Tohoku J. Exp. Med., 2005, 206(3)

Genetic Analysis of Shwachman-Diamond Syndrome: Phenotypic Heterogeneity in Patients Carrying Identical SBDS Mutations

TAKAKO KAWAKAMI, TETSUO MITSUI, MASAYO KANAI, EMI SHIRAHATA, DAI SENDO, MIYAKO KANNO, MIZUKA NORO, MIKIYA ENDOH,¹ ASAHITO HAMA,² CHIKAKO TONO,³ ETSURO ITO,³ SHIGERU TSUCHIYA,⁴ YUTAKA IGARASHI,⁵ DAIKI ABUKAWA⁶ and KIYOSHI HAYASAKA

Department of Pediatrics, Yamagata University School of Medicine, Yamagata, ¹Department of Pediatrics, Iwate Medical University, Morioka, ²Department of Pediatrics, Nagoya University School of Medicine, Nagoya, ³Department of Pediatrics, Hirosaki University School of Medicine, Hirosaki, ⁴Department of Pediatric Oncology, Institute of Development, Aging and Cancer, Tohoku University, Sendai, ⁵Igarashi Pediatric Clinic, Sendai, and ⁶Department of General Pediatrics, Miyagi Children's Hospital, Sendai, Japan

Shwachman-Diamond syndrome (SDS) is a rare hereditary disorder characterized by pancreatic exocrine insufficiency, bone marrow dysfunction and skeletal changes. Recently, the cause of SDS was identified as mutations of Shwachman-Bodian-Diamond syndrome gene (SBDS) and most mutations are caused by gene conversion between SBDS and its highly homologous pseudogene. Clinical variations especially in skeletal and bone marrow abnormalities are well known in this syndrome. To study the relationship between SBDS mutation and its clinical features, we analyzed 9 Japanese patients including one sibling and detected the three different SBDS mutations in 7 patients: a mutation that disrupts the donor splice site of intron 2, deletes 8bp of the exon 2 and produces premature termination (258+2 T > C), a dinucleotide change that replaces a lysine at 62nd amino acid to a termination codon (183-184 TA > CT), and a 4-bp deletion that causes premature termination by frameshift (292-295 delAAAG). The 5 patients represent compound heterozygotes of the 258+2 T > C and 183-184 TA > CT mutations. One patient is a compound heterozygote of the 258+2 T > C and 292-295 delAAAG mutations, and in the remaining one case only a 258+2 T > C mutation could be detected. Thus, the 258+2 T > C and 183-184 TA > CT mutations are prevalent among Japanese patients. No mutations were found in two cases, despite the clinical features. Of the 7 patients with SBDS mutations, persistent hematologic abnormalities and skeletal changes were not observed in 3 and 2 patients, respectively. Notably, clinical variations are present even among the patients with the identical genotype: compound heterozygotes of the 258+2 T > C and 183-184 TA > CT mutations. Further study will be required to explain the clinical heterogeneity.

keywords —— Shwachman-Diamond syndrome; SBDS; mutations; clinical heterogeneity

© 2005 Tohoku University Medical Press

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Correspondence: Tetsuo Mitsui, M.D., DM Sci., 2-2-2 Iida-nishi, Yamagata 990-9585, Japan.

e-mail: tmitsui@med.id.yamagata-u.ac.jp