Treatment of systemic mastocytosis in an infant with midostaurin

[Mastocytosis in children]

Mastocytosis in children is a rare disease characterized by an abnormal accumulation of tissue mast cells. Mastocytosis in children presents with typical skin alterations that are classified as maculopapular cutaneous mastocytosis, diffuse cutaneous mastocytosis, or mastocytoma. Some patients also develop mast cell mediator symptoms, such as pruritus, flush, and anaphylaxis. In many children, the disease is characterized by a benign and usually self-limiting course; systemic mastocytosis with extracutaneous involvement and a chronic or progressive course is found only rarely. Therapeutically, H1 antihistamines are primarily used on an as-needed basis or as continuous treatment, depending on the severity. Children, parents and caregivers should be thoroughly educated about the clinical picture and possible trigger factors of mast cell mediator release. For children with extensive skin alterations and severe symptoms, the prescription of an epinephrine auto-injector is recommended for emergency treatment.

Updates in diagnosis and management of paediatric mastocytosis

PURPOSE OF REVIEW

Paediatric mastocytosis is a rare clonal disorder characterized by the overproduction and organ infiltration of mast cells. Symptoms are due to mast cell mediator release. Cutaneous mastocytosis is the most common presentation in children with systemic disease being rare. Our aim is to provide a practical guideline in differentiating subtypes of paediatric mastocytosis while providing actionable recommendations on diagnosis, clinical management, follow-up and prognosis.

RECENT FINDINGS

Longitudinal cohort studies of paediatric cutaneous mastocytosis have shown spontaneous remission with favourable prognosis. Hereditary alpha-tryptasemia may coexist with mastocytosis; thus, screening for this disorder is recommended. There is an emerging role for serum tryptase in asthma endotyping and potential for using therapeutic tryptase inhibitors.

SUMMARY

Morbidity in paediatric mastocytosis typically arises from symptoms secondary to mast cell mediator release. Prognosis for nonaggressive disease is typically favourable; however, risks for anaphylaxis and psychosocial morbidity may be underestimated. Symptomatic management and anticipatory guidance may help support patients and families throughout the disease course.

Tyrosine kinase inhibitors for the treatment of indolent systemic mastocytosis: are we there yet?

Indolent systemic mastocytosis (ISM) is the most prevalent form of systemic mastocytosis. Many patients with ISM suffer from mast cell (MC) mediator-related symptoms In a small number of patients, hematologic progression is seen in the follow up. In some patients with ISM, symptoms arising from MC-derived mediators including gastrointestinal symptoms, anaphylaxis, neuropsychiatric symptoms are kept under control with conventional mediator-targeting drugs or MC-stabilizing agents. However, in a substantial number of patients, the symptoms are refractory to such conventional therapy. For these patients, novel drugs and targeted approaches are considered. One reasonable approach may be to apply tyrosine kinase inhibitors directed against KIT and other key kinase targets expressed in neoplastic MC in ISM. Since MC in over 90% of all patients with typical ISM display the KIT D816V mutant receptor, clinically effective KIT-targeting drugs have to be active against this mutant form of KIT. The two such most effective and well-studied agents currently available are midostaurin and avapritinib. Other KIT-targeting drugs, such as imatinib or masitinib, are less effective or even non-effective against KIT D816V and are thus only recommended for use in patients with other KIT mutant forms (non codon 816 mutations) or with wild type KIT. In the present article, we review the current state in the treatment of ISM with tyrosine kinase inhibitors, with special emphasis on treatment responses and potential adverse effects. In fact, all of these agents also have unique and common adverse effects, and their use to treat ISM patients should be balanced against their toxicity and short and long term safety.

Pediatric Mastocytosis: An Update

Mastocytosis is a rare clonal disorder characterized by excessive proliferation and accumulation of mast cells (MC) in various organs and tissues. Cutaneous mastocytosis (CM), the most common form in children, is defined when MC infiltration is limited to the skin. In adults, the most common form is systemic mastocytosis (SM), characterized by MC proliferation and accumulation in organs, such as bone marrow, lymph nodes, liver, and spleen.1 Genetic aberrations, mainly the KIT D816V mutation, play a crucial role in the pathogenesis of mastocytosis, enhancing MC survival and subsequent accumulation in organs and tissues.2,3 CM includes three forms: solitary mastocytoma, maculopapular cutaneous mastocytosis (MPCM), and diffuse cutaneous mastocytosis (DCM). In most children with CM, skin lesions regress spontaneously around puberty; unfortunately, it is not always a self-limiting disease.4 Even if SM occurs occasionally, all children with mastocytosis require planned follow-up over time. Children with mastocytosis often suffer from MC mediator-related symptoms, the most common of which is itching, often triggered by rubbing the lesions. Management of pediatric mastocytosis is mainly based on strict avoidance of triggers. Treatment with H1 and H2 histamine receptor blockers on demand and the availability of epinephrine auto-injectors for the patients to use in case of severe anaphylactic reactions are recommended.

Molecular Background, Clinical Features and Management of Pediatric Mastocytosis: Status 2021

Pediatric mastocytosis is a heterogeneous disease characterized by accumulation of mast cells in the skin and less frequently in other organs. Somatic or germline mutations in the KIT proto-oncogene are detected in most patients. Cutaneous mastocytosis is the most common form of the disease in children. In the majority of cases, skin lesions regress spontaneously around puberty. However, in few patients, mastocytosis is not a self-limiting disease, but persists into adulthood and can show signs of systemic involvement, especially when skin lesions are small-sized and monomorphic. Children with mastocytosis often suffer from mast cell mediator-related symptoms. Severe hypersensitivity reactions can also occur, mostly in patients with extensive skin lesions and blistering. In a substantial number of these cases, the triggering factor of anaphylaxis remains unidentified. Management of pediatric mastocytosis is mainly based on strict avoidance of triggers, treatment with H1 and H2 histamine receptor blockers, and equipment of patients and their families with epinephrine auto-injectors for use in severe anaphylactic reactions. Advanced systemic mastocytosis occurs occasionally. All children with mastocytosis require follow-up examinations. A bone marrow investigation is performed when advanced systemic mastocytosis is suspected and has an impact on therapy or when cutaneous disease persists into adulthood.

Pediatric mastocytosis

PURPOSE OF REVIEW

The current article highlights recent developments in the field of pediatric cutaneous mastocytosis. Mastocytosis is a spectrum of conditions that range from fleetingly benign to aggressively malignant. Through recognizing the natural progression of disease, the role of biomarkers and mutational analysis, treatment and risk of triggers, physicians can confidently stage, counsel and manage patients with pediatric cutaneous mastocytosis.

RECENT FINDINGS

Many lesions of cutaneous mastocytosis are chronic with some resolving around the mid-teenage years. KIT mutations are found in the majority of pediatric cutaneous mastocytosis but are not correlated with prognosis. Serum tryptase levels may be elevated in pediatric cutaneous mastocytosis patients without systemic mastocytosis. Pimecrolimus, omalizumab and tyrosine kinase inhibitors are effective treatment options. The low risk of NSAIDs and vaccinations has been characterized and epinephrine autoinjectors are rarely utilized in the pediatric cutaneous mastocytosis patient.

SUMMARY

Pediatric cutaneous mastocytosis is a heterogeneous disease with good outcome overall. Organomegaly, elevated tryptase levels and the presence of KIT mutation in peripheral blood may aid in the decision to pursue bone marrow biopsy. The armamentarium of treatments has expanded and better understanding of the significance of triggers and vaccination safety allows the clinician to thoughtfully counsel and allay anxiety around pediatric cutaneous mastocytosis.