Macrophagic Myofasciitis, is a rare muscle disorder characterized by microscopic lesions found in muscle biopsies.

Macular Pucker is scar tissue that has formed on the eye's macula/retina.

Mal de Debarquement Syndrome is a rare condition usually occurring after a cruise, aircraft flight, or other sustained motion event resulting in a persistent sensation of motion such as rocking, sw...

Malignant Hyperthermia is a rare disorder caused by exposure to certain drugs used for general anesthesia.

Malignant peripheral nerve sheath tumor (MPNST) is a rare cancer type that affects the protective tissue that surrounds the nerves that come out the spinal...

In osteopetrosis, osteoclasts do not function normally. Bone is deposited by osteoblasts, but not remodeled by osteoclasts. The results are dense hard bones that are actually more brittle because t...

Malonyl-Coenzyme A Decarboxylase Deficiency is a condition that prevents the body from converting some typs of fat to energy.

Mantle Cell Lymphoma is one of the rarer forms of non-Hodgkin's lymphoma.

Maple Syrup Urine Disease is a rare disorder resulting in the buildup of the branched-chain amino acids in the blood and urine.

Marden-Walker Syndrome is a rare disorder characterized by a distinct facial expression, a small or receding jaw, a cleft or high-arched palate, growth delay, bone joints in a fixed position and li...

Marfan Syndrome is a genetic disorder affecting roughly 200,000 Americans caused by mutations in the FBN1 gene.

MASA syndrome is a rare neurological disorder characterized by Mental retardation, Aphasia, Shuffling gait, and Adducted thumbs.

Mayer-Rokitansky-Kuester-Hauser (MRKH) syndrome is a rare condition characterized by the failure of the uterus and the vagina to dev...

McKusick-Kaufman Syndrome is a rare developmental disorder characterized by extra fingers and/or toes, heart defects, and genital abnormalities.

Meckel Syndrome is a rare genetic disorder.

MECP2 Duplication Syndrome is a rare brain disorder that causes severe intellectual disability, weak muscle tone, and seizures. It is caused by a duplication of the MECP2 gene.

The diaphragm is a structure made of muscle and fibrous tissue that separates the chest cavity from the abdominal cavity and aids with breathing. There are a few openings or hiatus in ...

Medullary Cystic Kidney Disease is a rare kidney disorder.

Medullary sponge kidney (MSK) is a congenital disorder developed from birth that affects the medulla or inner part of the kidneys. The kidneys’ function is to concentrate and fil...

Medullary thyroid carcinoma is a rare form of thyroid carcinoma that originates in the parafollicular C cells of the thyroid gland.

Megalencephaly Cutis Marmorata Telangiectatica Congenita is a rare disorder characterized by an enlarged brain.

Melanoma is a malignant tumor of melanocytes which are found predominantly in skin but also in the bowel and the eye

Melkersson–Rosenthal Syndrome is a rare neurological disorder characterized by reoccurring facial paralysis, swelling of the face and lips, and the development of folds and furrows in the tongue.

Melnick-Needles Syndrome is a rare genetic disorder of the bones, but also affects the soft body tissue such as the kidneys and the renal tract.

Complement 3 Glomerulopathy (C3G) is a rare disease caused by an overactive immune system, leading to deposit build-up in the kidneys and a decline in kidney function. There are two ty...

Meningiomas are the most common benign tumors of the brain.

Menkes syndrome is an inborn error of metabolism in which cells in the body cannot absorb enough copper.

MEPAN Syndrome is an ultra-rare neurodegenerative mitochondrial condition that is caused by mutations to the MECR gene. It results in impaired mitochondrial fatty acid synthesis and causes child...

MERRF Syndrome is a rare disorder that affects the function of the mitochondria.

Metachromatic Leukodystrophy is a rare lysosomal storage disease.

Metaphyseal Dysplasia is s a rare disorder in which the outer part of the shafts of long bones is unusually thin with a tendency to fracture.

Methylenetetrahydrofolate Reductase Deficiency (MTHFR) is a rare blood disorder and caused by mutations resulting in decreased enzyme activity.

Duplication of genes on chromosome location 22q11.2 causes a genomic disease known as microduplication 22q11.2 syndrome. The normal human genome has 23 chromosomes, 22 autosomes and 1 ...

Microscopic Polyangiitis is a rare autoimmune disease. This disease can affect many of the body's organ systems including (but not limited to) the kidneys, nervous system (particularly the peripher...

Miller-Dieker Syndrome (MDS) is a rare genetic condition, characterized by an abnormally smooth brain (lissencephaly), distinctive facial features, and neurologic abnormalities. MDS is caused by...

Minicore Myopathy is characterized by multiple small areas of disruption in the muscle.

Minimal Change Disease is a disease of the kidney usually affecting children.

Mitochondrial Diseases are a group of rare disorders relating to the mitochondria.

Mixed connective tissue disease (MCTD) is an autoimmune disorder that manifests symptoms from oth...

Moebius Syndrome is a rare congenital neurological disorder characterized by facial paralysis and the inability to move the eyes from side to side.

Molybdenum cofactor deficiency is a rare disorder characterized by progressive neurological deterioration. This condition is caused by genetic defects that lead to a reduction in the s...

Monomelic Amyotrophy is a rare lower motor neuron disorder that primarily affects young adult males in India and Japan.

Monosomy 21 is a rare disorder in which the 21st chromosome is missing from what should be a pair in every cell throughout the body.

