Imatinib mesylate in the treatment of diffuse cutaneous mastocytosis

Diffuse Cutaneous Mastocytosis: A Current Understanding of a Rare Disease

Mastocytosis is a heterogeneous disease characterized by the expansion and accumulation of neoplastic mast cells in various tissues. Diffuse cutaneous mastocytosis (DCM) is a rare and most severe form of cutaneous mastocytosis, which typically occurs in childhood. There have been reports of a familial DCM with specific gene mutations, indicating both sporadic and hereditary factors involved in its pathogenesis. DCM is associated with severe MC mediator-related symptoms and an increased risk of anaphylaxis. The diagnosis is based on the appearance of skin lesions, which typically show generalized thickening, erythroderma, blistering dermographism, and a positive Darier's sign. Recognition, particularly in infants, is challenging due to DCMs resemblance to other bullous skin disorders. Therefore, in unclear cases, a skin biopsy is crucial. Treatment focuses on symptom management, mainly including antihistamines and mast cell stabilizers. In extremely severe cases, systemic steroids, tyrosine kinase inhibitors, phototherapy, or omalizumab may be considered. Patients should be equipped with an adrenaline autoinjector. Herein, we conducted a comprehensive review of literature data on DCM since 1962, which could help to better understand both the management and prognosis of DCM, which depends on the severity of skin lesions, intensity of mediator-related symptoms, presence of anaphylaxis, and treatment response.

[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.

Interobserver variability in the classification of childhood maculopapular cutaneous mastocytosis

BACKGROUND

Maculopapular cutaneous mastocytosis (MPCM) in children is classified in two variants: (i) monomorphic variant, presenting with the small macules or papules typically seen in adult patients; and (ii) polymorphic variant with larger lesions of variable size and shape, typically seen in children. The definition of polymorphic and monomorphic variants is mostly intuitive, and a validation of this classification has not been done.

OBJECTIVE

To study interobserver variability in the classification of MPCM in two groups of observers: mastocytosis experts and general dermatologists.

MATERIALS AND METHODS

Nineteen cases of childhood MPCM were shown blindly, for classification as monomorphic or polymorphic type, to 10 independent observers (eight dermatologists, one allergist and one haematologist) from Europe and North America with a vast experience in the management of paediatric mastocytosis. Also, the same cases were shown on a screen to 129 general dermatologists attending a meeting; their votes were registered by remote controls. The interobserver variability kappa coefficient (with 95% confidence interval) was calculated to measure the reliability of the correlation.

RESULTS

The value of kappa interobserver variability coefficient for the group of 10 experts (95% confidence interval) was 0.39 (0.18-0.63), which is considered as 'fair'. The value of kappa interobserver variability coefficient for the group of 129 general dermatologists (95% confidence interval) was 0.17 (0.06-0.39), which is considered as 'slight'. A complete agreement of all 10 experts was achieved in only four of 19 cases (21.1%) The most voted choice was concordant between the two groups in only 11 of the 19 cases.

CONCLUSIONS

We failed to validate the classification system of childhood MPCM in monomorphic and polymorphic types. While the rate of agreement was low for mastocytosis experts, it was nearly the agreement expected by chance in general dermatologists.

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: Recognition and Management

Mastocytosis is a heterogeneous group of disorders characterized by the accumulation of clonal mast cells in organs such as the skin and bone marrow. In contrast to adults, most affected children have only cutaneous involvement. This article reviews the molecular pathogenesis, skin findings, mast cell mediator-related symptoms, evaluation, and management of childhood-onset mastocytosis, noting differences from adult-onset disease. Current classification of cutaneous mastocytosis and the natural histories of different variants in pediatric patients are highlighted, with a focus on clinical manifestations with prognostic implications. A practical algorithm is provided to guide clinical assessment, laboratory and other investigations, and longitudinal monitoring, including recognition of hepatosplenomegaly as a marker of systemic disease and utilization of allele-specific quantitative PCR (ASqPCR) to detect KIT mutations in the peripheral blood. Updated information and consensus-based recommendations regarding possible triggers of mast-cell degranulation (e.g., physical, medications) are discussed, with an emphasis on patient-specific factors and avoiding excessive parental concern. Lastly, an individualized, stepwise approach to treatment of symptoms, skin-directed therapy, and potential use of kinase inhibitors for severe systemic disease is outlined.

