Inclusion Criteria:

1. Chronic stable symptomatic maculopapulous cutaneous mastocytosis or indolent systemic
mastocytosis with skin involvement and a positive Darier's Sign

2. Age between 18 and 65 years.

3. Female patients must be using a highly effective method of birth control (such as
implants, injectables, combined oral contraceptives, some IUDs, sexual abstinence,
vasectomised partner), or they must be postmenopausal, surgically sterilised, or
hysterectomised.

4. Voluntarily signed written informed consent.

Exclusion Criteria:

1. The presence of permanent severe diseases, especially those affecting the immune
system, except for mastocytosis

2. History or presence of epilepsy, significant neurological disorders, cerebrovascular
attacks or ischemia

3. History or presence of myocardial infarction or cardiac arrhythmia which requires
drug therapy, hyper-/hypokalemia, bradycardia < 50bpm, QTc interval > 440ms

4. Evidence of severe renal dysfunction (creatinine > 1,5 x upper reference value)

5. Evidence of significant hepatic disease (liver enzymes > 2 x upper reference value)

6. History of adverse reactions to RUP, or other ingredients of the IMP

7. Presence of active cancer which requires chemotherapy or radiation therapy

8. Aggressive systemic mastocytosis

9. History or presence of alcohol abuse or drug addiction

10. Participation in any clinical trial within 4 weeks prior to enrolment

11. Commitment to an institution in terms of § 40 Abs. 1 S. 3 Nr. 4 AMG

12. Intake of antihistamines or leukotriene antagonists within 7 days prior to the
beginning of the study

13. Intake of oral corticosteroids within 14 days prior to the beginning of the study

14. Use of depot corticosteroids or chronic systemic corticosteroids within 21 days
before beginning of the study

15. Pregnancy or breast-feeding