Large maculopapular cutaneous lesions are associated with favorable outcome in childhood-onset mastocytosis

Background: Mastocytosis, characterized by pathologic accumulation of mast cells, can manifest itself in adulthood or childhood. Pediatric patients usually have cutaneous mastocytosis (CM) with mast cell infiltrates limited to the skin and spontaneous improvement of skin lesions after several years. However, there are some patients with persistent disease resembling adulthood-onset mastocytosis. Objective: The current classification of CM differentiates between 3 subforms. In clinical practice we noticed that different variants of these subforms might exist, particularly in patients with childhood-onset mastocytosis. Therefore, in the present study, we aimed to investigate whether specific cutaneous lesions in patients with childhood-onset mastocytosis are associated with other disease parameters. Methods: We analyzed 144 patients with a disease onset of less than age 17 years using a systematic dermatologic approach. Results: One hundred twenty-two patients presented with maculopapular cutaneous mastocytosis (MPCM), 12 patients presented with diffuse CM, and 10 patients presented with solitary mastocytoma of the skin. Patients with MPCM showed particularly heterogeneous cutaneous lesions and were therefore grouped into 3 variants presenting either with small lesions (MPCM-small, skin lesions < 1 cm in diameter; n = 19), large lesions (MPCM-large, skin lesions >= 1 cm in diameter; n = 89), or atypical lesions (MPCM-other, n = 14). Patients with MPCM-large lesions, compared with those with MPCM-small lesions, were characterized by significantly lower tryptase levels, shorter disease duration, and earlier disease onset. In addition, more patients with MPCM-large lesions exhibited spontaneous regression of cutaneous lesions. Conclusion: Our data show that patients with MPCM-large lesions compared with those with MPCM-small lesions have a more favorable disease course and suggest exploring the size of cutaneous lesions as a prognostic parameter in childhood-onset MPCM.