Page 86 - Haematologica Vol. 107 - September 2022

ARTICLE - Inherited cytopenias in children Results
Clinical diagnosis
During the study period, 189 DNA samples of children presenting with persistent cytopenias from twelve pedi- atric hematology centers in Israel were sent to the Mol- ecular Hematology Laboratory in Schneider Children's Medical Center of Israel. The clinical referral diagnosis, de- fined by the treating hematologists, was IBMFS (48 pa- tients), MDS (26 patients), SAA (31 patients), isolated neutropenia (51 patients) and isolated thrombocytopenia (33 patients) (Table 1).
Most patients were Israelis (96%). Eighty-seven (46%) of our patients were of non-Jewish origin, mainly Arabic, which is considerably higher than their proportion in the Israeli population (26.1%).29 Almost one-third of the pa- tients originated from consanguineous families (Online Supplementary Table S2). The median age at clinical pres- entation was 1 year (range, 0-20) and the median age at referral was 8 years (range, 0.5-41). Patients were referred at a median of 5.8 years following their first clinical pres- entation.
Genetic diagnosis
Of the 189 children referred for genetic evaluation, 49 had a clinical presentation suggestive of a specific diagnosis and, therefore, Sanger sequencing of commonly mutated genes was initially performed (Online Supplementary Fig- ure S1). Diagnosis was reached for 13 (6 were homozygous for FANCA variants, 5 had heterozygous variants in RPS19 and 2 were compound heterozygous for variants in the SBDS gene). Fourteen patients with a negative Sanger se- quencing result were further evaluated using our NGS panel and 22 did not undergo further genetic workup (11 recovered, 6 are clinically stable and are being followed, 4 underwent successful HSCT and one was lost to follow- up). In total, 140 patients were initially directly referred for NGS panel diagnosis (Online Supplementary Figure S1). Overall, P/LP variants were identified in 59 of 189 patients (31.2%). Of the diagnosed patients, 47 (24.9% of the whole cohort and 79.7% of the diagnosed patients) had an in- herited predisposition to leukemia, while nine had IT af- fecting platelet production and function, and three had congenital neutropenia not currently known to cause leukemia predisposition (Figure 1; Tables 2 to 7; Online Supplementary Table S3). Eleven sequence variants, in ten patients, were defined as VOUS; these patients are not in- cluded in the analyses (Online Supplementary Table S4). In addition, 12 patients with a clinical and genetic diagno- sis compatible with benign ethnic neutropenia were not included in the analyses.
Overall, 28.6% of the patients had congenital anomalies, with a statistically significant higher proportion among pa- tients that were genetically diagnosed (39% and 23.8% in
O. Gilad et al. diagnosed and undiagnosed patients, respectively; P-
value =0.038, Online Supplementary Table S2).
Patients presenting with inherited bone marrow failure syndromes
Of 48 patients who were referred with IBMFS, five had in- creased chromosomal breakage and three had short te- lomeres (Table 2; Table 3). In 29 of 48 (60.4%) patients, genetic variants explaining the clinical phenotype were found; of those, 27 had classical and two had non-classi- cal IBMFS. Twelve patients were diagnosed with FA: ten were homozygous for FANCA variants, one had a homozy- gous FANCS (BRCA1) variant and one had a FANCE variant. Ten patients were diagnosed with DBA: six had heterozy- gous variant in RPS19, and one each had a heterozygous variant in the genes RPS10, RPS15, RPS26 and RPS28. One additional patient carried a homozygous variant in the CECR1 gene, which caused a DBA-like phenotype. Four pa- tients with DC had genetic alterations in the TERT, TERC, WRAP53 and TINF2 genes. Two patients had non-classical IBMFS, with homozygous variants in the ERCC6L2 and MYSM1 genes (Figure 1; Table 3; Online Supplementary Table S3). Both were of consanguineous Arab families. The patient with the biallelic ERCC6L2 variant also had con- genital anomalies and developmental delay. The patient with a MYSM1 homozygous variant had early onset pan- cytopenia, with a hypocellular marrow and a paucity of red cell precursors and mild developmental delay and short stature. This phenotype was similar to that pre- viously described for a few individuals.30,31
Patients presenting with myelodysplastic syndrome
Twenty-six patients in this study had MDS, including 19 with RCC and seven with MDS and excess blasts (MDS- EB). Germline disease-causing variants were found in six of the 19 patients with RCC (31.6%). Three patients had variants in the SAMD9L gene, two in ERCC6L2 and one in ANKRD26 (Figure 1; Table 4; Online Supplementary Table S3). No germline pathogenic variants were detected in the seven patients presenting with MDS-EB. All three patients diagnosed with SAMD9L variants had monosomy 7, which was subsequently resolved in two (7 months and 4 years later) (Figure 1). The two patients with biallelic variants in ERCC6L2 originated in consanguineous Arab families with no known relatives with MDS. Both were referred with pancytopenia and had BM dysplastic changes.
One child presented with a variant in the initiation codon of ANKRD26. He was born at term following a normal preg- nancy, with a low birth weight (1.9 kg), a single umbilical artery and dysmorphic features. He had severe recurrent infections including Pneumocystis Jiroveci and Cytomega- lovirus lung infections. Rechavi et al.32 extensively studied this patient, who is now 8 years old, and found a mosaic monosomy 21, as well as defects in immunoglobulin
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