Keywords
transient abnormal myelopoiesis - Down syndrome -
GATA1 mutation - hyperleukocytosis
Introduction
Children with Down syndrome (DS) have an increased chance of developing acute leukemia.
Acute myeloid leukemia and acute lymphoblastic leukemia risks are increased by 150
and ~30-fold, respectively, in children with DS.[1]
[2] Transient abnormal myelopoiesis (TAM) is characterized by increased circulating
blast cells (>10%) and GATA1 mutation with or without clinical features and requires close monitoring.[3]
[4] A few neonates with DS may have small mutant clones of GATA1 along with <10% of blasts and these patients have clinically and hematologically
silent disease (silent TAM).[5] In a majority of cases of TAM, complete remission with reversal of GATA1 mutant clone occurs spontaneously without the requirement of chemotherapy. Nevertheless,
10 to 20% of neonates with TAM consequently develop myeloid leukemia of DS in the
first 5 years of life.[6] The reported mortality rate of TAM is up to 20%.[7] Here we describe a case of TAM with novel GATA1 mutation who subsequently required chemotherapy and recovered.
Case Report
Case History
A 2-month-old male infant, second child born out of a nonconsanguineous marriage to
a 22-year-old second gravida mother at term gestation, delivered at home with a birth
weight of 2 kg, cried immediately after birth, and had no perinatal complications.
The baby was well for the initial 10 days of life, after which he developed cough,
coryza, and poor feeding for 5 days with bluish discoloration of lips while crying,
inadequate weight gain, forehead sweating, and suck-rest-suck cycle. There was no
puffiness of eyes, abdominal distension, progressive pallor, or bleeding manifestations.
The child was admitted to a nearby hospital in the third week of life for these complaints.
He underwent echocardiography and was diagnosed to have cyanotic congenital heart
disease. He was referred to our hospital for cardiac surgery and further management
in the sixth week of life. In preoperative workup at the cardiology unit, the child
was found to have a high total leukocyte count (TLC) of 1,29,000 × mm3 and transferred to us for further workup in the eighth week of life.
Clinical Findings
On examination, the child's heart rate was 165/min, respiratory rate was 53/min, and
blood pressure was normal with no difference in the four limbs with oxygen saturation
of 60 to 63% in all extremities. The infant's weight was 2.2 kg, length was 47 cm,
and head circumference was 33 cm, suggestive of failure to thrive. He had central
cyanosis, wide-open anterior fontanelle (3 cm × 3 cm), with open posterior fontanelle.
The baby had a Down phenotype with flat facies, epicanthal eye fold, low set ears,
mongoloid slant, clinodactyly, generalized hypotonia, and sandal gap. On cardiovascular
examination, the apical impulse was felt in the left 4th intercostal space in the
midclavicular line, with a short systolic murmur well heard in the left lower sternal
border. The liver was palpable 6 cm below the right costal margin and the spleen palpable
3 cm along the splenic axis. The child had tachypnea with mild subcostal and intercostal
retractions with normal auscultatory findings, and central nervous examination was
within normal limits.
Diagnostic Assessment
Initial complete blood counts revealed hemoglobin of 14 g/dL, TLC of 129,000/ mm3, platelet count of 2,20,000/ mm3, blood urea of 52 mg/dL, serum creatinine of 0.6 mg/dL, uric acid of 6.6 mg/dL, sodium
of 135 mEq/L, potassium of 4.7 mEq/L, total protein of 5.2 g/dL, albumin of 3.8 g/dL,
total bilirubin of 0.9 mg/dL, aspartate transaminase of 31 IU/L, alanine transaminase
of 26 IU/L, alkaline phosphatase of 374 IU/L, total calcium of 8.7 mg/dL, and phosphorus
of 5.6 mg/dL. His serum thyroid stimulating hormone was high (8.89 mIU/L); T3 (0.57
ng/mL) and T4 level (4.15 µg/dL) were normal. Chest X-ray showed no cardiomegaly,
pericardial, or pleural effusion. Echocardiography revealed d-transposition of great
arteries with 7 mm ostium secundum atrial septal defect and 2 mm patent ductus arteriosus
with moderate pulmonary artery hypertension.
His karyotyping was suggestive of trisomy 21. Peripheral smear examination revealed
74% blasts ([Fig. 1]), and bone marrow examination revealed 25% myeloid series blasts. Megakaryocytes
appeared reduced, and blasts were negative for myeloperoxidase (MPO) staining. Bone
marrow flow cytometry revealed 25% CD45 dim+ blasts that were CD34+ (heterogeneous),
CD33+ (heterogeneous), CD117+ (heterogeneous), CD38+, HLA-DR+ (heterogeneous), CD56
(heterogeneous), CD7 (heterogeneous), CD36+, CD4+(dim) and negative for cMPO, cCD79a,
CD13, CD19, cCD3, sCD3, CD16, CD123, CD11b, CD64, and CD14. A subset of 30% blasts
also express CD34+ (heterogeneous), CD117+ (heterogeneous), cCD41+, cCD61+, CD36 +,
CD23a+, and CD71 (dim heterogeneous). Next-generation sequencing (NGS) from the bone
marrow aspirate was detected to have novel GATA1 mutation showing a splice variant intron 2 mutation c.220+1 G>T (ENST00000376670.3)
([Fig. 2]). This mutation has not been reported in available genomic databases, which may
be a novel mutation in TAM.
