Gaucher disease (GD) is an autosomal recessive disease caused by the deficiency of β-glucocerebrosidase, a lysosomal enzyme in monocytes and macrophages that catalyzes hydrolysis of β-glucocerebroside to glucose and ceramide. The deficiency of β-glucocerebrosidase leads to the accumulation of its substrates in lysosomes followed by progressive complications in the liver, spleen, lung, bone, bone marrow, and nervous system.
There are 3 subtypes of GD classified by the presence and extent of central nervous system (CNS) involvement and prognosis. Type 1 GD does not include CNS manifestations. Type 2 is associated with acute onset in infancy and severe CNS manifestations. Type 3 develops chronically with mild CNS symptoms.
The definite diagnosis of GD must be based upon experimental proof of the low activity of β-glucocerebrosidase in total leukocytes or mononuclear cells or in fibroblasts cultured from skin biopsies. Genotype identification of the β-glucocerebrosidase gene (GBA) supports the definite diagnosis of GD. Genotype identification seems worthy even for the patients who had already been diagnosed with GD for three reasons. First, the patients with type 3 GD maintain relatively normal β-glucocerebrosidase activity and are sometimes difficult to diagnose by the latter parameter only. GBA genotype testing should be an essential clue to diagnose GD in such patients. Second, GBA genotype identification is important to determine if the patient with GD is a candidate for chaperone therapy, which is effective for patients with GD with particular mutations, including N370S (c.1226A>G) and F2131 (c.754T>A).[5,6] Third, GBA genetic analysis may predict the patient's prognosis because significant correlations between clinical phenotypes and GBA mutations have been reported. For example, 62% of the patients with type 1 GD have N370S allele, whereas most patients with types 2 and 3 GD have L444P alleles (48% and 69%, respectively). Tajima et al reported that the diagnosis of type 1 GD may change later into type 3 if the patients have L444P allele in GBA. Moreover, because GD is an inherited disease, the patient's genotype identification may enable the early diagnosis of GD and early start of the treatment of the patient's children.
There are several therapeutic options for GD, including enzyme replacement therapy (ERT), substrate reduction therapy, chaperone therapy, and allogeneic hematopoietic stem-cell transplantation. ERT has the longest history among them. Since mid-1990's, imiglucerase, a recombinant form of β-glucocerebrosidase, has been administrated as an ERT drug to treat the patients with GD. Recently, velaglucerase α, which is driven from a gene-activated human cell line, has been approved as a new ERT treatment in Japan.
Here, we report a Japanese patient who presented with slight anemia and thrombocytopenia without major complaints and was initially diagnosed at the preoperative 18F-deoxyglucose positron emission tomography/computed tomography (FDG PET/CT) scan with gastric cancer. Ultimately, the patient was diagnosed with type 1 GD caused by the novel K157R (c.587A>G) mutation in GBA.
2 Case report
A 69-year-old female was referred to our hospital for the treatment of gastric cancer invading the submucosa at the gastric angle, which had been suggested by upper endoscopy during periodic medical checkup. She had no major complaints and was under treatment for hyperlipidemia and type 2 diabetes mellitus. She had a history of left ovarian cancer followed by left ovariectomy. The marriage of her deceased parents was consanguineous.
Her blood test was within normal limits except for slight anemia (hemoglobin 11.8 g/dL), mild thrombocytopenia (platelets 14.8 × 104 /μL), and high level of ferritin (553.7 ng/mL) (Table 1). Preoperative 18F-FDG PET/CT found strong bilateral accumulations in the bone marrow of humeri and femora and in the paraabdominal aortic lymph nodes in addition to a weaker accumulation in the stomach but without accumulations in the gastric lymph nodes or hepatosplenomegaly (Fig. 1A). Those findings were considered as comorbidity in the bone marrow. The subsequent bone marrow aspiration revealed that there were no pathologic cells that would indicate gastric cancer metastasis but abnormally large foamy histiocytes occupying 4% of total cellularity that were stained positively for CD68, CD163, periodic acid Schiff, and acid phosphatase but were negative for anti-pan cytokeratin staining, which suggested Gaucher cell phenotype, were found (Fig. 1B–D). Further electron microscopy investigation of the bone marrow specimen elucidated that the large foamy cells had irregular extended cytoplasm filled with abundant lysosomes, which were fully occupied by tubular-form structures, a feature commonly seen in lysosomal diseases (Fig. 2A).
The preoperative histopathology of gastric biopsy by upper endoscopy suggested moderately to poorly differentiated adenocarcinoma infiltrating into the gastric submucosa. 18F-FDG PET/CT found a limited accumulation in the paraabdominal lymph nodes but no paragastric lymph nodes. Thus, the patient's gastric cancer was considered as operative, so distal gastrectomy and paraabdominal lymphadenectomy were performed.
Postoperative histopathologic examination of the extracted stomach revealed that the gastric cancer was poorly differentiated adenocarcinoma and that paraabdominal lymph nodes included abnormal sheet-like proliferation of foamy cells, indicating a lysosomal disease, for example, GD, as was also suggested by the abnormal foamy cells of the aspirated bone marrow specimen (Fig. 2B).
