Severe congenital neutropenia | |
---|---|
Other names | Kostmann disease, Kostmann's agranulocytosis, Kostmann's syndrome, congenital agranulocytosis, congenital neutropenia, permanent neutropenia, infantile genetic agranulocytosis, severe infantile genetic neutropenia |
Specialty | Hematology |
Usual onset | Infancy [1] |
Types | SCN1-SCN5, SCNX |
Causes | Mutation in genes, depending on type [1] |
Diagnostic method | Blood test, genetic testing [1] |
Treatment | G-CSF, HSCT [1] |
Medication | Filgrastim [1] |
Frequency | 2-3 in million (2018) [1] |
Severe congenital neutropenia (SCN), also often known as Kostmann syndrome or disease, is a group of rare disorders that affect myelopoiesis, causing a congenital form of neutropenia, usually without other physical malformations. SCN manifests in infancy with life-threatening bacterial infections. [2] It causes severe pyogenic infections. It can be caused by autosomal dominant inheritance of the ELANE gene, autosomal recessive inheritance of the HAX1 gene. There is an increased risk of leukemia and myelodysplastic cancers.
Most cases of SCN respond to treatment with granulocyte colony-stimulating factor (filgrastim), which increases the neutrophil count and decreases the severity and frequency of infections. [2] Although this treatment has significantly improved survival, people with SCN are at risk of long-term complications such as hematopoietic clonal disorders (myelodysplastic syndrome, acute myeloid leukemia).
Kostmann disease (SCN3), the initial subtype recognized, was clinically described in 1956. This type has an autosomal recessive inheritance pattern, whereas the most common subtype, SCN1, shows autosomal dominant inheritance.[ citation needed ]
Infants with SCN have frequent infections: 50% have a significant infection within one month, most others by six months. [3] Their etiology is usually bacterial, especially staphylococcal, and they commonly involve abscesses, both cutaneous and of internal organs, pneumonia, mastoiditis (inflammation of the mastoid process), and sepsis. All of these are life-threatening for infants. [4]
OMIM | Name | Gene | Chromosome | Gene/Locus MIM number |
---|---|---|---|---|
202700 | SCN1 | ELANE | 19p13.3 | 130130 [5] |
613107 | SCN2 | GFI1 | 1p22.1 | |
610738 | SCN3 | HAX1 | 1q21.3 | |
612541 | SCN4 | G6PC3 | 17q21.31 | |
615285 | SCN5 | VPS45 | 1q21.2 | |
300299 | SCNX | WASP | Xp11.23 | 300392 [6] |
Kostmann disease, SCN3, is inherited in an autosomal recessive manner, but the commonest subtype of Kostmann syndrome, SCN1, is autosomal dominant. [7]
A significant proportion of SCN lacks a known mutation. [8] The recognized subtypes of Kostmann syndrome are:
SCN occasionally may arise from SBDS mutations. [8]
Severe congenital neutropenia (SCN) is used as the overarching term for all diseases that affect myelopoiesis most prominently. Kostmann syndrome can restrictively refer to Kostmann disease specifically, or can be used synonymously with SCN as an umbrella term. These syndrome subtypes are phenotypically similar despite arising from different gene abnormalities. [3]
Kostmann disease is a form of severe congenital neutropenia (SCN), specifically type 3 (SCN3), [15] which is a rare autosomal recessive condition in which severe chronic neutropenia is detected soon after birth. [7] [16] The disorder was discovered in 1956 in an extended family in northern Sweden by Rolf Kostmann, a Swedish doctor. [17] [18]
Although mutations of more than 15 genes cause severe congenital neutropenia (in a general sense) [19] not all of these are usually considered as SCN. Clinical usage excludes two broad categories of congenital neutropenia. Diseases are excluded that overtly affect multiple systems rather than impacting myelopoiesis most prominently. Thus SCN excludes the severe neutropenia which can occur in congenital diseases such as Shwachman–Diamond syndrome, Barth syndrome, Chédiak–Higashi syndrome, WHIM syndrome, and glycogen storage disease type Ib. [19] A further group of other miscellaneous inherited disorders, such as hyper IgM syndrome, Hermansky–Pudlak syndrome (HPS), Griscelli syndrome (GS), PN, P14 deficiency, Cohen syndrome, Charcot–Marie–Tooth disease (CMT) can show congenital neutropenia, but lack bone marrow findings typical of SCN.[ citation needed ]
This group of diseases may also have additional features such as partial albinism, retinopathy, or neuropathy, and are not inclined to degenerate into acute myelogenous leukemia. [3]
