Case records of the Massachusetts General Hospital. Case 39-2007. A 5-month-old girl with skin lesions

How "benign" is cutaneous mastocytosis? A Danish registry-based matched cohort study

BACKGROUND

There are limited estimates of the incidence rates (IRs) of mastocytosis, and only a few studies have addressed the long-term consequences of living with these diagnoses. Previous reports have shown that systemic mastocytosis is associated with leukemic transformations and an increased risk of death as opposed to cutaneous mastocytosis (CM) and indolent systemic mastocytosis (ISM), which have benign diagnoses with life expectancy rates similar to those of the background population.

OBJECTIVE

This study aimed to analyze the incidence and mortality of mastocytosis.

METHODS

A population-based matched cohort study of patients with mastocytosis between 1 January 1, 1977 and 31 December 31, 2014 was identified from the Danish National Health Registries. IRs of CM, ISM, and pediatric mastocytosis were highlighted. Survival estimates were compared with those of a healthy background population, using a Cox proportional hazard model.

RESULTS

A total of 1461 patients with mastocytosis were identified. The annual IR of overall mastocytosis was 1.1 per 100,000 person years (95% confidence interval [CI], 1.0-1.2). Among children, the IR was 1.8 per 100,000 person years (95% CI, 1.6-2.1). The prevalence of any comorbidity was twice as high among patients with mastocytosis compared with the population without mastocytosis (odds ratio: 2.1; 95% CI, 1.8-2.5). The Charlson Comorbidity Index-adjusted mortality among adult patients with mastocytosis was HRCutaneous Mastocytosis 1.2 (95% CI, 0.8-1.9), HRIndolent Systemic Mastocytosis 1.9 (95% CI 1.4-2.5), and HRSystemic Mastocytosis 4.2 (95%, CI 1.9-9.4), respectively.

CONCLUSION

Based on an entire nation, with free health care at the point of access, we estimated an annual IR of mastocytosis and its subgroups. We discovered that patients with ISM had an increased risk of death compared with the general population. Our data supported the overall benign nature of CM diagnosed after age 2 years.

A simple case of a small elbow effusion

An 11-month-old child presented with what initially appeared to be 2 simple problems, a small elbow effusion followed 1 week later by croup. This case history is presented to remind emergency medicine physicians of the importance of index of suspicion and recognition of the difference between common events occurring in a normal host versus common events occurring in an abnormal host.