Mab – see Monoclonal antibodies (Mab).

MabThera Trade name of rituximab.

Macrophages Large, mostly single nucleus cells of 16–22 μm in diameter. They are usually formed from blood monocytes after their deposition in different tissues. Some of the normal macrophages deposited in certain organs, such as the lungs, can also directly undergo division. They are a component part of the mononuclear phagocytic system (MPS) and belong to the group of professional phagocytes constituting the basic component of natural (non-specific) immunity against pathogenic microorganisms (phagocytosis). They represent a heterogeneous population of cells in the human body and differ from each other in terms of development, functional activity, anatomic localisation and biologic function. They can be divided into normal and inflammatory cells. Macrophages of tissue (histiocytes), the liver (Kupffer’s cells), lungs (alveolar macrophages), serum fluid (pleural and peritoneal macrophages), skin (histiocytes, Langerhans’ cells) and other tissues belong to the group of normal macrophages. Inflammatory macrophages occur in inflammatory exudates where they have important effector (cell killing, matrix destroying) and regulatory (matrix regenerating) functions. They originate almost exclusively from blood monocytes.

MACTAR Patient Preference Disability Questionnaire The McMaster Toronto Arthritis Patient Function Preference Disability Questionnaire (MACTAR) is a functional index that measures change in impaired activities selected by each patient in a baseline interview and change in rheumatoid arthritis (RA) disease activity.

Magnesium (Mg) The fourth most common cation in the human body and the second most common intracellular cation. Magnesium is essential for the function of approximately 300 enzyme systems, transcription of deoxyribonucleic acid and proteosynthesis and is a natural antagonist of the calcium channels as well as being essential for bone mineralisation.

Magnetic resonance imaging MRI is a medical imaging technique based on the effect that hydrogen protons in tissues exposed to an external magnetic field produce a rotating magnetic field (so-called spin) detectable by the scanner. Externally, tissues show different sizes of magnetic torque, the vector of which is oriented identically with the vector of the magnetic field. To measure this magnetic torque, it must be diverted by magnetic impulse, the energy of which is absorbed by protons and a resonance can be detected. Thereby, the longitudinal tissue resonance decreases and transverse tissue resonance increases. When the electrical impulse is discontinued, relaxation occurs (T1 longitudinal relaxation time, T2 transverse relaxation time). Imaging of tissues is based on the difference of these times in tissues and assigned intensity of grey (black/white scale). It does not use a noxious ionising radiation for imaging.

Major histocompatibility complex (MHC) One of many histocompatibility systems, it holds a dominant position amongst the given animal species. It is a system of genes whose products are strong transplant antigens. Typical features of MHC are its complexity and polymorphism, the ability of its molecules to regulate the immune response and induce a reaction in mixed-lymphocyte cultures (MLC), with membership of the immunoglobulin superfamily and responsibility for the immunochemical uniqueness of every individual in the population. The human MHC is referred to as the HLA complex.

Marfan’s syndrome (Antoine Marfan, French paediatrician, 1858–1942) An autosomal dominant disorder affecting the bones and connective tissue. The genetic defect is localised on chromosome 15 resulting in impairment of collagen and glycoprotein synthesis. In the clinical picture, affected individuals are tall and very slim with thin extremities (dolichostenomely) and typical prolonged lower part of the body and fingers (arachnodactyly). Hyperextensibility of the fingers and high-arched palate are typical. Pectus excavatum or pectus carinatum may be present. Component parts of the clinical picture include ophthalmic and cardiovascular complications. Ophthalmic complications include lens ectopy, myopia and iris vibration. Cardiovascular complications include dilatation of the aorta and aortal valve insufficiency, as well as mitral valve prolapse, dissection of the aorta, pulmonary artery dilatation, arrhythmias and even heart failure. Genetic counselling is important as there is a 50 % risk of inheritance of the disease to any offspring, and pregnancy in patients with Marfan’s syndrome is a high risk due to cardiac complications.

Markers of osteoformation Bone matrix precursors, in particular type I collagen, osteocalcin, sialoproteins and bone alkaline phosphatase isoenzyme, are formed in osteoblasts and excreted into the extracellular space. Here, collagen fibres are formed accompanied with the production of lamellar osteoid with interfibre bonds. This is the final stage of the ripening of bone matrix, which is subsequently mineralised. When evaluating the bone formation intensity, out of the many potential laboratory parameters, the procollagen type I N-terminal propeptide (P1NP) has the best predictive value.

