Immunodeficiency 21

A number sign (#) is used with this entry because immunodeficiency-21 (IMD21) is caused by heterozygous mutation in the GATA2 gene (137295) on chromosome 3q21.

Primary lymphedema with myelodysplasia (614038), or Emberger syndrome, is an allelic disorder with overlapping clinical features.

Description

This primary immunodeficiency, designated IMD21, DCML, or MONOMAC, is characterized by profoundly decreased or absent monocytes, B lymphocytes, natural killer (NK) lymphocytes, and circulating and tissue dendritic cells (DCs), with little or no effect on T-cell numbers. Clinical features of IMD21 are variable and include susceptibility to disseminated nontuberculous mycobacterial infections, papillomavirus infections, opportunistic fungal infections, and pulmonary alveolar proteinosis. Bone marrow hypocellularity and dysplasia of myeloid, erythroid, and megakaryocytic lineages are present in most patients, as are karyotypic abnormalities, including monosomy 7 and trisomy 8. In the absence of cytogenetic abnormalities or overt dysplasia, hypoplastic bone marrow may initially be diagnosed as aplastic anemia. Bone marrow transplantation is the only cure. Some patients may have an increased risk of miscarriage. Both autosomal dominant transmission and sporadic cases occur. Less common manifestations of GATA2 deficiency include lymphedema and sensorineural hearing loss, a phenotype usually termed 'Emberger syndrome' (614038) (summary by Bigley et al. (2011), Hsu et al. (2011), and Spinner et al. (2014)).

Clinical Features

Biron et al. (1989) reported a 13-year-old girl who presented with disseminated varicella-zoster infection with varicella pneumonia. She had a history of recurrent otitis media from infancy. She later developed recurrent infections, particularly to viruses, including cytomegalovirus and herpes simplex virus. Laboratory studies showed persistent leukopenia, although antibody production and lymphoproliferative responses were normal. Detailed immunologic work-up revealed that she had no NK-cell function and lacked both NK cells and precursor NK cells. There was no family history of a similar disorder. The findings suggested that NK cells play a major defensive role against viral infections. In a follow-up, Mace et al. (2013) noted that the patient reported by Biron et al. (1989) subsequently developed aplastic anemia and died during hematopoietic stem cell transplantation.

Vinh et al. (2010) reported 6 male and 12 female patients from 13 white and 3 Hispanic kindreds with a clinical phenotype of susceptibility to disseminated nontuberculous mycobacterial infections, viral infections, especially with human papillomaviruses, and fungal infections, primarily histoplasmosis. The patients ranged in age from 7 to 60 years, with a median age of 32 years. The syndrome typically had its onset in adulthood, and 5 of the patients had died. A literature review identified at least 7 potentially related cases. Five kindreds including 7 of the 18 patients exhibited likely autosomal dominant transmission, and anecdotal evidence suggested autosomal dominant transmission in 3 other kindreds. Immunophenotyping revealed profound monocytopenia, B-cell deficiency without hypogammaglobulinemia, and NK-cell deficiency, but usually normal or near normal T-lymphocyte numbers. Tissue macrophage and plasma cell numbers were normal. Ten patients developed 1 or more malignancies, including myelodysplasia/leukemia in 9 patients. Five patients developed pulmonary alveolar proteinosis. Three patients had abnormal cytogenetics, including trisomy 8, monosomy 7, and dicentric chromosome 6.

Bigley et al. (2011) reported 4 additional patients with this immunodeficiency, which they called DCML. In addition to monocyte and B and NK lymphoid cell deficiency, they demonstrated a near absence of DCs in these patients, with preserved numbers of tissue macrophages and epidermal Langerhans cells. Multilymphoid progenitors were absent and granulocyte-macrophage progenitors were depleted in bone marrow. Serum FMS-like tyrosine kinase ligand (FLT3LG; 600007) was elevated, while circulating regulatory T cells were reduced. Bigley et al. (2011) concluded that DC deficiency is an integral part of the syndrome of autosomal and sporadic monocytopenia reported by Vinh et al. (2010).

Spinner et al. (2014) retrospectively reviewed the clinical features of 57 patients with GATA2 mutations. Forty patients were identified through clinical presentation and 17 through family screening. The most common manifestations were severe viral or nontuberculous mycobacterial infections and myelodysplasia/acute myeloid leukemia. Less common features included invasive fungal infections (16%), pulmonary alveolar proteinosis (18%), and lymphedema (11%). The age at onset was extremely variable (range, 5 months to 78 years), and 4 (7%) of the mutation carriers were asymptomatic at last follow-up. Hemograms and lymphocyte phenotyping for 55 and 51 patients, respectively, showed B lymphocytopenia (86%), NK lymphocytopenia (82%), monocytopenia (78%), CD4 lymphocytopenia (51%), and neutropenia (47%). Forty-two (84%) of 50 patients who underwent bone marrow biopsy showed myelodysplastic syndrome. Nineteen (76%) of 25 patients who underwent audiograms showed mild to severe sensorineural hearing loss, which may have been complicated by antibiotic use. Dermatologic disease was often an indicator of chronic viral infection or malignancy. Fourteen (33%) of 43 known pregnancies resulted in miscarriage, and 14% of patients developed hypothyroidism. There were no obvious genotype/phenotype correlations, although severe viral infections were more common and showed earlier onset in those with null mutations, and lymphedema was only observed in those with null or regulatory domain mutations.