Management of a neonate with diffuse cutaneous mastocytosis: Case report and literature review

Mastocytosis is an accumulation of clonal mast cells within tissues, commonly caused by mutations in the KIT proto-oncogene. This report describes the management of a neonate with diffuse cutaneous mastocytosis (DCM) caused by a rare activating KIT mutation, specifically internal tandem duplication of the Ala502Tyr503 pair on exon 9, and reviews current data regarding work-up of DCM in pediatric patients.

Feline maculopapular cutaneous mastocytosis: a retrospective study of 13 cases and proposal for a new classification

CASE SERIES SUMMARY

Cutaneous mastocytosis is a disorder rarely reported in veterinary dermatology and usually described as 'urticaria pigmentosa'. This study aimed to evaluate the diagnosis, treatment and outcome of 13 affected cats, selected from the files of a private referral dermatology practice within a period of 14 years. Breeds of the affected individuals included Sphynx (n = 9), Devon Rex (n = 2) and Sphynx/Devon Rex crossbreeds (n = 2). Females (n = 9) were over-represented and the median duration of clinical signs prior to diagnosis was 8 months. The clinical presentation of these 13 cats was compared with cases reported in the veterinary literature and classified according to the current human consensus on cutaneous mastocytosis. Three clinical forms could be distinguished in cats: (1) large papular lesions and wheals, typically localised to the head, shoulders, ventral neck and axillae, and which may spontaneously resolve (termed polymorphic maculopapular cutaneous mastocytosis); (2) erythematous dermatitis, characterised by small maculopapular lesions often associated with crusts and with a poorer prognosis (termed monomorphic maculopapular cutaneous mastocytosis); and (3) more chronic dermatitis characterised by lichenification and hyperpigmentation, similar to the human condition 'urticaria pigmentosa' (termed pigmented maculopapular cutaneous mastocytosis). Histopathology was performed in eight cases and revealed a superficial-to-deep dermatitis characterised by infiltrates of mast cells and eosinophils. The response to various treatments, including antihistamines, steroids and ciclosporin, was variable.

RELEVANCE AND NOVEL INFORMATION

This article reports 13 new cases of feline cutaneous mastocytosis, confirming the clinical presentation and apparent breed predisposition. The feline maculopapular cutaneous mastocytosis seems to be clinically very close to the human form. This study proposes a new classification system for the feline disease based on the current human consensus, clinical presentation and prognosis, with three different subforms: polymorphic maculopapular cutaneous mastocytosis with eventual spontaneous regression; monomorphic maculopapular cutaneous mastocytosis with chronic evolution; and pigmented maculopapular cutaneous mastocytosis.

Diffuse cutaneous mastocytosis: Case report and literature review

A 6-month-old boy was referred to our burn unit with a recurrent bullous dermatitis, fever, and emesis, originally diagnosed as staphylococcal scalded skin syndrome (SSSS) at an outside hospital. Infectious workup was negative and shave biopsy revealed a dense, diffuse dermal infiltrate of mast cells, consistent with diffuse cutaneous bullous mastocytosis-a rare variant of cutaneous mastocytosis. Treatment included a prolonged course of corticosteroids and antihistamines. Recognition of this rare form of mastocytosis is important, as it can be easily mistaken for other pediatric bullous diseases and is associated with life-threatening complications including vasodilation, anaphylactic shock, gastrointestinal bleeding, and death.

Cutaneous mastocytosis treatment: strategies, limitations and perspectives

Mastocytosis is a rare myeloproliferative disease, characterized by excessive proliferation and accumulation of mast cells in the tissues. In cutaneous mastocytosis (CM), mast cells infiltration is limited to the skin, whereas in systemic mastocytosis (SM) internal organs are involved. The first-line treatment in CM is antimediator therapy (mainly H1 and H2 antihistamines) and short-term topical corticosteroids. Phototherapy is the second-line therapy which may be considered when antihistamines do not produce the expected improvement. New therapeutic options include omalizumab and KIT-targeting agents. Although the disappearance of skin lesions has been reported as a result of cytoreductive therapies in SM, the use of potentially toxic drugs in CM is not recommended. In all adults with mastocytosis and in pediatric patients with severe CM, a persistently elevated serum tryptase level and anaphylaxis in medical history, equipping with epinephrine autoinjector for use in case of anaphylaxis is recommended.

