Isolated primary immunoglobulin M deficiency


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Isolated primary immunoglobulin M deficiency

Immune system

General infections


Neonatal sepsis


Hypersensitivity reactions

Type I hypersensitivity

Food allergy



Type II hypersensitivity

Immune thrombocytopenic purpura

Autoimmune hemolytic anemia

Hemolytic disease of the newborn

Goodpasture syndrome

Rheumatic heart disease

Myasthenia gravis

Graves disease

Pemphigus vulgaris

Type III hypersensitivity

Serum sickness

Systemic lupus erythematosus

Poststreptococcal glomerulonephritis

Type IV hypersensitivity

Graft-versus-host disease

Contact dermatitis


Transplant rejection

Graft-versus-host disease

Cytomegalovirus infection after transplant (NORD)

Post-transplant lymphoproliferative disorders (NORD)


X-linked agammaglobulinemia

Selective immunoglobulin A deficiency

Common variable immunodeficiency

IgG subclass deficiency

Hyperimmunoglobulin E syndrome

Isolated primary immunoglobulin M deficiency

Thymic aplasia

DiGeorge syndrome

Severe combined immunodeficiency

Adenosine deaminase deficiency


Hyper IgM syndrome

Wiskott-Aldrich syndrome

Leukocyte adhesion deficiency

Chediak-Higashi syndrome

Chronic granulomatous disease

Complement deficiency

Hereditary angioedema


Immune system organ disorders


Ruptured spleen

Immune system pathology review

Blood transfusion reactions and transplant rejection: Pathology review

Immunodeficiencies: T-cell and B-cell disorders: Pathology review

Immunodeficiencies: Combined T-cell and B-cell disorders: Pathology review

Immunodeficiencies: Phagocyte and complement dysfunction: Pathology review


Isolated primary immunoglobulin M deficiency


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High Yield Notes

10 pages


Isolated primary immunoglobulin M deficiency

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External Links



Kara Lukasiewicz, PhD, MScBMC

Charles Davis, MD

Sam Gillespie, BSc

Tanner Marshall, MS

In isolated primary immunoglobulin M deficiency, there’s a decrease in the number of IgM antibodies in the blood, while the levels of other types of antibodies remain normal.

Let’s take a look at how B cells end up secreting different types of antibodies.

Each B cell is born in the bone marrow from a stem cell and develops its own B cell receptor, which sits on the cell surface.

The B cell receptor consists of two parts - a protein called CD79 that communicates with the rest of the cell and a membrane bound IgM or IgD antibody that can bind to an antigen.

An antigen is any substance recognized by that particular antibody.

Each antibody has two identical light chains and two identical heavy chains that combine into a Y shape.

So this Y-shaped antibody’s got two arms with identical tips, which is called the variable region.

This variable region contains an antigen binding domain that’s unique to that antibody.

Below the variable region, or toward the point where the arms meet, is the constant region where every member of an antibody class is identical – so all IgM antibodies have the same constant regions, but IgM and IgA constant regions are different.

And there are five classes of antibodies in total: IgM, IgG, IgA, IgE, and IgD class antibodies, and each one has a slightly different job.

For example, IgMs are part of B cell receptors, and are the first free-floating antibodies produced in an immune response.

They’re secreted as a pentamer, meaning there are five antibodies connected together, which provides many binding sites for grabbing antigens and taking them out of the blood.

Each antibody has complement protein binding sites on the heavy chains, so these IgM pentamers are also great at activating complement proteins, which help destroy and remove pathogens.


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