying mastocytosis Requires life long venom immunotherapy Osteoporosis in approximately 30% of patients Screening bone densitometry Follow up with at least yearly tryptase and CBC with diff Trigger avoidance (variable): Heat, alcohol, stress, exercise, drugs (incl. opioids, NSAIDs, muscle relaxants, vancomycin)

Mast Cell Disorder Diagnosis Algorithm- When to consider a BM biopsy Thorough history and exam including food, medications, insect stings, latex, radiographic contrast media, exercise and skin evaluation No UP or IgE mediated trigger identified Hypotensive episode without urticaria/angioedema following insect sting Urticaria pigmentosa (new onset or existing) in an adult patient Tryptase level BM biopsy BM biopsy >20ng/mL <20ng/mL BM biopsy Hypotensive syncope or presyncope without urticaria or angioedema YES NO Consider measuring mast cell mediators for mast cell activation syndrome -24 h urine N-methylhistamine 11-b-PGF2a BM biopsy *BM biopsy should consist of staining for tryptase, CD117 ,CD25 and c-kit D816V mutation