Acute lymphoblastic leukemia (ALL), also known as acute lymphocytic leukemia, is a subtype of acute leukemia, a cancer of the white blood cells. Somatically acquired mutations in several genes have been identified in ALL lymphoblasts, cells in the early stages of differentiation. Germline variation in certain genes may also predispose to susceptibility to ALL (Trevino et al., 2009). Genetic Heterogeneity of Acute Lymphoblastic Leukemia A susceptibility locus for acute lymphoblastic leukemia (ALL1) has been mapped to chromosome 10q21. See also ALL2 (613067), which has been mapped to chromosome 7p12.2; and ALL3 (615545), which is caused by mutation in the PAX5 gene (167414) on chromosome 9p.

The phenotypic spectrum of ataxia-telangiectasia (A-T), a multisystem disorder, is a continuum ranging from classic A-T at the severe end and variant A-T at the milder end. Nonetheless, distinguishing between classic A-T and variant A-T on this spectrum helps understand differences in disease course, rate of progression, and life expectancy. Classic A-T is characterized by childhood onset of progressive neurologic manifestations (initially cerebellar ataxia, followed typically by extrapyramidal involvement and peripheral sensorimotor neuropathy), immunodeficiency (variably associated with abnormalities of humoral immunity, cellular immunity, or combined immune deficiency), pulmonary disease (resulting from recurrent infections, immune deficiency, aspiration, interstitial lung disease, and neurologic abnormalities), and increased risk of malignancy. Although it is generally accepted that intellectual disability is not common in A-T, disturbances in cerebellar as well as non-cerebellar brain areas and networks may result in cognitive deficits. Increased sensitivity to ionizing radiation (x-ray and gamma ray) can result in severe side effects from such treatments. Life expectancy is significantly reduced due to cancer, pulmonary disease, and infections. Variant A-T has a significantly milder disease course. While cerebellar ataxia can be absent, extrapyramidal movement disorders are common (typically dystonia and dystonic tremor) and most individuals have manifestations of axonal sensorimotor polyneuropathy. In contrast to classic A-T, immune function is generally normal, respiratory infections are not increased, and pulmonary disease is not a major feature. However, risk of developing malignancies is increased, particularly in premenopausal females who have an increased risk of developing breast cancer and hematologic malignancies.

Acute lymphoblastic leukemia (ALL), also known as acute lymphocytic leukemia, is a subtype of acute leukemia, a cancer of the white blood cells. Somatically acquired mutations in several genes have been identified in ALL lymphoblasts, cells in the early stages of differentiation. Germline variation in certain genes may also predispose to susceptibility to ALL (Trevino et al., 2009). Genetic Heterogeneity of Acute Lymphoblastic Leukemia A susceptibility locus for acute lymphoblastic leukemia (ALL1) has been mapped to chromosome 10q21. See also ALL2 (613067), which has been mapped to chromosome 7p12.2; and ALL3 (615545), which is caused by mutation in the PAX5 gene (167414) on chromosome 9p.

Dubowitz syndrome (DS) is a rare multiple congenital syndrome characterized primarly by growth retardation, microcephaly, distinctive facial dysmorphism, cutaneous eczema, a mild to severe intellectual deficit and genital abnormalities.

LIG4 syndrome is an autosomal recessive severe combined immunodeficiency with features of radiosensitivity, chromosomal instability, pancytopenia, and developmental and growth delay. Leukemia and dysmorphic facial features have been reported in some patients (summary by van der Burg et al., 2006).

CHIME syndrome, also known as Zunich neuroectodermal syndrome, is an extremely rare autosomal recessive multisystem disorder clinically characterized by colobomas, congenital heart defects, migratory ichthyosiform dermatosis, mental retardation, and ear anomalies (CHIME). Other clinical features include distinctive facial features, abnormal growth, genitourinary abnormalities, seizures, and feeding difficulties (summary by Ng et al., 2012). The disorder is caused by a defect in glycosylphosphatidylinositol (GPI) biosynthesis. For a discussion of genetic heterogeneity of GPI biosynthesis defects, see GPIBD1 (610293).

Noonan syndrome (NS) is characterized by characteristic facies, short stature, congenital heart defect, and developmental delay of variable degree. Other findings can include broad or webbed neck, unusual chest shape with superior pectus carinatum and inferior pectus excavatum, cryptorchidism, varied coagulation defects, lymphatic dysplasias, and ocular abnormalities. Although birth length is usually normal, final adult height approaches the lower limit of normal. Congenital heart disease occurs in 50%-80% of individuals. Pulmonary valve stenosis, often with dysplasia, is the most common heart defect and is found in 20%-50% of individuals. Hypertrophic cardiomyopathy, found in 20%-30% of individuals, may be present at birth or develop in infancy or childhood. Other structural defects include atrial and ventricular septal defects, branch pulmonary artery stenosis, and tetralogy of Fallot. Up to one fourth of affected individuals have mild intellectual disability, and language impairments in general are more common in NS than in the general population.

Common variable immunodeficiency-13 (CVID13) is an autosomal dominant primary immunodeficiency disorder characterized by recurrent bacterial infections, mainly affecting the respiratory tract, and associated with hypogammaglobulinemia and decreased numbers of B cells. The age at onset of clinical features can range from infancy to adulthood, and some patients may have a mild disorder or even remain clinically asymptomatic (summary by Kuehn et al., 2016). For a general description and a discussion of genetic heterogeneity of common variable immunodeficiency, see CVID1 (607594).

Severe congenital neutropenia-3 is an autosomal recessive bone marrow failure disorder characterized by low numbers of neutrophils, increased susceptibility to bacterial and fungal infections, and increased risk of developing myelodysplastic syndrome or acute myeloid leukemia. In addition, patients with HAX1 mutations affecting both isoform A and B of the gene develop neurologic abnormalities (summary by Boztug et al., 2010). The Swedish physician Rolf Kostmann (1956) described an autosomal recessive hematologic disorder, termed infantile agranulocytosis, with severe neutropenia with an absolute neutrophil count below 0.5 x 10(9)/l and early onset of severe bacterial infections. The disorder was later termed Kostmann syndrome (Skokowa et al., 2007). Lekstrom-Himes and Gallin (2000) discussed severe congenital neutropenia in a review of immunodeficiencies caused by defects in phagocytes. In addition to Kostmann agranulocytosis, recessively inherited neutropenic syndromes include congenital neutropenia with eosinophilia (257100), Chediak-Higashi syndrome (214500), and Fanconi pancytopenic syndrome (see 227650). For a phenotypic description and a discussion of genetic heterogeneity of severe congenital neutropenia, see SCN1 (202700).