Fig. 1 (A) Giemsa stain of peripheral smear showing blasts having high nuclear-cytoplasmic
ratio with cytoplasmic blebs; (B) myeloperoxidase (MPO) stains of peripheral smear showing blasts that are negative
for MPO along with neutrophil as control.
Fig. 2 (Integrative gemomics viewer) snapshot showing intron 2 mutation of the GATA genes.
(The nucleotide “G” is altered to “T” allele, leading to a splice variant in the GATA1
gene. The mutant allele percentage is 77% that means out of 796 reads, the T allele
is present in 77% of those reads. The annotation of the variant is c.220+1G>T.)
Therapeutic Intervention
The child was managed with diuretics and other anticongestive measures with oxygen
support for congestive cardiac failure. The child received allopurinol, thyroxine
supplementation, and platelet transfusion (for a platelet count of 10,000/ mm3). In view of hyperleukocytosis and hepatosplenomegaly leading to respiratory compromise,
cytarabine was given at 1 mg/kg twice a day for 7 days. The child went into remission
at 3 weeks, and blasts disappeared. After a stay of 4 weeks, the child was discharged
in a stable condition.
Follow-Up and Outcome
The child is active and doing fine 12 months since the diagnosis of TAM. His latest
hemoglobin was 10.9 g/dL, TLC was 13,450/ mm3, and platelet count was 1,50,000 × 10 mm3.
Discussion
TAM is a unique entity in DS and is also known as a transient myeloproliferative disorder
or transient leukemia of DS. It is a genetic diagnosis characterized by an increased
peripheral blood blast count in children with trisomy 21 or mosaic DS with GATA1 mutation with or without clinical features of TAM.[7]
GATA1 mutation and DS are a prerequisite to label as TAM.
There is no defined blast count cutoff to label as TAM. In the Oxford Imperial DS
cohort study with a prospective follow-up of 200 DS neonates, 97.5% had blasts in
the peripheral blood, and 8.5% had GATA1 mutations. All mutation-positive neonates had a blast count of more than 10%. Three
percent of the cohort had blasts more than 10% but not detected GATA1 mutation. However, none of the mutation-negative children had clinical features of
TAM and did not develop myeloid leukemia even after a follow-up of 35 months.[5] So, a cutoff of >10% can be taken to screen for GATA1 mutation in neonates suspected to have TAM. Silent TAM is an entity in which there
are no clinical or hematological features of TAM despite minor clones carrying GATA1 mutation. They will have low (<10%) peripheral blood blasts.[2] The risk of developing myeloid leukemia in silent TAM is very rare.[7]
Although the appropriate time for blood smear examination for peripheral blood blasts
percentage in DS is 3 days of life, this is often not possible in developing countries.
The peripheral blood blasts will clear rapidly, even within a week. Though most of
the TAM is usually detected in the first week of life, where 10% blast percentage
is appropriate, the cutoff of 10% may not be appropriate in infants presenting late.
In most cases, TAM resolves by the age of 3 months; some may take up to 6 months.
It varies from 2 to 194 days with a mean of 58 days.[8]
[9]
GATA1 is a member of the GATA family, which has a common zinc finger domain that recognizes
the nucleotide sequence motif GATA.[10] It plays a main role in the hematopoiesis of erythroblasts, megakaryocytes, mast
cells, and eosinophils. GATA1 gene is located in the X chromosome. Normal GATA1 protein consists of three domains: an N-terminal zinc finger domain, a C-terminal
zinc finger domain, and a transcriptional activation domain N-terminal portion.[11] The normal GATA1 gene consists of 6 exons. Inherited mutations of GATA1 can lead to X-linked thrombocytopenia, X-linked thrombocytopenia with thalassemia,
and some forms of congenital erythropoietic porphyria.[12] In contrast, the somatic mutations in DS lead to TAM and DS-AMKL. The incidence
of somatic mutations is equal in both males and females.[12] The majority of somatic mutations in DS occur in exon 2 (97%) and the remaining
in exon 3.1, which results in the formation of a truncated GATA1s protein, leading to an aberrant megakaryopoiesis.[13]
GATA1 mutation can be detected by Sanger sequencing, denaturing high-performance liquid
chromatography, and NGS. The sensitivity of NGS is superior when compared with other
techniques. We are reporting a novel mutation causing a splice variant in Intron 2
c.220+1G>T (ENST00000376670.3) detected by NGS in our index case.
