Background Mastocytosis is characterized by the accumulation/proliferation of abnormal mast cells. The frequency of isolated cutaneous involvement in adults with mastocytosis has not been fully determined. The main objective of our study was to assess the frequency of isolated cutaneous mastocytosis (CM) in adults with mastocytosis skin lesions. The second objective was to compare the clinical, histological, biological and imaging features in patients with isolated CM and patients with systemic mastocytosis (SM). Methods We included all patients with histology‐proven mastocytosis skin lesions between January 2009 and December 2017. The mastocytosis diagnosis was made according to the international diagnostic criteria. All data were collected from a dedicated specific case report. Results Among 160 patients with mastocytosis skin lesions, 25 patients had isolated CM (15.6%), 105 had SM and 30 (18.7%) patients had undetermined mastocytosis. Skin KIT mutation (OR: 51.9, 95% CI: 3.9–678, P = 0.001) and high bone marrow tryptase (OR: 97.4, 95% CI: 10.3–915, P = 0.001) were strong predictors of SM. The prevalence of osteoporosis was higher in the SM population than in the isolated CM population. Moreover, a decrease in bone mineral density over a short period of follow‐up (1–2 years) was associated with SM. There were no differences between the two groups regarding the frequency of mast cell activation symptoms, the presentation of skin lesions, the number of mast cells in the dermis and the level of serum tryptase. We propose considering the KIT mutation status and bone marrow tryptase levels to aid the diagnosis of isolated CM in adult mastocytosis patients. Conclusion Only a small minority of adults with mastocytosis skin lesions has isolated cutaneous involvement. In 18.7% of mastocytosis cases, even complete workup does not allow for a precise classification of patients.

Síndrome de Percheron. A propósito de dos casos clínicosPalabras clave ▻ Síndrome de Percheron ▻ Infarto bitalámico simultáneo ▻ Arteria de Percheron Keywords ▻ Percheron syndrome ▻ Simultaneous thalamic infarction ▻ Percheron artery ResumenEl infarto bitalámico simultáneo es una presentación isquémica infrecuente. La arteria de Percheron, presente en un tercio de la población, vasculariza la región paramediana de ambos tálamos y mesencéfalo rostral. El diagnóstico es dificultoso, por lo que reconocer esta variante anatómica es importante, siendo su afectación la causa más frecuente de infartos bitalámicos. La resonancia nuclear magnética juega un papel fundamental en el diagnóstico. El tratamiento dependerá de la etiología subyacente. Se describen dos casos clínicos, con hipersomnia como síntoma común, en los que se llega al diagnóstico de infarto bitalámico secundario al compromiso de la arteria de Percheron. AbstractBilateral thalamic stroke is an infrequent ischemic presentation. The Percheron artery, present in a third of the population, vascularizes the paramedian region of both thalamus and rostral mesencephalon. The diagnosis is difficult, so recognizing this anatomical variant is important, being its affectation the most frequent cause of bilateral thalamic infarcts. Nuclear magnetic resonance plays a fundamental role in the diagnosis. The treatment will depend on the underlying etiology. Two clinical cases are described, with hypersomnia as a common symptom, in which the diagnosis of simultaneous thalamic infarction secondary to Percheron artery compromise is reached.

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