Large Granular Lymphocyte Infiltration in the Bone Marrow in Children and Young Adults May Suggest Primary Immune Deficiency

Large granular lymphocyte (LGL) leukemia is a group of rare lymphoproliferative disorders which involve inappropriate clonal expansion of either cytotoxic T-lymphocytes (CTLs) or natural killer cells (NK). The usual age at onset is between 40 to 60 years. We here describe four very young patients showing LGL infiltration in the bone marrow (BM) and all diagnosed with primary immune deficiency.

Patient 1 is a 13-year old male who presented with gingivostomatitis, but no severe infections, autoimmune disease or allergies. He had persistent leukopenia (1.9x10⁹/L), neutropenia (<0.05x10⁹/L), thrombocytopenia (60-80x10⁹/L) and mild anemia. The BM showed myeloid maturation arrest and infiltration of LGL cells with NK cell phenotype (CD3-, CD2+, CD16+, CD56-/+, CD57-, CD4-, CD8-) at 50% of the BM cellularity. In peripheral blood (PB) T, B and NK cell counts were normal. However, low levels of monocytes (0.09x10⁹/L), normal levels of monocytoid (2.7x10⁶/L) and low levels of plasmacytoid (0.1x10⁶/L) dendritic cells (DC) were detected. While germline whole exome sequencing (WES) did not identify mutations likely to cause the disease, targeted sequencing of GATA2 mRNA showed uniallelic GATA2 expression, confirming haploinsufficiency.

Patient 2 is a 15-year old female who has neonatal diabetes, autoimmune desquamative interstitial pulmonary disease, autoimmune enteropathy, exocrine pancreatic insufficiency and delayed growth. She developed transfusion-dependent, Coombs-negative anemia at age of 15. In the PB, 50% of the lymphocytes were LGLs. BM showed pure red cell aplasia plus LGL infiltration of TCRgd positive T cells (CD3+, CD2+, CD5+,CD8-/+,CD4-/+, CD57+) at 43% of BM cellularity. Clonal TCRg rearrangement was detected.  Hypogammaglobulinemia presented at age of 7. T, B and NK cell counts were low normal, but DCs were non-existent. WES and functional studies revealed a germline gain-of-function mutation of STAT3 gene.

Patient 3 is 42-year old female who has had severe infections (bacterial, viral and protozoan) starting at the age of 4 months. From age of 9, autoimmune manifestations occurred with immune thrombocytopenia, neutropenia and anemia, and intensively positive rheumatoid factor. Since age of 17, CD8+ LGLs were detected in PB reaching level of 50% of lymphocytes. In the BM, CD3+CD5-CD56- T -lymphocyte infiltration with clonal TCRd rearrangement was detected. In her 30ies she developed pulmonal arterial hypertension and hypogammaglobulinemia (0.8 g/L). She has low counts of B cells (0.02x109/L), and monocytoid (1.9x10⁶/L) and plasmacytoid (0) DCs. WES identified a homozygous germline missense mutation in CECR1 gene, leading to total loss-of-function of the encoded adenosine deaminase 2 (ADA2) protein.

Patient 4 presented with waxing and waning skin nodules from age of 10 years, but no severe infections or allergies. At age of 26, she was diagnosed with hemolytic anemia with spherocytosis, splenomegaly and cholelithiasis. Five years later remarkable hepatomegaly, and clinical autoimmune manifestations with SLE-type skin lesions, autoimmune hemolytic anemia and iritis were observed. Complement C3 (0.17 g/l) and C4 (<0.02 g/L) and NK cell (0.081) levels were low, but CD3, CD8 and CD4 counts and IgM and IgG levels were increased. T-cell infiltration was shown in the skin nodules and liver. BM showed mildly decreased myelo- and erythropoiesis and  T cell infiltration (CD3+, CD8+,CD7+, CD45RO+, BCL2+,CD56-) up to 70% of the BM cellularity consistent with LGL infiltration. WES identified the same germline missense mutation in CECR1 gene as seen in patient 3, and a functional analysis showed no ADA2 activity.

We conclude that LGL lymphoproliferation in young patients is often a sign of underlying primary immunodeficiency, highlighting the need for detailed genetic studies in these cases.

Patient	Age at LGL	LGL in PB (109/L)	LGL immune-phenotype	Clonality	BM LGL infiltration	Clinical	PID
1	13	0.38	NK	NA	40%	N,T Hepatomegaly	GATA2 deficiency
2	15	1.79	CTL	TCRg	43%	Autoimmunity A Hepatosplenomegaly	STAT3 hyperactivation
3	17	1,49	CTL	TCRd	NA	N,T, A Autoimmunity Pulmonary arterial hypertension	ADA2 deficiency
4	31	NA	CTL	TCRg weak	40%	Autoimmunity Hepatosplenomegaly Hepatopulmonal syndrome	ADA2 deficiency

A, anemia; N, neutropenia, CTL, cytotoxic T cell; LGL, large granular lymphocyte; NK, natural killer cell; PID, primary immune deficiency; TCR, T cell receptor; T, thrombocytopenia