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Case Report
A Case of Bernard-Soulier Syndrome Associated with 22q11.2 Deletion Syndrome
Clin Pediatr Hematol Oncol 2023;30:95-8.
Published online October 31, 2023
© 2023 Korean Society of Pediatric Hematology-Oncology

Oh Cheol Kwon1, Su Hyun Yoon2, Sung Han Kang2, Hyery Kim2, Kyung-Nam Koh2 and Ho Joon Im2

1Department of Pediatrics, Asan Medical Center Children’s Hospital, University of Ulsan College of Medicine, 2Division of Pediatric Hematology/Oncology, Department of Pediatrics, Asan Medical Center Children’s Hospital, University of Ulsan College of Medicine, Seoul, Korea
Correspondence to: Ho Joon Im
Division of Pediatric Hematology/Oncology, Department of Pediatrics, Asan Medical Center Children’s Hospital, University of Ulsan College of Medicine, 88 Olympic-ro 43-gil, Songpa-gu, Seoul 05505, Korea
Tel: +82-2-3010-3371
Fax: +82-2-473-3725
E-mail: hojim@amc.seoul.kr
ORCID ID: orcid.org/0000-0001-8799-4068
Received August 21, 2023; Revised October 11, 2023; Accepted October 24, 2023.
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract
22q11.2 deletion syndrome (22q11.2DS) is a disorder caused by microdeletions in the long arm of chromosome 22. It is one of the most common chromosomal microdeletion disorders. Clinical symptoms are caused by heterozygous deletion of chromosome 22q11.2 and include congenital heart diseases and palatal abnormalities. Bernard-Soulier syndrome (BSS) is a rare autosomal recessive bleeding disorder caused by deficiency of the glycoprotein Ib-IX-V complex (GPIb-IX-V), the receptor for von Willebrand factor. Glycoprotein Ib-beta (GPIbβ) gene mutation is one of the causes of BSS, and the GP1bβ gene is located on chromosome 22q11.2. Most 22q11DS patients do not have a bleeding issue since most of them have heterozygous deletion of the GPIbβ gene. However, we report a case in which a child with 22q11.2DS visited the hospital with subgaleal hemorrhage and was diagnosed with Bernard-Soulier syndrome with GPIbβ gene mutation by a platelet aggregation test and genetic sequencing.
Keywords: Distal chromosome 22q11.2 deletion syndrome, Bernard Soulier syndrome
Introduction

22q11.2 deletion syndrome (22q11.2DS) presents with various clinical symptoms and several congenital anomalies, including congenital heart diseases, palatal abnormalities, immune deficiencies, craniofacial features, and developmental delay. Bernard-Soulier syndrome (BSS) is an extremely rare autosomal recessive genetic disease, characterized by giant platelet cells, thrombocytopenia and prolonged bleeding time. BSS is caused by a problem with glycoprotein Ib-IX-V, a platelet receptor complex that attaches to von Willebrand factor (vWF). The gene encoding glycoprotein Ib-beta (GPIbb) protein exists on chromosome 22q11.2. Because the majority of 22q11DS patients have a heterozygous deletion of the GPIbb gene, they are not usually diagnosed with BSS, which is expressed as an autosomal recessive disorder. We report a case of Bernard-Soulier syndrome diagnosed in a patient with 22q11.2 deletion syndrome who showed a severe bleeding tendency. Abnormal platelet aggregation tests and gene mutations confirmed by gene sequencing confirmed the presence of BSS. The Institutional Review Board of the Asan Medical Center approved this case report (IRB approval no: 2023-1042).

Case Report

A 5-year-old Korean boy presented with headache and increased head circumference (>99%). His symptoms gradually worsened over 1 week. He had no history of trauma, and physical examination revealed no head in-juries. At 1 month of age, he underwent heart surgery for an atrial septal defect and a ventricular septal defect. At the time, his platelet count was around 80-100×103/mL. He underwent surgery to repair a cleft palate at age 4. Thrombocytopenia had been present since birth, and platelet transfusion was performed for surgeries. Addi-tionally, he had a history of frequent infections, speech impairment, and facial dysmorphism (hypertelorism, narrow palpebral fissure, bulbous nose, hypernasal voice). Conventional karyotyping confirmed normal chromosomes, but fluorescent in situ hybridization (FISH) confirmed del(22)(q11.2q11.2)(TUPLE1-), and he was diagnosed with 22q11.2 deletion syndrome.

