Complement 2 deficiency is a type of
complement deficiency caused by any one of several different alterations in the structure of
complement component 2
Complement C2 is a protein that in humans is encoded by the ''C2'' gene. The protein encoded by this gene is part of the classical pathway of the complement system, acting as a multi-domain serine protease. Deficiency of C2 has been associated wit ...
.
It has been associated with an increase in
infection
An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable dis ...
s.
It can present similarly to
systemic lupus erythematosus (SLE).
Signs and symptoms
C2D is linked to
bacterial infections
Pathogenic bacteria are bacteria that can cause disease. This article focuses on the bacteria that are pathogenic to humans. Most species of bacteria are harmless and are often beneficial but others can cause infectious diseases. The number of t ...
, especially
encapsulated bacterial infections, as well as a risk of
Systemic Lupus Erythematosus (SLE) or SLE-like disease.
Complement deficiency has historically been associated with early, severe bacterial infections among children.
Infection susceptibility is frequently observed.
C2D is linked to abnormalities in serum
immunoglobulin levels, such as lower
IgG2
Immunoglobulin G (Ig G) is a type of antibody. Representing approximately 75% of serum antibodies in humans, IgG is the most common type of antibody found in blood circulation. IgG molecules are created and released by plasma B cells. Each IgG ...
and
IgG4
Immunoglobulin G (Ig G) is a Antibody#Classes, type of antibody. Representing approximately 75% of blood plasma, serum immunoglobulins, antibodies in humans, IgG is the most common type of antibody found in Circulatory system, blood circulation. I ...
levels, which could contribute to raised infection susceptibility. More than half of 40 C2D patients in a study had
Streptococcus pneumoniae
''Streptococcus pneumoniae'', or pneumococcus, is a Gram-positive, spherical bacteria, alpha-hemolytic (under aerobic conditions) or beta-hemolytic (under anaerobic conditions), aerotolerant anaerobic member of the genus Streptococcus. They ar ...
-related invasive infection, primarily
meningitis or
septicemia
Sepsis, formerly known as septicemia (septicaemia in British English) or blood poisoning, is a life-threatening condition that arises when the body's response to infection causes injury to its own tissues and organs. This initial stage is follo ...
.
and
Neisseria meningitis are two other infections commonly seen in C2D patients.
Complications
In roughly 10% of patients, a C2 deficiency is linked to an illness that resembles
SLE.
Clinical manifestations of this SLE-like illness include
fever
Fever, also referred to as pyrexia, is defined as having a temperature above the normal range due to an increase in the body's temperature set point. There is not a single agreed-upon upper limit for normal temperature with sources using val ...
,
rash
A rash is a change of the human skin which affects its color, appearance, or texture.
A rash may be localized in one part of the body, or affect all the skin. Rashes may cause the skin to change color, itch, become warm, bumpy, chapped, dry, c ...
,
arthritis, and
glomerulonephritis
Glomerulonephritis (GN) is a term used to refer to several kidney diseases (usually affecting both kidneys). Many of the diseases are characterised by inflammation either of the glomeruli or of the small blood vessels in the kidneys, hence the ...
.
With a low titer,
ANA may be positive.
Anti-double-stranded DNA antibodies are uncommon.
Anti-Ro antibodies will be present in approximately 50% of the population.
associated with C2D is regarded as less severe when compared to other
complement deficiencies. In
SLE patients with C2D, skin and joint involvement are common, and severe persistent cutaneous and/or subacute
cutaneous lupus erythematosus can occur. Renal and neuropsychiatric disease, on the other hand, is thought to be uncommon in these SLE patients.
C2 deficiency has also been linked to
rheumatic diseases such as
membrane glomerulonephritis,
,
and
dermatomyositis
Dermatomyositis (DM) is a long-term inflammatory disorder which affects skin and the muscles. Its symptoms are generally a skin rash and worsening muscle weakness over time. These may occur suddenly or develop over months. Other symptoms may inc ...
.
Subacute
cutaneous lupus,
polymyositis
Polymyositis (PM) is a type of chronic inflammation of the muscles (inflammatory myopathy) related to dermatomyositis and inclusion body myositis. Its name means "inflammation of many muscles" ('' poly-'' + '' myos-'' + '' -itis''). The inflam ...
, and
Hodgkin's lymphoma
Hodgkin lymphoma (HL) is a type of lymphoma, in which cancer originates from a specific type of white blood cell called lymphocytes, where multinucleated Reed–Sternberg cells (RS cells) are present in the patient's lymph nodes. The condition w ...
have also been linked.
See also
*
Systemic Lupus Erythematosus
*
Complement deficiency
References
Further reading
*
External links
{{Lymphoid and complement immunodeficiency
Complement deficiency