Indolent systemic mastocytosis

What it is

From: Orphanet

A rare, usually benign, chronic, form of systemic mastocytosis (SM) characterized by an abnormal accumulation of neoplastic mast cells (MCs) mainly in the bone marrow (BM) but also in other organs or tissues such as preferably the skin.

Reported clinical features and what the terms mean

The following findings are associated with this condition in Orphanet. They are not a checklist for diagnosing yourself, and they do not all occur in every affected person. Some are examination, imaging or laboratory findings that cannot be recognised at home.

The frequency labels describe how often a finding was reported among people with the condition in the source. They do not give the chance that a person with that symptom has the condition. Definitions below reproduce HPO terminology; they explain the term, not the likely severity in an individual.

Abnormal mast cell morphology · Very frequent (99-80%)

Any structural anomaly of mast cells, which are found in almost all tissues and contain numerous basophilic granules and are capable of releasing large amounts of histamine and heparin upon activation.

Abnormal skin morphology · Very frequent (99-80%)

Any morphological abnormality of the skin.

Abnormality of bone marrow cell morphology · Very frequent (99-80%)

An anomaly of the form or number of cells in the bone marrow.

Increased proportion of CD25+ mast cells · Very frequent (99-80%)

An increased proportion of mast cells are positive for the cell surface marker CD25 (also called interleukin-2 receptor alpha chain).

Mastocytosis · Very frequent (99-80%)

The presence of an increased number of mast cells and CD34+ mast cell precursors in the body.

Abdominal cramps · Frequent (79-30%)

A type of abdominal pain characterized by a feeling of contractions and typically fluctuating in intensity.

Allergy · Frequent (79-30%)

An allergy is an immune response or reaction to substances that are usually not harmful.

Darier's sign · Frequent (79-30%)

A skin change elicited by briskly rubbing the skin lesion in urticaria pigmentosa (UP), whereby the area begins to itch and becomes raised and surrounded by erythema. Unlike other forms of dermatographism, Darier's sign refers to urtication that is limited to the UP involved areas and, as in this case, spares the skin unaffected by UP.

Flushing · Frequent (79-30%)

Recurrent episodes of redness of the skin together with a sensation of warmth or burning of the affected areas of skin.

Generalized abnormality of skin · Frequent (79-30%)

An abnormality of the skin that is not localized to any one particular region.

Increased serum mast cell beta-tryptase concentration · Frequent (79-30%)

An abnormally elevated concentration of total tryptase (alpha and beta tryptase) in the blood circulation.

Maculopapular exanthema · Frequent (79-30%)

A skin rash that is characterized by diffuse cutaneous erythema with areas of skin elevation. It may evolve to vesicles or papules as part of a more severe clinical entity. Different degrees of angioedema with involvement of subcutaneous tissue may also appear.

Osteoporosis · Frequent (79-30%)

Osteoporosis is a systemic skeletal disease characterized by low bone density and microarchitectural deterioration of bone tissue with a consequent increase in bone fragility. According to the WHO criteria, osteoporosis is defined as a BMD that lies 2.5 standard deviations or more below the average value for young healthy adults (a T-score below -2.5 SD).

Pruritus · Frequent (79-30%)

Pruritus is an itch or a sensation that makes a person want to scratch. This term refers to an abnormally increased disposition to experience pruritus.

Other findings in the same source

From: Orphanet

Additional reported features include Skin rash (Frequent (79-30%)); Urticaria (Frequent (79-30%)); Anaphylactic shock (Occasional (29-5%)); Hepatomegaly (Very rare (<4-1%)); Lymphadenopathy (Very rare (<4-1%)); Splenomegaly (Very rare (<4-1%)). This is a selected summary, not a complete description of the condition.

When it may begin

From: Orphanet

Adult; Elderly

Inheritance in the source

From: Orphanet

Not applicable

Frequency and the population described

From: Orphanet

Point prevalence: 1-5 / 10 000; Europe; Class only.

Which doctor should you see?

The suggested department for discussing Indolent systemic mastocytosis is Oncology, with a oncologist and relevant organ specialist as the relevant type of clinician. General physician / Family Medicine; paediatrician for children. Referral depends on symptoms.

Additional services that may be relevant, depending on the findings, include: Relevant organ specialist / Surgical Oncology as indicated.

This is an editorial referral starting point. The appropriate clinic depends on the person’s age, symptoms, previous diagnosis and local services. The first clinician can decide whether another specialty or a team is needed; a department label does not confirm the diagnosis.

How to prepare for an assessment

Bring a short timeline of the main symptoms: when they first appeared, whether they are constant or episodic, what seems to change them, and how they affect daily activities. Include previous reports, discharge summaries, current medicines and supplements, allergies, and any relevant family history. A dated record is more useful than trying to match every feature in an online article.

Ask the clinician what is already established and what remains uncertain. If a test is suggested, ask what question it answers, what its limitations are and how the result would change the next step. The information here is not an instruction to arrange every possible test. In children, bring growth, developmental and school information if it is relevant to the concern.

• Has the exact tumour type been confirmed, and is staging relevant?
• What is the goal of each proposed treatment option?
• How will side effects, daily function and supportive care be addressed?

Treatment discussions and follow-up

The material gathered for this draft does not provide a complete condition-specific treatment pathway for Indolent systemic mastocytosis. That gap does not mean that treatment is unavailable. A clinician needs to establish the diagnosis and review current guidance before recommending medicines, procedures, rehabilitation or other support.

Before leaving the appointment, clarify the next review date, who will communicate results, and whom to contact if the situation changes. Discuss difficulties with sleep, work, school, mobility, eating or emotional wellbeing when these are relevant. Practical support may require coordination between the treating clinician and other services.

The collected references do not establish a complete prevention or long-term outlook section for this entry. Missing information should not be interpreted as proof that prevention is impossible or that a particular outcome is inevitable. Ask what is known for the exact subtype, stage and personal circumstances, and which uncertainties remain.

When to seek emergency help

Severe breathing difficulty, collapse, new stroke-like symptoms, a seizure that is prolonged or repeated without recovery, uncontrolled major bleeding, or an immediate risk of self-harm require emergency help. In India, call 112 or reach the nearest emergency department. This is a general, non-exhaustive warning list; it is not a condition-specific triage tool.