A mast cell is a resident cell of connective tissue that contains many granules rich in histamine and heparin. Specifically, it is a type of granulocyte derived from the myeloid stem cell that is a part of the immune and neuroimmune systems. Mast cells were discovered by Paul Ehrlich in 1877. Although best known for their role in allergy and anaphylaxis, mast cells play an important protective role as well, being intimately involved in wound healing, angiogenesis, immune tolerance, defense against pathogens, and vascular permeability in brain tumors.
Histamine is an organic nitrogenous compound involved in local immune responses communication, as well as regulating physiological functions in the gut and acting as a neurotransmitter for the brain, spinal cord, and uterus. Discovered in 1910, histamine has been considered a local hormone (autocoid) because it's produced without involvement of the classic endocrine glands; however, in recent years, histamine has been recognized as a central neurotransmitter. Histamine is involved in the inflammatory response and has a central role as a mediator of itching. As part of an immune response to foreign pathogens, histamine is produced by basophils and by mast cells found in nearby connective tissues. Histamine increases the permeability of the capillaries to white blood cells and some proteins, to allow them to engage pathogens in the infected tissues. It consists of an imidazole ring attached to an ethylamine chain; under physiological conditions, the amino group of the side-chain is protonated.
Hives, also known as urticaria, is a kind of skin rash with red, raised, itchy bumps. Hives may burn or sting. The patches of rash may appear on different body parts, with variable duration from minutes to days, and does not leave any long-lasting skin change. Fewer than 5% of cases last for more than six weeks. The condition frequently recurs.
Angioedema is an area of swelling (edema) of the lower layer of skin and tissue just under the skin or mucous membranes. The swelling may occur in the face, tongue, larynx, abdomen, or arms and legs. Often it is associated with hives, which are swelling within the upper skin. Onset is typically over minutes to hours.
Cold urticaria is a disorder in which large red welts called hives (urticaria) form on the skin after exposure to a cold stimulus. The hives are usually itchy and often the hands, feet and other parts of the body will become itchy and swollen as well. Hives vary in size from about 7 mm in diameter to as big as about 27 mm or larger.
Dermatographic urticaria is a skin disorder and one of the most common types of urticaria, affecting 2–5% of the population.
Tryptase is the most abundant secretory granule-derived serine proteinase contained in mast cells and has been used as a marker for mast cell activation. Club cells contain tryptase, which is believed to be responsible for cleaving the hemagglutinin surface protein of influenza A virus, thereby activating it and causing the symptoms of flu.
Aquagenic pruritus is a skin condition characterized by the development of severe, intense, prickling-like epidermal itching without observable skin lesions and evoked by contact with water.
Ketotifen is an antihistamine medication and a mast cell stabilizer used to treat allergic conditions such as conjunctivitis, asthma, and urticaria (hives). Ketotifen is available in ophthalmic and oral forms: the ophthalmic form relieves eye itchiness and irritation associated with seasonal allergies, while the oral form helps prevent systemic conditions such as asthma attacks and allergic reactions. In addition to treating allergies, ketotifen has shown efficacy in managing systemic mast cell diseases such as mastocytosis and mast cell activation syndrome (MCAS), which involve abnormal accumulation or activation of mast cells throughout the body. Ketotifen is also used for other allergic-type conditions like atopic dermatitis (eczema) and food allergies.
Urticaria pigmentosa (also known as generalized eruption of cutaneous mastocytosis (childhood type) ) is the most common form of cutaneous mastocytosis. It is a rare disease caused by excessive numbers of mast cells in the skin that produce hives or lesions on the skin when irritated.
Darier's sign is a change observed after stroking lesions on the skin of a person with systemic mastocytosis or urticaria pigmentosa.
Mast cell leukemia is an extremely aggressive subtype of acute myeloid leukemia that usually occurs de novo but can, rarely, evolve from transformation of chronic myeloid leukemia into the more aggressive acute myeloid leukemia. In a small proportion of cases, acute mast cell leukemia may evolve from a more progressive form of systemic mastocytosis. The diagnosis of acute mast cell leukemia by the WHO criteria includes the requirement for a prevalence of 20% neoplastic mast cells in marrow and 10% in blood. If the mast cells represent less than 10% of blood cells, the tumor is called "aleukemic" mast cell leukemia.
Solitary mastocytoma, also known as cutaneous mastocytoma, may be present at birth or may develop during the first weeks of life, originating as a brown macule that urticates on stroking. Solitary mastocytoma is a round, erythematous, indurated lesion measuring 1-5 cm in diameter. It can be mildly itchy or asymptomatic and develops over time. Predilection is the head and neck, followed by the trunk, extremities, and flexural areas.
Telangiectasia macularis eruptiva perstans (TMEP) is persistent, pigmented, asymptomatic eruption of macules usually less than 0.5 cm in diameter with a slightly reddish-brown tinge.
One of the most prevalent forms of adverse drug reactions is cutaneous reactions, with drug-induced urticaria ranking as the second most common type, preceded by drug-induced exanthems. Urticaria, commonly known as hives, manifests as weals, itching, burning, redness, swelling, and angioedema—a rapid swelling of lower skin layers, often more painful than pruritic. These symptoms may occur concurrently, successively, or independently. Typically, when a drug triggers urticaria, symptoms manifest within 24 hours of ingestion, aiding in the identification of the causative agent. Urticaria symptoms usually subside within 1–24 hours, while angioedema may take up to 72 hours to resolve completely.
X-linked reticulate pigmentary disorder is a rare X-linked genetic condition in which males manifest multiple systemic symptoms and a reticulated mottled brown pigmentation of the skin, which, on biopsy, demonstrated dermal deposits of amyloid. Females usually only have linear streaks of hyperpigmentation.
Midostaurin, sold under the brand name Rydapt by Novartis, is a multi-targeted protein kinase inhibitor that has been investigated for the treatment of acute myeloid leukemia (AML), myelodysplastic syndrome (MDS) and advanced systemic mastocytosis. It is a semi-synthetic derivative of staurosporine, an alkaloid from the bacterium Streptomyces staurosporeus.
Mast cell activation syndrome (MCAS) is a term referring to one of two types of mast cell activation disorder (MCAD); the other type is idiopathic MCAD. MCAS is an immunological condition in which mast cells inappropriately and excessively release chemical mediators, resulting in a range of chronic symptoms, sometimes including anaphylaxis or near-anaphylaxis attacks. Primary symptoms include cardiovascular, dermatological, gastrointestinal, neurological, and respiratory problems.
Autoimmune urticaria, also known as chronic autoimmune urticaria, is a type of chronic urticaria characterized by the presence of autoantibodies in the patient's immune system that target the body's own mast cells, leading to episodes of hives (urticaria). This immunologically distinct type of urticaria is considered autoimmune because the immune system, which normally protects the body from foreign organisms, mistakenly attacks the body's own cells, causing inflammation and other symptoms.
A mastocytoma in dogs is a neoplasm (neoplasia) originating from mast cells in the domestic dog, which occurs mainly in the skin and subcutis. Mastocytoma are not only extremely common in dogs, but also tend to be much more malignant in them than in other animal species. The average survival time for malignant tumors is only four months, whereas for benign tumors it is over two years.