Natural history and treatment of cutaneous and systemic mastocytosis

INTRODUCTION

Mastocytosis, a heterogeneous group of disorders, is characterized by an abnormal increase in the number of mast cells that is limited to the skin (cutaneous mastocytosis), involving extracutaneous tissues (systemic mastocytosis), or presenting as solid tumours (mastocytoma and mast cell sarcoma). Recent studies estimate that 1 in 10,000 people are diagnosed with mastocytosis. Although prompt diagnosis and appropriate management are crucial, little is known about the natural history and currently there are no established management guidelines. We have conducted a systematic review to assess the natural history and management of different mastocytosis subtypes.

METHODS

A systematic review and meta-analysis were conducted using the PubMed and Ovid database of studies published in English and French over the last fifteen years, from January 2001 to December 2016. Keywords 'Cutaneous mastocytosis', 'Systemic mastocytosis', 'pathophysiology', 'clinical course', 'prognosis', 'drug therapy', and 'therapy' were searched. Rate of complete resolution was subjected to pooled analysis for different mastocytosis subtypes. Meta-analysis was conducted using Stata version 12.0.

RESULTS

We reviewed 634 papers, of which 5 were included in the analysis of resolution, and 138 were included in the assessment of management. Pooled estimate for rate of complete resolution varied depending on the mastocytosis subtype. In cutaneous mastocytosis, the complete resolution rate for mastocytoma was 10% per year (95% CI: 4.8%, 15.1%) while the rate for urticaria pigmentosa was 1.9% per year (95% CI: -0.5%, 4.3%). Diffuse cutaneous mastocytosis and systemic mastocytosis subtypes did not show evidence of complete resolution in the studies reviewed. Treatment of cutaneous and systemic mastocytosis is purely symptomatic with topical corticosteroids, antihistamines, omalizumab and imatinib being common choices.

CONCLUSION

Rate of resolution of mastocytosis is only shown in urticaria pigmentosa and mastocytoma. Better management guidelines are required to improve the health of these patients.

Current approach to cutaneous mastocytosis in childhood

Mastocytosis is a heterogeneous disorder characterized by clonal proliferation and accumulation of mast cells in one of more organs which may lead to different clinical pictures. Pathological increase and activation of mast cells in various tissues can cause different clinical pictures. Cutaneous mastocytosis limited to the skin is the most typical clinical picture observed in children and systemic mastocytosis is very rare in the pediatric age group. The diagnosis of cutaneous mastocytosis is based on clinical findings, but is often delayed due to lack of clinical awareness of the disease and lack of its consideration in the differential diagnosis. This article focuses on the current diagnosis, management and treatment of cutaneous mastocytosis in children in order to increase awareness about this issue.

Imatinib in systemic mastocytosis: a phase IV clinical trial in patients lacking exon 17 KIT mutations and review of the literature

Resistance to imatinib has been recurrently reported in systemic mastocytosis (SM) carrying exon 17 KIT mutations. We evaluated the efficacy and safety of imatinib therapy in 10 adult SM patients lacking exon 17 KIT mutations, 9 of which fulfilled criteria for well-differentiated SM (WDSM). The World Health Organization 2008 disease categories among WDSM patients were mast cell (MC) leukemia (n = 3), indolent SM (n = 3) and cutaneous mastocytosis (n = 3); the remainder case had SM associated with a clonal haematological non-MC disease. Patients were given imatinib for 12 months -400 or 300 mg daily depending on the presence vs. absence of > 30% bone marrow (BM) MCs and/or signs of advanced disease-. Absence of exon 17 KIT mutations was confirmed in highly-purified BM MCs by peptide nucleic acid-mediated PCR, while mutations involving other exons were investigated by direct sequencing of purified BM MC DNA. Complete response (CR) was defined as resolution of BM MC infiltration, skin lesions, organomegalies and MC-mediator release-associated symptoms, plus normalization of serum tryptase. Criteria for partial response (PR) included ≥ 50% reduction in BM MC infiltration and improvement of skin lesions and/or organomegalies. Treatment was well-tolerated with an overall response rate of 50%, including early and sustained CR in four patients, three of whom had extracellular mutations of KIT, and PR in one case. This later patient and all non-responders (n = 5) showed wild-type KIT. These results together with previous data from the literature support the relevance of the KIT mutational status in selecting SM patients who are candidates for imatinib therapy.