TAM's clinical presentation varies from just an incidental finding to a very sick
presentation with multiorgan failure. The usual clinical presentation includes hepatomegaly,
splenomegaly, pleural effusion, pericardial effusion, jaundice, ascites, respiratory
distress, skin rash, coagulopathy, and multiorgan failure. TAM can manifest in fetal
life with hydrops or other manifestations similar to the postnatal presentation.[8]
[14] The hematological abnormalities commonly seen are leukocytosis and blasts in peripheral
blood. Platelet count may be normal, elevated, or reduced. Thrombocytopenia is not
common in neonates with TAM when compared with DS without TAM. None of the clinical
features are specific to TAM. Our index case presented with hyperleukocytosis, and
he developed thrombocytopenia during the hospital stay.
Flowcytometry of TAM children shows a variable expression of stem cell markers (CD34/117),
myeloid markers (CD33/13), platelet glycoproteins (CD36, CD42, CD61), and aberrant
expression of CD56 and CD7. It is challenging to distinguish TAM and acute megakaryocytic
leukemia (AMKL) from flow cytometry and bone marrow findings. Age of diagnosis can
be a clue toward a TAM/AMKL because both are a continuum of the same disease.
More than 80% of TAM resolve completely, while 20 to 30% evolve into MDS/DS-AMKL.
Remission is observed by normalization of blood counts and blast clearance, followed
by the resolution of clinical symptoms like organomegaly. DS-AMKL can occur after
remission or progress into AMKL with persistent abnormal blood parameters with an
intervening MDS-like picture. Mortality due to TAM constitutes ~20% primarily due
to hepatic fibrosis leading to liver failure. Other causes include cardiorespiratory
failure, renal failure, and infection.[8]
Though TAM is a self-limiting disease, delaying treatment when indicated can result
in a fatal outcome. Tunstall et al have found that most clinicians are hesitant in
starting chemotherapy considering the self-limiting nature of the disease, which leads
to a significant delay in the initiation of life-saving treatment.[7] BFM (Berlin-Frankfurt-Münster) group recommended treatment with low-dose cytarabine
0.5 to 1.5 mg/kg/day for 3 to 12 days in TAM presenting with thrombocytopenia, cholestasis/liver
dysfunction and white blood cell (WBC) count >50,000/ mm3. Low-dose cytarabine was not associated with significant toxicity.[7]
Muramatsu et al have reported that WBC count >1 lakh/mm3 and anasarca at diagnosis of TAM are the risk factors for early death. They found
statistically significant difference in 1 year survival rate in TAM who presented
with WBC count of more than 1 lakh/mm 3 among those treated with low-dose cytarabine versus untreated (78.3 vs. 38.5%).[15]
Children's oncology group recommends treatment in multiorgan failure, WBC count >100×109/L or evidence of leukostasis, hepatopathy (characterized by conjugated bilirubin
>83 µmol/L, ascites or massive hepatomegaly), massive hepatosplenomegaly causing respiratory
or feeding compromise, hydrops fetalis, pleural or pericardial effusions, renal failure,
and disseminated intravascular coagulation. Treatment includes low-dose cytarabine
in twice daily dose as mentioned above for 5 to 7 days or 3.3 mg/kg/day as a continuous
infusion for 7 days.[7] Our index case presented with WBC count of more than 1 lakh /mm3 and hepatosplenomegaly, causing respiratory compromise, and received cytarabine at
1 mg/kg twice a day for 7 days. In patients with persistent severe liver dysfunction,
repeated courses of cytarabine can be given, but treatment should not be given solely
based on hepatomegaly because it might take months to resolve. There is no prophylactic
role of cytarabine to prevent future occurrence of AMKL.[7]
It is advisable to follow up TAM children with three monthly clinical examinations,
peripheral smear for the blasts, complete blood count until the age of 2 years, and
then six-monthly till 4 years of age. With additional cytogenetic abnormalities, TAM
can evolve into myeloid leukemia, usually before the age of 5 years.
Conclusion
TAM is exclusive to DS and warrants a screening with complete blood counts and peripheral
smear examination in the first week of life, preferably by day 3 because of rapid
clearance of blasts. Testing for GATA1 mutation is necessary for children with > 10% blasts for identifying children at
a future risk of myeloid leukemia. It is important to know the prevalence and type
of GATA1 mutation prevailing in our country as there is a paucity of data regarding GATA1 mutation. Considering the minimal toxicity of low-dose cytarabine and risks outweighing
benefits, timely treatment should be initiated when indicated for a better outcome.
This case report highlights the novel GATA1 mutation and treatment strategy in TAM.