Markers of osteoresorption Bone resorption is ensured by osteoclasts that dissolve hydroxyapatite crystals and degrade bone matrix. Thus, the bone mass releases calcium, phosphorus, enzymes and products of organic matrix degradation, which can be measured in blood and urine. However, their bone mass specificity should be always considered. Most often, levels of products of collagen degradation – N-telopeptides (NTX) and carboxy-terminal collagen cross-links (CTX) are determined. Changes in their blood and urine concentrations help evaluate the effect of antiresorptive treatment already after a few months, i.e. before the change can be detected in densitometry exam.

Maroteaux–Lamy disease – see Mucopolysaccharidosis (MPS).

Mast cells A heterogenic population of cells varying in shape and size (diameter 10–30 μm) and containing numerous characteristic electron-microscopic dense granules in their cytoplasm. They occur predominantly in connective tissue, in mucosa, skin and around vessels. They have high affinity receptors for the Fc domains of IgE that result in their involvement in early-type allergic reactions (IgE mediated). Specific IgE, arising after the first contact of the individual with a certain allergen, binds to these receptors. During the second or subsequent contact, the allergen can bypass the IgE molecules and directly bind to mast cells, causing degranulation with release of histamine and other mediators of anaphylaxis. These mediators can also be released by anti-IgE antibodies and anaphylatoxins C3 and C5a for which there are specific receptors on the surface of mast cells.

M-cells (microfold cells) Specialised cells of the intestinal epithelium. They transport microorganisms and macromolecular components of food from the intestinal lumen to Peyer’s patches (aggregations of lymphoid tissue) where they present these components to antigen-presenting cells found on the basolateral side. M-cells have a filtering function for the presentation of intra-intestinal antigens and thereby are involved in the regulation of immune response induction at the level of mucosal immunity.

McCune–Albright syndrome (polyostotic fibrous dysplasia) A complex of polyostotic (rarely also monoostotic) fibrous dysplasia, pigmented skin macules of ‘café au lait’ type and overactivity of one or more endocrine glands constitute the McCune–Albright syndrome (Donovan James McCune, American paediatrician, 1902–1976, and Fuller Albright, American physician, 1900–1969). In a typical case, the endocrinopathy is represented by precocious puberty but can also include acromegaly, thyrotoxicosis, Cushing syndrome, hyperprolactinaemia or hyperparathyroidism. The loss of phosphate may then result in hypophosphataemic disease reminiscent of oncologic rickets, but unlike it, the disease is caused by inhibition of phosphate transport by intestinal mucosa cells, not by the renal tubules. Endocrine hyperfunction is basically caused by overactivity of the target organ. An aromatase inhibitor and testosterone were used to suppress early puberty in females; treatment with medroxyprogesterone has also been reported. Calcitriol and phosphate supplementation in associated hypophosphataemic bone disease may eventually improve the X-ray picture of rickets, but it is not routine practice. Administration of pamidronate in McCune–Albright syndrome improved clinical symptoms, particularly pain and associated gait disturbance.

McMaster Toronto arthritis patient preference disability index (MACTAR) – see Instruments of assessing (health status measurements, outcome measurement) and MACTAR Patient Preference Disability Questionnaire.

MCTD – see Mixed connective tissue disease (MCTD).

Mechanical therapy Utilisation of mechanical instruments and appliances for medical treatment. These include certain active and passive body movements or parts of the body with traction, extension, massage, stationary bicycle, walking machine, etc.

Melsack’s questionnaire – see Algometry (evaluation of pain threshold).

Membrane immunoglobulin The molecule of immunoglobulin whose C-ends of heavy chains are prolonged by a hydrophobic tail consisting of 20 amino-acid units. Thereby, the molecule is embodied in the cytoplasmic membrane of B lymphocytes, where it becomes a component of the B cell antigen receptor complex (Ig-α/Ig-β antigen receptor). Particularly IgD and IgM monomers possess this attribute.

Meralgia paresthetica A clinical syndrome of burning pain, pins and needles and dysethesias on the anterolateral side of the thigh caused by compression of nervus cutaneus femoris lateralis. In majority of cases, the nerve compression occurs on the passing spot under the groin ligament close to spina iliaca anterior superior. This syndrome is more often seen in obese persons, diabetic patients and pregnant women or when wearing a tight belt. Difficulties usually disappear spontaneously. Analgesic and glucocorticoid injections may be effective. Antiepileptic drugs are used to relieve neuropathic pain. Exceptionally, it is necessary to perform surgical nerve decompression.

Mesna – see Cyclophosphamide.

Methotrexate As a medical agent, methotrexate was first described in 1946 and then administered in children with leukaemia in 1948. It was first successfully used in rheumatoid arthritis (RA) and psoriatic arthritis (PsA) in 1951, but the FDA only approved MTX for PsA treatment in 1971 and for RA treatment even later in 1988. However, the 1980s was a period of increased concerns over MTX, which resulted in a large number of publications.