GATA2 deficiency is a grouping of several disorders caused by common defect, viz., familial or sporadic inactivating mutations in one of the two parental GATA2 genes. These autosomal dominant mutations cause a reduction, i.e. a haploinsufficiency, in the cellular levels of the gene's product, GATA2. The GATA2 protein is a transcription factor critical for the embryonic development, maintenance, and functionality of blood-forming, lympathic-forming, and other tissue-forming stem cells. In consequence of these mutations, cellular levels of GATA2 are deficient and individuals develop over time hematological, immunological, lymphatic, or other presentations that may begin as apparently benign abnormalities but commonly progress to a more serious disorder. A small but significant percentage of individuals with GATA2 deficiency's present with congenital neutropenia. This neutropenia is typically mild, often persists for years, and therefore is not a Kostmann syndrome disorder. Over time, however, the deficiency commonly progresses to include thrombocytopenia, increases susceptibility to infections due to, e.g. atypical mycobacteria or human papillomavirus, dysfunction of non-hematological organs, the myelodysplastic syndrome, and/or a leukemia, particularly acute myelogenous leukemia. [20] [21] [22]
The various mutations are responsible for the untimely initiation of apoptosis in myelocytes, usually at the promyelocyte stage, leading to their premature destruction or maturation arrest in the bone marrow. [23] The ineffective production of neutrophils leads to a decrease in the absolute neutrophil count and a subsequent increased susceptibility to infections. There may be, in addition, other underlying molecular/genetic changes producing DNA mutations and genome instability, which contribute to initiation and progression of this disease.[ citation needed ]
A diagnosis can be made as early as a few days after birth. Observable symptoms may include difficulty breathing, infections that occurred in the womb, and issues that arise in the weeks following birth, such as abscesses along with gingivitis and periodontitis. [24] An absolute neutrophil count (ANC) chronically less than 500/mm3, usually less than 200/mm3, is the main sign of Kostmann's. Other elements include the severity of neutropenia, the chronology (from birth; not emerging later), and other normal findings (hemoglobin, platelets, general body health). Isolated neutropenia in infants can occur in viral infections, autoimmune neutropenia of infancy, bone marrow suppression from a drug or toxin, hypersplenism, and passive placental transfer of maternal IgG. [3]
A bone marrow test can assist in diagnosis. The bone marrow usually shows early granulocyte precursors, but myelopoietic development stops ("arrests") at the promyelocyte and/or myelocyte stage, so that few maturing forms are seen. Neutrophil survival is normal.[ citation needed ]
Regular administration of exogenous granulocyte colony-stimulating factor (filgrastim) clinically improves neutrophil counts and immune function and is the mainstay of therapy, although this may increase risk for myelofibrosis and acute myeloid leukemia in the long term. [25]
Over 90% of SCN responds to treatment with granulocyte colony-stimulating factor (filgrastim), which has significantly improved survival.[ citation needed ]
A myelodysplastic syndrome (MDS) is one of a group of cancers in which immature blood cells in the bone marrow do not mature, and as a result, do not develop into healthy blood cells. Early on, no symptoms typically are seen. Later, symptoms may include fatigue, shortness of breath, bleeding disorders, anemia, or frequent infections. Some types may develop into acute myeloid leukemia.
Neutropenia is an abnormally low concentration of neutrophils in the blood. Neutrophils make up the majority of circulating white blood cells and serve as the primary defense against infections by destroying bacteria, bacterial fragments and immunoglobulin-bound viruses in the blood. People with neutropenia are more susceptible to bacterial infections and, without prompt medical attention, the condition may become life-threatening.
In molecular biology, elastase is an enzyme from the class of proteases (peptidases) that break down proteins. In particular, it is a serine protease.
Immunodeficiency, also known as immunocompromisation, is a state in which the immune system's ability to fight infectious diseases and cancer is compromised or entirely absent. Most cases are acquired ("secondary") due to extrinsic factors that affect the patient's immune system. Examples of these extrinsic factors include HIV infection and environmental factors, such as nutrition. Immunocompromisation may also be due to genetic diseases/flaws such as SCID.
Myelokathexis is a congenital disorder of the white blood cells that causes severe, chronic leukopenia and neutropenia. The disorder is believed to be inherited in an autosomal dominant manner. Myelokathexis refers to retention (kathexis) of neutrophils in the bone marrow (myelo). The disorder shows prominent neutrophil morphologic abnormalities.
