Introduction:
Mastocytosis is the name given to a group of diseases characterized by the pathological proliferation of so-called mast cells, and mast cells in their storage material where they usually locate: the skin, mucous membranes, bone marrow and some internal organs. These are rare diseases, the prevalence of mastocytosis being less than 0.01%. The causes of mastocytosis are not known while the course is varied and depends on the patient’s age, type of disease, the affected organs, response to therapy and the presence of comorbid conditions. Atopic dermatitis is one of the most common allergic diseases of the skin, with an incidence of 10–20% in children and 1–3% of adults. The most common initial symptoms appear during the first year of life. The emergence of the disease involves a number of immune mechanisms. With atopic dermatitis may coexist with other allergic diseases, especially those related to the so-called atopic march.

Objective:
The aim of the study was to describe the case of 1.5-year-old boy diagnosed with the form of cutaneous mastocytosis coexistent with atopic dermatitis, which made the diagnosis of mastocytosis difficult.

Material and Methods:
Examination of the specific IgE by means of a mixed panel – paediatric, control examinations, i.e. abdomen ultrasound scan, periodic blood tests including blood count, and the above-mentioned case desk research.

Conclusions:
The histopathological examination enabled the right diagnosis to be made.