A 21-year-old young girl presents with intense abdominal pain, nausea, diarrhea in the context of a cutaneous eruption formed by erythematous and papulous elements with brown violet aspect, very pruriginous, occasioned by the preparation of some fishmeal. Similar eruption debuted from childhood from the age of 4 year became rare with age. Since 3 years, the patient presents more intense digestive manifestation. The therapy with H2 antagonist (loratadine) and a mast cell stabilizer is beneficial over the digestive symptoms and in the same time cancel the pruritus and the erythema of the cutaneous lesions that remain hyperpigmented. The histopathological examination of a cutaneous lesion confirms the diagnosis of mastocytosis and the endoscopic examination discovers a duodenal ulcer and an erosive gastritis. The systemic mastocytosis is a rare disease, often associated with an urticaria pigmentosa, with difficult diagnosis in his absence. That's why, in patients with macular or nodular pigmented cutaneous lesions appeared in infancy and early childhood and which urticate in a characteristic manner when the skin is firmly rubbed, a cutaneous biopsy is necessary.