Monosomy 9p is a rare disorder with the deletion of a portion of chromosome 9.

Morgellons is a condition characterized by a range of symptoms including crawling, biting, and stinging sensations on the skin; finding fibers on or under the skin; and persistent rashes or sores.

Morquio Syndrome, also known as Mucopolysaccharidosis IV (MPS IV), is a rare genetic disorder that affects the body’s skeletal development. Individuals with MPS lack the ability to break d...

Mosaic variegated aneuploidy (MVA) syndrome is a very rare condition characterized by problems with celldivision (specifically during mitosis) that...

MPPH (Magalencephaly, Polymicrogyria, Prodadactyly & Hydromcephalus) Syndrome.

Muckle-Wells syndrome (MWS) is an hereditary autoinflammatory disease with periodic fevers caused by mutations in the NLRP3 gene. It is considered a cryopyrin-associated syndrome (CAPS)...

Mucopolysaccharidosis Type I (MPS I), also known as Hurler Syndrome in its most severe form, is a rare inherited lysosomal storage disorder resulting from a deficiency of the enzyme al...

Mucopolysaccharidosis Type II (MPS II), commonly known as Hunter Syndrome, is a rare lysosomal storage disorder caused by a deficiency of the enzyme iduronate-2-sulfatase. This deficiency leads ...

Mucopolysaccharidosis III (MPS III), commonly known as Sanfilippo Syndrome, is a lysosomal storage disorder characterized by the accumulation of complex sugar molecules called glycosaminoglycans...

Muenke Syndrome is a disorder characterized by the premature closure of bones of the skull during development.

Multicentric Reticulohistiocytosis is a rare disorder characterized by the proliferation of immune cells, causing arthritis and skin nodules.

Multifocal Motor Neuropathy with Conduction Block is a rare disorder causing the destruction of the protective sheath around nerves.

Multiple endocrine neoplasia type 1 is a disorder in which multiple endocrine glands become overactive at the same time.

Multiple Endocrine Neoplasia Type 2A is a is hereditary syndrome characterized by medullary carcinoma of the thyroid, pheochromocytoma, hyperparathyroidism and occasionally cutaneous lichen amyloid...

Multiple endocrine neoplasia, Type 2B is a rare familial cancer syndrome caused by mutations in the RET proto-oncogene.

Multiple Epiphyseal Dysplasia is a rare cartilage and bone disorder.

Multiple Intestinal Lipomatosis is a rare disorder characterized by benign tumors in the intestinal tract.

Multiple Myeloma is a rare type of cancer of plasma cells. It is also known as bone marrow cancer or as one of the blood cancers.

Multiple Pterygium Syndrome is a rare genetic disorder characterized by facial anomalies, short stature, vertebral defects, and webbing of the neck, inside bend of the elbows, back of the knees, ar...

Multiple sclerosis (MS) is a neurological, autoimmune disorder of the central nervous system.  The immune system is the body’s defense against foreign materials such as viru...

Multiple System Atrophy is a rare neurodegenerative disease caused by cell loss in the brain imparing the autonomic nervous system and the motor system.

Multisystem proteinopathy (MSP) is an inherited degenerative disorder that affects multiple organ systems including the muscle, bone and the nervous system. The phenotypes of MSP encompass inclu...

Foundation to advocate for patients and families living with Multisystemic Smooth Muscle Dysfunction (MSMDS or SMDS), a disease caused by an ACTA2 genetic mutation.

MURCS Association is a rare disorder that affects females. MURCS stands for Mullerian, Renal, Cervicothoracic Somite abnormalities.

Congenital musclar dystrophy, severe myopia, brain involvement is "cobblestone" cortex with mental retardation and many other brain deformities.

Duchenne and Becker Muscular Dystrophy is a genetic condition characterized by progressive muscle weakness and atrophy which primarily affects the skeletal and heart muscles.

Myasthenia Gravis is an autoimmune disease that affects about 14-40 in every 1000 individuals. Individuals affected by Myasthenia Gravis produce an autoimmune response that blocks rece...

Mycobacterium avium complex (MAC) is a group of genetically related bacteria belonging to the genus Mycobacterium. It includes Mycobacterium avium and Mycobacterium intracellulare.

Mycobacterium Kansasii Olecranon Bursitis is a condition characterised by pain, swelling and inflammation of the olecranon bursa in the elbow caused by the bacterium mycobacterium kansasii.

Mycosis Fungoides is a rare form of cutaneous T-cell lymphoma (Non-Hodgkin lymphoma).

Myelodysplastic syndrome (MDS) is a group of cancers affecting blood cells. The term “myelodysplastic” comes from “myelo,” meaning marrow, and “dysplasia&...

There are three main types of cells in blood: red blood cells (RBCs), white blood cells (WBCs), and platelets. RBCs are responsible for the transport of gases such as oxygen and carbon...

Myoadenylate Deaminase Deficiency is a recessive genetic metabolic disorder characterized by the failure to deaminate the AMP molecules.

Myoclonus-Dystonia is a rare movement disorder characterized by rapid, brief muscle contractions and/or sustained twisting and repetitive movements that result in abnormal postures.

Myotonic Dystrophy Type 1 (DM1) is a degenerative muscle disorder that affects multiple body systems. The term myotonic means &ldq...

Myotubular Myopathy is a rare genetic disorder causing low muscle tone in the voluntary muscles.