Inheritance

The transmission pattern of IMD21 in at least half of the families reported by Vinh et al. (2010) was consistent with autosomal dominant inheritance.

Clinical Management

Cuellar-Rodriguez et al. (2011) performed nonmyeloablative hematopoietic stem cell transplant in 6 patients with GATA2 deficiency. Two patients received peripheral blood stem cells (PBSCs) from matched related donors; 2 received PBSCs from matched unrelated donors; and 2 received stem cells from umbilical cord blood (UCB) donors. Recipients of matched related and unrelated donors received fludarabine and 200 cGy of total body irradiation (TBI), while UCB recipients received cyclophosphamide in addition to fludarabine and TBI as conditioning. All patients received tacrolimus and sirolimus posttransplantation. Five patients were alive at a median follow-up of 17.4 months (range, 10-25). All patients achieved high levels of donor engraftment in the hematopoietic compartments that were deficient pretransplantation. Adverse events consisted of delayed engraftment in the recipient of a single UCB transplant, graft-versus-host disease in 4 patients, and immune-mediated pancytopenia and nephrotic syndrome in the recipient of a double UCB transplant. Cuellar-Rodriguez et al. (2011) concluded that nonmyeloablative hematopoietic stem cell transplant in GATA2 deficiency results in reconstitution of the severely deficient monocyte, B-cell, and NK-cell populations and in reversal of the clinical phenotype.

Molecular Genetics

Hsu et al. (2011) identified 12 distinct heterozygous mutations in the GATA2 gene in 20 patients with DCML, which they termed MONOMAC due to monocyte deficiency and susceptibility to mycobacteria, typically M. avium complex (MAC). The mutations were identified in 12 patients from 10 of the 16 kindreds originally reported by Vinh et al. (2010) and in 8 patients from 8 different kindreds not previously reported. In 2 kindreds, the mutation identified in the proband was identified in an affected relative, confirming germline transmission. Of the remaining 6 kindreds reported by Vinh et al. (2010), mutations in GATA2 were not identified in 3, and 3 were not analyzed. Five of the 6 missense mutations, including 2 recurrent mutations, arg398 to trp (R398W; 137295.0001) and thr354 to met (T354M; 137295.0002), affected the zinc finger-2 domain in GATA2, suggesting dominant interference of protein function. The remaining missense mutation, pro254 to leu (P254L; 137295.0003), occurred before the zinc fingers and was predicted to be damaging. Six patients had insertion/deletion mutations, 4 of which (e.g., 137295.0004) led to frameshifts and premature termination and implicated haploinsufficiency. Hsu et al. (2011) concluded that GATA2, like RUNX1 (151385) and CEBPA (116897), is involved in familial leukemia and in a complex congenital immunodeficiency that evolves over decades and leads to predisposition to infection and myeloid malignancy.

By exome sequence analysis of 4 unrelated patients with DCML previously reported by Bigley et al. (2011), including 3 with sporadic DCML, Dickinson et al. (2011) found that only mutations in GATA2 were shared by all 4 patients. Each patient harbored a unique mutation, but all were predicted to be deleterious. The mutations included 2 missense mutations within the zinc finger domain, R398W and T354M, a 1-bp insertion in codon 200 (137295.0007) predicted to cause a frameshift and premature termination, and a splice acceptor site mutation (137295.0008) predicted to cause skipping of exon 5 and a 42-amino acid deletion. The frameshift and splice acceptor mutations were expected to result in complete loss of the C-terminal zinc finger domain and to cause DCML through haploinsufficiency of GATA2.

Johnson et al. (2012) identified a woman of European descent who developed a constellation of conditions characteristic of MONOMAC by the age of 27 years. The patient lacked mutations in her GATA2 cDNA, and 3 conserved GATA regulatory sites upstream of the GATA2 promoter were identical to wildtype. However, Johnson et al. (2012) identified a 28-bp deletion in intron 5 at +9.5 kb (137295.0015) that affected a conserved composite E-box/GATA element. The deletion excised an imperfect GATA motif (GATAG), the E-box of the conserved composite element (CATCTG), and 5 bp of the 8-bp spacer between the E-box and the GATA motif (AGATAA). Johnson et al. (2012) suggested that heterozygous mutation of the +9.5 site reduces GATA2 expression in vivo.

In a girl with primary immunodeficiency originally reported by Biron et al. (1989), Mace et al. (2013) identified a heterozygous mutation in the GATA2 gene (137295.0016).

Pathogenesis

Mace et al. (2013) found that the NK cells of 5 patients with immunodeficiency due to GATA2 mutations showed a profound defect in NK cell-mediated cytotoxicity, as well as a defect in antibody-mediated cellular toxicity. There was a severe reduction in CD56 (NCAM1; 116930)-bright cells, which represent the precursor NK-cell pool, and the remaining NK cells were CD56-dim, representing the mature pool. Analysis of control NK cells showed that GATA2 was expressed primarily in the CD56-bright pool, suggesting an important role for GATA2 in the differentiation, maturation, and survival of NK cells.