Cyclic neutropenia (CyN) is a rare hematologic disorder and form of congenital neutropenia that tends to occur approximately every three weeks and lasting for few days at a time due to changing rates of neutrophil production by the bone marrow. It causes a temporary condition with a low absolute neutrophil count and because the neutrophils make up the majority of circulating white blood cells it places the body at severe risk of inflammation and infection. In comparison to severe congenital neutropenia, it responds well to treatment with granulocyte colony-stimulating factor (filgrastim), which increases the neutrophil count, shortens the cycle length, as well decreases the severity and frequency of infections.
Nijmegen breakage syndrome (NBS) is a rare autosomal recessive congenital disorder causing chromosomal instability, probably as a result of a defect in the double Holliday junction DNA repair mechanism and/or the synthesis dependent strand annealing mechanism for repairing double strand breaks in DNA.
GATA-binding factor 1 or GATA-1 is the founding member of the GATA family of transcription factors. This protein is widely expressed throughout vertebrate species. In humans and mice, it is encoded by the GATA1 and Gata1 genes, respectively. These genes are located on the X chromosome in both species.
Neutrophil elastase is a serine proteinase in the same family as chymotrypsin and has broad substrate specificity. Neutrophil elastase is secreted by neutrophils during inflammation, and destroys bacteria and host tissue. It also localizes to neutrophil extracellular traps (NETs), via its high affinity for DNA, an unusual property for serine proteases.
Purine nucleoside phosphorylase deficiency is a rare autosomal recessive metabolic disorder which results in immunodeficiency.
Congenital hypoplastic anemia is a congenital disorder that occasionally also includes leukopenia and thrombocytopenia and is characterized by deficiencies of red cell precursors.
Shwachman–Diamond syndrome (SDS), or Shwachman–Bodian–Diamond syndrome, is a rare congenital disorder characterized by exocrine pancreatic insufficiency, bone marrow dysfunction, skeletal and cardiac abnormalities and short stature. After cystic fibrosis (CF), it is the second most common cause of exocrine pancreatic insufficiency in children. It is associated with the SBDS gene and has autosomal recessive inheritance.
Glucose-6-phosphatase 3, also known as glucose-6-phosphatase beta, is an enzyme that in humans is encoded by the G6PC3 gene.
MonoMAC syndrome is a rare autosomal dominant syndrome associated with: monocytopenia, B and NK cell lymphopenia; mycobacterial, viral, fungal, and bacterial opportunistic infections; and virus infection-induced cancers. The disorder often progresses to the development of myelodysplasia, myeloid leukemias, and other types of cancer. MonoMAC is a life-threatening and precancerous disorder.
Reticular dysgenesis (RD) is a rare, inherited autosomal recessive disease that results in immunodeficiency. Individuals with RD have mutations in both copies of the AK2 gene. Mutations in this gene lead to absence of AK2 protein. AK2 protein allows hematopoietic stem cells to differentiate and proliferate. Hematopoietic stem cells give rise to blood cells.
Neutrophil-specific granule deficiency is a rare congenital immunodeficiency characterized by an increased risk for pyogenic infections due to defective production of specific granules and gelatinase granules in patient neutrophils.
Kenny-Caffey syndrome type 2 (KCS2) is an extremely rare autosomal dominant genetic condition characterized by dwarfism, hypermetropia, microphthalmia, and skeletal abnormalities. This subtype of Kenny-Caffey syndrome is caused by a heterozygous mutation in the FAM111A gene (615292) on chromosome 11q12.
GATA2 deficiency is a grouping of several disorders caused by common defect, namely, familial or sporadic inactivating mutations in one of the two parental GATA2 genes. Being the gene haploinsufficient, mutations that cause a reduction in the cellular levels of the gene's product, GATA2, are autosomal dominant. The GATA2 protein is a transcription factor critical for the embryonic development, maintenance, and functionality of blood-forming, lymphatic-forming, and other tissue-forming stem cells. In consequence of these mutations, cellular levels of GATA2 are deficient and individuals develop over time hematological, immunological, lymphatic, or other presentations that may begin as apparently benign abnormalities but commonly progress to severe organ failure, opportunistic infections, virus infection-induced cancers, the myelodysplastic syndrome, and/or leukemia. GATA2 deficiency is a life-threatening and precancerous condition.
P14 deficiency is a rare autosomal recessive disease characterized as a primary immunodeficiency syndrome. This disease was first identified within a white Mennonite family by Professor Bodo Grimbacher and Professor Christoph Klein’s teams in 2006. Four out of 15 offspring in this family showed symptoms including short stature, recurrent infection of Streptococcus pneumonia, and dysfunction of cells that contain specific lysosome-related organelles, including cytotoxic T cells, melanocytes, and neutrophil granulocytes.