Cutaneous mastocytosis in childhood

Urticaria pigmentosa and systemic mastocytosis

Key Clinical Message

Additional investigations for systemic involvement should be initiated once the diagnosis of cutaneous mastocytosis has been established in an adult patient. A serum tryptase can serve as a screening test for systemic mastocytosis, and persistent elevations should prompt further investigations, such as bone marrow studies.

Abstract

Urticaria pigmentosa (UP) is the most common form of cutaneous mastocytosis, presenting as a wide variety of macroscopic appearances. Cutaneous mastocytosis in pediatric patients usually does not present with systemic involvement, but more than half of adult patients with cutaneous mastocytosis demonstrate systemic involvement. Currently, there is no guidance surrounding systemic testing in patients with UP. A 50-year-old Caucasian male was referred to the Clinical Immunology and Allergy clinic with a history of a rash. He initially presented to hospital 12 years prior with group A beta hemolytic streptococcus bacteremia treated with multiple different antibiotics. One week following discharge, he developed erythematous brown spots on his right leg which were flat, non-pruritic, and not painful. The rash later expanded to his trunk and extremities. A skin biopsy performed 2 years prior to referral to our clinic demonstrated urticaria pigmentosa. The CD117 immunohistochemical stain showed increased perivascular and interstitial mast cells in the superficial dermis. Darier's sign was negative on physical examination, and venom testing was also negative. Although he had no symptoms of systemic involvement, his serum tryptase was elevated at 47.6 ng/mL in the context of normal kidney and liver function. A skeletal survey was normal, and an abdominal ultrasound ruled out splenomegaly. Bone marrow biopsy demonstrated a mild increase in paratrabecular and perivascular atypical mast cells, in keeping with systemic mastocytosis. Adult patients with cutaneous mastocytosis have a high likelihood of having an underlying systemic mast cell disorder. Therefore, any patient presenting with characteristic skin findings should be investigated as having a cutaneous manifestation of systemic mastocytosis. This case demonstrates the utility of serum tryptase and its role in triggering additional investigations and guiding appropriate therapy.

COVID-19 Vaccines Are Safely Tolerated in Adolescents with Cutaneous Mastocytosis

INTRODUCTION

The management of the COVID-19 vaccine in children with mastocytosis is unclear due to a lack of data. In the current study, we aimed to evaluate the adverse reactions following COVID-19 vaccination in adolescents with cutaneous mastocytosis (CM).

METHODS

This study included 27 paediatric patients who were diagnosed with CM and were followed up in the paediatric allergy department of a tertiary care children's hospital.

RESULTS

The median (IQR) age of the patients at the time of COVID-19 vaccination was 180 (156-203) months. Forty-four per cent of patients were vaccinated with the COVID-19 vaccine. Among all participants, the vaccination rate was found to be higher in older children, those who had been diagnosed with MPCM, and those who had not been infected with COVID-19 (p = 0.019, p = 0.009, p = 0.002, respectively). A total of 23 doses of the COVID-19 vaccine, including two doses of Sinovac/CoronaVac and 21 doses of Pfizer/BioNTech, were administered to 12 paediatric patients with CM. One of the patients had a history of intense itch, erythematous urticarial plaques, and had an exacerbation of existing skin lesions within 24-48 h after both doses of Pfizer/BioNTech vaccination.

CONCLUSION

The COVID-19 vaccination of patients with CM in this series seems to be safe, and the rate of adverse events was comparable to that in the general population. These results found in adolescents with CM are in line with the existing evidence that CM does not preclude vaccination in children.

Urticaria: A Narrative Overview of Differential Diagnosis

Urticaria is an inflammatory skin disorder that may occur in isolation or associated with angioedema and/or anaphylaxis. Clinically, it is characterized by the presence of smooth, erythematous or blanching, itchy swelling, called wheals or hives, which greatly vary in size and shape and last less than 24 h before fading to leave normal skin. Urticaria is the consequence of mast-cell degranulation that can be caused by immunological or non-immunological mechanisms. From a clinical point of view, many skin conditions can mimic urticaria and their recognition is mandatory for a correct management and therapeutic approach. We have reviewed all of the main relevant studies which addressed differential diagnosis of urticarial, published until December 2022. The National Library of Medicine PubMed database was used for the electronic research. The present review offers a clinical narrative overview, based on the available literature, of the principal skin disorders that can be misdiagnosed as urticaria (mainly autoinflammatory or autoimmune disorders, drug-induced reactions, and hyperproliferative diseases). The aim of this review is to provide clinicians a useful tool for correctly suspecting and identifying all of these conditions.

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.

Mastocytosis in children: a single-center long-term follow-up study

BACKGROUND

Mastocytosis is a heterogeneous group of rare disorders characterized by the accumulation of clonal mast cells in organs such as the skin and bone marrow. The diagnosis of cutaneous mastocytosis (CM) is based on clinical findings, positive Darier's sign, and histopathology, if necessary.

METHODS

Medical records of 86 children with CM diagnosed during a 35-year long period were reviewed. Most patients (93%) developed CM during the first year of life (median age 3 months). Clinical features at presentation and during the follow-up period were analyzed. Baseline serum tryptase level was measured in 28 patients.

RESULTS

A total of 85% of patients had maculopapular cutaneous mastocytosis/urticaria pigmentosa (MPCM/UP), 9% had mastocytoma, and 6% had diffuse cutaneous mastocytosis (DCM). Boy to girl ratio was 1.1:1. Fifty-four of 86 patients (63%) were followed from 2 to 37 years (median 13 years). Complete resolution was registered in 14% of mastocytoma cases, 14% of MCPM/UP, and in 25% of DCM patients. After the age of 18, skin lesion persisted in 14% mastocytoma, 7% MCPM/UP, and 25% children with DCM. Atopic dermatitis was diagnosed in 9.6% of patients with MPCM/UP. Three of 28 patients had elevated serum tryptase. Prognosis in all patients was good, and there were no signs of progression to systemic mastocytosis (SM).

CONCLUSION

To the best of our knowledge, our results represent the longest single-center follow-up study of childhood-onset CM. We found no complications of massive mast cell degranulation or progression to SM.