Molecular changes associated with the development of resistance to imatinib in an imatinib-sensitive canine neoplastic mast cell line carrying a KIT c.1523A>T mutation

Although imatinib has therapeutic activity for certain subsets of patients with mastocytosis, it is not always curative. Here, molecular mechanisms that confer imatinib resistance to neoplastic mast cells were investigated using an imatinib-sensitive canine neoplastic mast cell line VI-MC carrying a KIT c.1523A>T activating mutation. Two imatinib-resistant sublines were established by culturing VI-MC cells in increasing concentrations of imatinib (1 μM resistant, rVI-MC1; 10 μM resistant, rVI-MC10). Both sublines had a second KIT mutation c.2443G>C. Recombinant KIT with the second mutation was insensitive to 1 μM but sensitive to 10 μM imatinib. The effect of imatinib on the phosphorylation of KIT and its downstream signalling proteins was then examined using these sublines. KIT and ERK were constitutively phosphorylated in both sublines, and their phosphorylation was suppressed by 10 μM imatinib in rVI-MC1 cells. However, KIT but not ERK phosphorylation was suppressed in rVI-MC10 cells. The phosphorylation of ERK in rVI-MC10 cells was also not diminished by the Src family kinase (SFK) inhibitor dasatinib. This second mutation in KIT may play an important role in imatinib resistance in neoplastic mast cells. Furthermore, KIT/SFK-independent activation of ERK would be involved in imatinib resistance when the neoplastic cells are exposed to higher concentrations of imatinib.

The care pathway for children with urticaria, angioedema, mastocytosis

Cutaneous involvement characterized by urticarial lesions with or without angioedema and itch is commonly observed in routine medical practice. The clinical approach may still remain complex in real life, because several diseases may display similar cutaneous manifestations. Urticaria is a common disease, characterized by the sudden appearance of wheals, with/without angioedema. The term Chronic Urticaria (CU) encompasses a group of conditions with different underlying causes and different mechanisms, but sharing the clinical picture of recurring wheals and/or angioedema for at least 6 weeks. Hereditary Angioedema (HAE) is a rare disorder characterized by recurrent episodes of non-pruritic, non-pitting, subcutaneous or submucosal edema affecting the extremities, face, throat, trunk, genitalia, or bowel, that are referred as “attacks”. HAE is an autosomal dominant disease caused by a deficiency of functional C1 inhibitor, due to a mutation in C1-INH gene (serping 1 gene) characterized by the clonal proliferation of mast cells, leading to their accumulation, and possibly mediator release, in one or more organs. In childhood there are two main forms of mastocytosis, the Systemic and the Cutaneous. The clinical features of skin lesions in urticaria, angioedema and mastocytosis may differ depending on the aetiologic factors, and the underlying pathophysiological mechanisms. The diagnostic process, as stepwise approach in routine clinical practice, is here reviewed for CU, HAE and mastocytosis, resulting in an integrated method for improved management of these cutaneous diseases. Taking into account that usually these conditions have also a relevant impact on the quality of life of children, affecting social activities and behavior, the availability of care pathways could be helpful in disentangle the diagnostic issue achieving the most cost-effective ratio.

Symptomatic response to imatinib mesylate in cutaneous mastocytosis associated with chronic myelomonocytic leukemia

Mastocytosis is an uncommon disorder defined by increased and abnormal mast cells in one or more tissues. Cutaneous mastocytosis (cm) is limited to the skin, with varying degrees of rash, pruritus, and disfigurement. Systemic mastocytosis (sm) typically involves the bone marrow, sometimes in association with other bone marrow disorders, including chronic myelomonocytic leukemia (cmml). Mastocytosis has been associated with somatic mutations in the gene encoding the tyrosine kinase Kit, leading to identification of Kit as a therapeutic target. The Kit inhibitor imatinib mesylate is approved for aggressive sm. We present an unusual patient with disabling pruritus from telangiectasia macularis eruptiva perstans, a subtype of cm, and cmml, but with no evidence of systemic mast cell disease. She was treated with imatinib and experienced marked improvement in her pruritus. Concomitant cm and cmml have not previously been reported, and the present report is the first of successful imatinib therapy in an adult patient with cm.