At this presentation, peripheral blood tests showed thrombocytopenia (77×103/mL) and anemia (Hb 8.5 g/dL), and white blood cells were normal. Mean platelet volume could not be measured, but large platelets were often observed on microscopy. The bleeding time, prothrombin time, partial thromboplastin time, thrombin time, and fibrinogen levels were all normal. Subgaleal hemorrhage was confirmed on a brain computed tomography (Fig. 1), and there were no findings of skull fracture or bleeding at other sites. Additional tests were conducted for the possibility of a bleeding disorder. Factor VIII level, Von Willebrand factor antigen, and ristocetin cofactor activity were normal. In the platelet aggregation test, using a platelet function analyzer-100, normal plasma platelet aggregation was observed when exposed to ADP, collagen and epinephrine, but a hypoaggregation response was shown to ristocetin (maximal aggregation of 16.4%). These results suggested the diagnosis of Bernard-Soulier syndrome.

Figure 1. Large amount of subgaleal hematoma in the right side scalp, with extension to left forehead, seen on brain computed tomography at the time of hospitalization.

Multiplex ligation-dependent probe amplification (MLPA) was performed to analyze the patient’s DNA sequence. On one side of the patient’s chromosome, a 1.9 Mb deletion containing the low-copy repeats (LCR) A and LCR B regions of the chromosome 22q11.2 region was identified, including the GPIbb gene. This refers to the child’s previously known 22q11.2 deletion syndrome. On the other side of the chromosome, the mutation c.[124C>T](p.[Arg42Cys]) of the GPIbb gene was confirmed (Fig. 2). Family genetic testing confirmed that the mother was a carrier with the same mutation.

Figure 2. Partial sequence of GPIbb gene. The upper part is the normal control group, and the lower part is the patient’s gene sequence, con-firming the presence of mutation c.[124C>T]. A, adenine; T, Thy-mine; C, Cytosine; G, Guanine.

Finally, he was diagnosed with BSS accompanied by 22q11.2DS, and received multiple platelet transfusions. After 2 weeks of hospitalization, the headache and head circumference improved, and he was discharged without additional bleeding. Brain computed tomography also showed improvements in the subgaleal hemorrhage (Fig. 3). Later, when he was 10 years old, he was admitted to the hospital with a hematoma in his left buttock caused by a fall. Platelet was transfused, but the bleeding did not stop, so embolization was done instead. He also has scoliosis requiring surgery, but he is under observation without surgery due to the high risk of bleeding.

Figure 3. Two months later, brain computed tomography showed marked decreased amount of subgaleal hemorrhage since the last exam.
Discussion

22q11.2 deletion syndrome, previously called DiGeorge or velocardiofacial syndrome, is now known to show highly variable phenotypes [1]. 22q11.2 DS is rare but is one of the most common chromosomal microdeletion disorders. The estimated live-birth prevalence has a wide range from 1.7 to 4.7 per 10,000 live births [1,2]. 22q11.2DS is an autosomal dominant genetic disease inherited with a 50% probability, but 90% of cases are known to occur de novo.

Our patient had congenital heart disease (ventricular septal defect, atrial septal defect), cleft palate, frequent infections, facial dysmorphism (hypertelorism, narrow palpebral fissure, bulbous nose, hypernasal voice), developmental delay, and scoliosis as clinical symptoms. His parents had normal chromosomes, so he was a de novo case.

22q11.2DS patients often show thrombocytopenia, and the hematological changes seen in 22q11.2DS may be due to the genetic disorder itself or may be secondary findings accompanying clinical findings such as immunodeficiency [3,4]. Some 22q11DS patients have a decrease in platelet count and an increased platelet size and volume [5]. Most of them are asymptomatic and do not show a severe bleeding tendency. Our patient also had thrombocytopenia of 100×103/mL from birth and was misdiagnosed with idiopathic thrombocytopenic purpura (ITP) and received intravenous immunoglobulin (IVIg) treatment. Although his platelet size was not quantitatively measured, microscopy revealed the presence of large platelets. In the absence of severe thrombocytopenia, subgaleal hemorrhage without trauma suggested the possibility a bleeding disorder. Additional tests confirmed the reduced response to ristocetin, an agonist to stimulate vWF-platelet glycoprotein Ib interactions, that is not corrected by the addition of normal plasma in a platelet aggregation study. This characteristic is consistent with findings observed in BSS. Previously, cases of BSS in which platelet aggregation was reduced by ristocetin were reported in patients with 22q11DS [6,7]. However, it was also reported that platelet aggregation could be reduced due to heterozygous loss of platelet GPIbb protein by chromosome 22q11.2 deletion [8].

Subsequently, flow cytometry has been used as a confirmatory test for BSS. Marked reduction of glycoprotein can be confirmed through flow cytometry analysis using platelet glycoprotein specific monoclonal antibodies. However, because BSS is extremely rare, flow cytometry is often difficult to perform. Instead, many causative genes have been identified, so when clinical suspicion is present, the diagnosis is often confirmed through genetic testing for platelet glycoprotein. Therefore, we also used genetic analysis using Multiplex Ligation-dependent Probe Amplification (MLPA) to diagnose BSS. To detect mutations including gene deletions/duplications, Southern Blot and FISH techniques have been widely used. However, these methods are time consuming and have limitations in finding small intragenic rearrangements. However, MLPA is much faster and cheaper, and has high resolution that can detect even single exon deletion/dupli-cations, so MLPA has recently been preferred for detection of gene mutations.

