42 - Mastocytosis Flashcards
Most cases of mastocytosis arise in
Children
Mast cells arise from the bone marrow as granular _____+ pluripotent progenitor cells
CD34
KIT (CD117)
_____, a type III tyrosine kinase is the product of the protooncogene c-kit located in chromosome 4q12
KIT
KIT is expressed on mast cells, as well as
Melanocytes
Primitive hematopoietic stem cells
Primordial germ cells
Interstitial cells of Cajal
Ligand of KIT
Stem cell factor
Crosslinking of KIT by SCF is essential for
Mast cell maturation
Other cytokines that are jmportant in regulating mast cell growth and differentiation
IL-3 IL-4 IL-6 IL-9 IFN-gamma
Mutations in _____ appear to play a central role in mastocytosis
c-kit
Mutations in this codon are most common in adults with mastocytosis
816
Classification of mastocytosis
Cutaneous mastocytosis Indolent systemic mastocytosis Systemic mastocytosis with an associated clonal hematologic non-mast-cell-lineage Aggressive systemic mastocytosis Mast cell leukemia Mast cell sarcoma Extracutaneous mastocytoma
Represent the majority of patients with mastocytosis
Cutaneous mastocytosis
Indolent systemic mastocytosis
Most children have cutaneous mastocytosis, which is manifested as
Urticaria pigmentosa
Systemic mastocytosis occurs mostly in adults, and _____ is the most common form
Indolent systemic mastocytosis
Frequently have evidence of impaired liver function, hypersplenism, and/or malabsorption, but do not have a distinctive hematologic disorder or mast cell leukemia; have rapidly increasing mast cell numbers and are difficult to manage medically
Aggressive systemic mastocytosis
Characterized by multiorgan failure and bone marrow smears demonstrating a greater than 20% mast cell population
Mast cell leukemia
Tumors with highly atypical and immature mast cells; have localized destructive growth
Mast cell sarcomas
Usually localized to the lung and consist of mature mast cells
Extracutaneous mastocytomas
Urticaria pigmentosa frequently appear on the
Trunk
Urticaria pigmentosa lesions in children vs adults
Children - 1-2.5 cm
Adults - 5 mm or less (much smaller)
Adult UP skin lesions are most numerous on the
Trunk and proximal extremities
Y/N: Skin involvement is more common in patients with more advanced forms of systemic mastocytosis (SM-AHNMD, ASM, or MCL)
No - less common
Solitary mastocytomas frequently appear on the
Distal extremities
Onset of solitary mastocytomas generally before
6 months of age
Scratching or rubbing skin lesions leads to urtication and erythema
Darier sign
Darier sign is readily demonstrated in _____, but often less pronounced in adult skin lesions
Childhood UP and mastocytomas
Seen almost exclusively jn infants
Diffuse cutaneous mastocytosis
Dermographism with formation of hemorrhagic blisters can occur in the first months to years of life in children with
Diffuse cutaneous mastocytosis
Seen almost exclusively in adults; appears as telangiectatic macules and patches without hyperpigmentation
Telangiectasia macularis eruptiva perstans
Complaints of fever, night sweats, malaise, weight loss, bone pain, epigastric distress, and problems in mentation (cognitive disorganization) often signal the presence of
Systemic mastocytosis
Extracutaneous disease is extremely uncommon in children, but when present _____ are the most frequent. _____ is the most common symptom
GI symptoms
Diarrhea
Systemic mastocytosis with an associated clonal hematologic non-mast-cell-lineage disease occurs almost uniquely in
Adults
Preformed mast cell mediators
Histamine
Heparin
Tryptase
Chymase
Newly synthesized mast cell mediators
Leukotrienes
Prostaglandins
Special stains for mast cells
Toluidine
Giemsa
Antitryptase
CD117
_____-tryptase is elevated in patients with systemic mastocytosis
Alpha
_____-tryptase can be detected in both mastocytosis patients and in allergic patients experiencing anaphylactic reactions
Beta
_____-tryptase levels are most commonly measured and correlate with the extent of mast cell disease
Total alpha and beta serum
Total serum tryptase levels of > _____ ng/mL are currently considered abnormal
20
Total serum tryptase levels also can provide an estimate of a patient’s overall mast cel burden, and thus serial measurements in adults every _____ may prove useful in following disease progression
6-12 months
Major urinary metabolite of histamine
1,4-methylimidazole acetic acid
Next most common urinary histamine metabolite
Methylhistamine
Foods high in histamine content
Spinach
Eggplant
Cheeses
Red wines
Bones most commonly affected in SM
Proximal long bones Skull Spine Ribs Pelvis
More sensitive but less specific than routine radiographs
Skeletal scintigraphy (bone scan)
Reasonable preliminary test for detecting bone involvement in mastocytosis
Radiographs of the skull, spine and pelvis
Y/N: The bone marrow is often involved in patients with systemic mastocytosis
Yes
A bone marrow biopsy in childhood-onset disease is not recommended unless there is
Evidence of systemic involvement and/or
Unexplained peripheral blood abnormalities
Roentgenographic abnormalities of the GI tract fall into 3 major categories
- Peptic ulcers
- Abnormal mucosal patterns such as mucosal edema, multiple nodular lesions, coarsened mucosal folds, or multiple polyps
- Motility disturbances
Initial evaluation of a prepubertal child with mastocytosis
Does not require extensive testing
Presence of noncutaneous signs and symptoms or disease onset in adolescents or adults necessitates
CBC with differential Liver function test Total serum tryptase level Skeletal radiographs Bone marrow biopsies (recommended by some clinicians for all adult mastocytosis patients)
Characterized by symptoms of mast cell mediator release but lack the evidence of unregulated mast cell proliferation
Nonclonal mast cell activation syndrome
In patients with flushing, the diagnosis of _____ should be considered
Carcinoid tumor or pheochromocytoma
Carcinoid tumor or pheochromocytoma excrete increased amounts of
5-hydroxyindoleacetic acid
Patients with ISM who have evidence of hepatosplenomegaly, lymphadenopathy, and/or serum tryptase levels of > 200 ng/mL
Smoldering SM
First line topical treatment for CM
Topical glucocorticoids
Second line topical treatment for CM
Avoidance of triggering factors such as heat, friction, or drugs
H1 with or without H2 antihistamines
Second-generation H1 antihistamines
Cetirizine
Loratadine
Fexofenadine
Advantages of second-generation vs first-generation H1 antihistamines
Longer half-lives
More specific activity on the H1 receptor
Tricyclic antidepressant with potent H1 activity
Doxepin
Doxepin should be used with caution in older patients because it can cause
Cardiac QT interval prolongation
Antihistamines with potential mast-cell stabilizing properties
Ketotifen
Azelastine
H2 antihistamines
Cimetidine
Ranitidine
Famotidine
Nizatidine
Appears to be the treatment of choice in patients with advanced mastocytosis
2-chlorodeoxyadenosine
May limit the use of 2-chlorodeoxyadenosine
Myelosuppression
First-generation tyrosine kinase inhibitor
Imatinib
Second-generation tyrosine kinase inhibitors
Dasatinib
Nilotinib
Multikinase inhibitor
Midostaurin
Reported to cure a mastocytosis patient who expressed only normal (wild-type) c-kit; ineffective in patients expressing KIT D816
Imatinib
Inhibit the in vitro growth of D816V-expressing mast cell lines
Dasatinib and nilotinib
Inhibits both wild-type and mutated c-kit
Midostaurin