As a result of those findings, GD was highly suspected. The diagnosis of GD was confirmed by the low activity of β-glucocerebrosidase and concomitant acid phosphatase elevation (Table 2). Additionally, after the diagnosis, we sent the patient's blood sample to the Tottori University for the genotypic test of GBA. GBA gene was analyzed using direct sequencing according to the methods described by Mitsui et al. The analysis found the compound heterozygote mutations of K157R (c.587A>G) on exon 6 and RecNciI, including L444P (c.1448T>C), A456P (c.1483G>C), V460 (c.1497G>C), on exon 11 of the GBA gene (Fig. 3).
The patient did not develop any neurologic symptoms, and no abnormalities were found by head magnetic resonance imaging, which confirmed the classification of GD as type 1.
The ERT with every-other-week intravenous infusion of 60 units per kilogram of velaglucerase α, a recombinant β-glucocerebrosidase that was most recently approved in Japan, was started after the diagnosis of GD. Hemoglobin and platelet levels were restored at 2 and 3 months after velaglucerase α administration, respectively. Bone marrow samples collected 10 months after velaglucerase α administration showed reduction of Gaucher cells in bone marrow to 2% of total cellularity. The patient has received ERT for 16 months without any side effect up to the present.
This case report was approved by the ethics committee of Shiga University of Medical Science, Shiga, Japan and written informed consent was obtained.
To the best of our knowledge, this is the first report of the novel K157R (c.587A>G) mutation in GBA that caused GD and of the use of 18F-FDG PET/CT for suggestive diagnosis of GD in a patient with slight anemia and thrombocytopenia but no complaints.
The morbidity of GD in Japan is much less than in Western countries (1 per 3.3 × 105 and 1.16 per 1 × 105 live births, respectively), and the information about Japanese patients with GD is relatively limited.[11,12] Tajima et al reported that 58% of Japanese patients with GD develop types 2 or 3 GD, which is accompanied by neurologic symptoms (24% and 34% of cases, respectively). In contrast, only 1% or 5% of patients with GD globally are diagnosed as types 2 or 3 GD, respectively, according to the worldwide registry reported by Charrow et al. As the age at diagnosis for the patients with types 2 and 3 GD is usually younger than that of patients with type 1 GD, Japanese patients are diagnosed with GD at a relatively younger age. Thus, in Japan, it is quite difficult to diagnose GD in adult individuals who present with slight anemia and thrombocytopenia but exhibit no neurologic manifestations, splenomegaly, bone pain, or other typical GD symptoms.
In our case, 18F-FDG uptake in the bone marrow was the important clue to suspect GD. The correlation between 18F-FDG accumulation in bone marrow and GD was previously reported by Erba et al. In their report, all 7 enrolled patients who had been diagnosed previously as type 1 GD had 18F-FDG accumulation in the bone marrow. Furthermore, the score based on the extension and magnitude of 18F-FDG uptake in the bone marrow was highly correlated to the clinical severity score. However, we believe that no case reports that actually utilized 18F-FDG PET/CT for GD diagnosis had been published before our present case.
Moreover, our case is the first report of K157R mutation in GBA. GBA is located on 1q21; its total length is 7 kb, and it has 11 exons, and there is a highly homozygous pseudogene that easily recombines with GBA. Over 300 mutations causing GD have been reported. RecTL (c.1342G>C, c.1448T>C, c.1483G>C, and c.1497G>C) and RecNciI (c.1448T>C, c.1483T>G, and c.1497G>C) are the well-known recombinant mutations between GBA and that pseudogene.
The mutations causing GD are significantly associated with patient's ethnicity. N370S (c.1226A>G) is common among Ashkenazi Jewish patients, in which it is found in approximately 70% of cases, whereas in an Asian cohort, this mutant allele has been found only in 12% of cases. The prevalence of F2131 (c.754T>A) and L444P (c.1448T>C) among Japanese patients is about 41% and 11%, respectively, whereas in Ashkenazi Jewish patients, those mutations are relatively rare. Genetic screening for 8 common mutations, including N370S, L444P, F2131, R463C (c.1504C>T), 84GG (c.84dupG), IVS2+1 (c.115+1G>A), D409H (c.1342G>C), and RecNciI, can identify causative mutations in most Ashkenazi Jewish patients. However, this gene screening cannot recognize mutations in 39% of Japanese patients. To detect mutations unidentified by the gene screening, comprehensive resequencing of the GBA gene for all 11 exons is required.
To verify that K157R was responsible for GD in the patient studied, the heterozygous mutations of K157R and RecNciI were confirmed by using DdeI, a restriction enzyme recognizing double stranded deoxyribonucleic acids. However, our case report has a limitation in that it remained unclear whether the mutation was de novo or inherited, as we could not obtain genetic material of the patient's parents or other relatives. Assuming that K157R was inherited from the parents and was also passed to the patient's offspring, there should be a population carrying K157R in Japan. For such population, which could potentially develop GD, further investigation of this gene is needed.
In conclusion, our case demonstrated the utility of 18F-FDG PET/CT for GD diagnosis and suggested the existence of a population carrying K157R allele that causes GD in Japan. For such patients, 18F-FDG PET/CT is valid as the first step of diagnosis.
Data curation: Kaori Adachi, Ryota Nakanishi, Suzuko Moritani, Eiji Nanba.
Writing – original draft: Sakura Hosoba.
Writing – review & editing: Katsuyuki Kito, Yukako Teramoto, Kaori Adachi, Ryota Nakanishi, Ai Asai, Masaki Iwasa, Rie Nishimura, Suzuko Moritani, Masahiro Kawahara, Hitoshi Minamiguchi, Eiji Nanba, Ryoji Kushima, Akira Andoh.
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