As a result, in one chromosome, a large deletion of 22q11.2, including the GPIbb gene region, was identified. In the other chromosome, a missense mutation c.[124C>T](p.[Arg42Cys]) in the GPIbb gene was identified. This is a novel gene mutation that has not been reported before. So, we confirmed that there were deletions and mutations in both alleles of the GPIbb gene. We assumed that the mutated GPI transcripts were improperly translated, preventing platelet glycoprotein Ib from binding to vWF and causing subgaleal hemorrhage. To establish the pathogenicity of the novel mutation in the GPIbb gene that has been found, it will be necessary to conduct molecular confirmation using flow cytometry and do further study. Nevertheless, based on the patient’s clinical symptoms and the observed hypoaggregation response to ristocetin in the platelet aggregation test, it may be inferred that the identified missense mutation c.[124C>T](p.[Arg42Cys]) is very probable to represent a pathogenic variation of BBS.

There are a few previous case reports of combinations of haploinsufficiency of the GPIbb gene by chromosome 22 microdeletion and allelic mutation of chromosome 22 [6,9]. However, these reports only molecularly confirmed the 22q11.2 deletion and did not confirm the mutation of the GPIbb gene. Our report is the only case report that confirmed the GPIbb gene mutation and obtained family genetic test results.

In conclusion, we report a patient with 22q11.2 deletion syndrome who also had a GPIbb gene mutation, which is associated with Bernard-Soulier syndrome. This case highlights an association of BSS with 22q11.2DS. Although bleeding events in 22q11.2DS patients are rare, physicians should consider the possibility of BSS and perform platelet aggregation tests or DNA sequencing if bleeding symptoms are observed. Proper preparation for hemostasis should be undertaken if surgical procedures are planned for these patients.

Conflict of Interest Statement

The authors have no conflict of interest to declare.

References
  1. McDonald-McGinn DM, Sullivan KE, Marino B, et al. 22q11.2 deletion syndrome. Nat Rev Dis Primers 2015;1:15071.
    Pubmed KoreaMed CrossRef
  2. Blagojevic C, Heung T, Theriault M, et al. Estimate of the contemporary live-birth prevalence of recurrent 22q11. a cross-sectional analysis from population-based newborn screening. CMAJ Open 2021;9:E802-9.
    Pubmed KoreaMed CrossRef
  3. Kato T, Kosaka K, Kimura M, et al. Thrombocytopenia in patients with 22q11. 2 deletion syndrome and its association with glycoprotein Ib-beta. Genet Med 2003;5:113-9.
    Pubmed CrossRef
  4. Rosa RF, Rosa RC, Dos Santos PP, Zen PR, Paskulin GA. Hematological abnormalities and 22q11. 2 deletion syndrome. Rev Bras Hematol Hemoter 2011;33:151-4.
    Pubmed KoreaMed CrossRef
  5. Latger-Cannard V, Grégoire MJ, Bensoussan D, et al. Frequency of thrombocytopenia and large platelets correlates neither with conotruncal cardiac anomalies nor immunological features in the chromosome 22q11. 2 deletion syndrome. Eur J Pediatr 2004;163:327-8.
    Pubmed CrossRef
  6. Nakagawa M, Okuno M, Okamoto N, Fujino H, Kato H. Bernard- Soulier syndrome associated with 22q11. 2 microdeletion. Am J Med Genet 2001;99:286-8.
    Pubmed CrossRef
  7. Kunishima S, Imai T, Kobayashi R, Kato M, Ogawa S, Saito H. Bernard-Soulier syndrome caused by a hemizygous GPIbb mutation and 22q11. 2 deletion. Pediatr Int 2013;55:434-7.
    Pubmed CrossRef
  8. Liang HP, Morel-Kopp MC, Curtin J, et al. Heterozygous loss of platelet glycoprotein (GP) Ib-V-IX variably affects platelet function in velocardiofacial syndrome (VCFS) patients. Thromb Haemost 2007;98:1298-308.
    Pubmed CrossRef
  9. Souto Filho JTD, Ribeiro HAA, Fassbender IPB, Ribeiro JMMC, Ferreira Júnior WDS, Figueiredo LCS. Bernard-Soulier syndrome associated with 22q11. 2 deletion and clinical features of DiGeorge/velocardiofacial syndrome. Blood Coagul Fibrinolysis 2019;30:423-5.
    Pubmed CrossRef


October 2023, 30 (2)
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  • Ho Joon Im