CASE REPORT Hereditary non-spherocytic hemolytic anemia and severe glucose phosphate isomerase deficiency in an Indian patient homozygous for the L487F mutation in the human GPI gene Prashant Warang • Prabhakar Kedar • Kanjaksha Ghosh • Roshan B. Colah Received: 19 March 2012 / Revised: 28 May 2012 / Accepted: 6 June 2012 / Published online: 11 July 2012 Ó The Japanese Society of Hematology 2012 Abstract Homozygous glucose phosphate isomerase (GPI) deficiency is one of the most important erythroenzymopathies causing hereditary non-spherocytic hemolytic anemia (HNSHA). We report an Indian patient with HNSHA showing 85 % reduction in GPI activity resulting from a homozygous missense replacement g.1459C [ T in exon 16, leading to a substitution of the protein residue L487F mutation. This mutation has been detected previously in a compound hetero- zygous state along with another mutation in a GPI deficient patient elsewhere. To our knowledge, this is the first report of HNSHA associated with GPI deficiency with the homozygous L487F mutation, as well as the first report from India of GPI deficiency. Molecular modeling using the human crystal structure of GPI as a model was performed to determine how this mutation could affect enzyme structure and function. The enzyme is present in a dimeric form necessary for normal activity; the L487F mutation causes a loss of the ability of GPI to dimerize, which decreases the thermostability of the enzyme and results in significant changes in erythrocyte metabolism. Keywords GPI deficiency Á HNSHA Á Erythrocyte metabolism Á Glycolysis Á India Introduction Glucose phosphate isomerase (EC 5.3.1.9; GPI) is a dimeric enzyme that catalyzes the reversible inter-conversion of glucose-6-phosphate (G6P) and fructose-6-phosphate in the Embden–Meyerhof pathway. GPI is an essential enzyme for carbohydrate metabolism in all tissues and null expression of the murine GPI gene has been found to be lethal at the embryonic stage. GPI has been shown to play other biological roles as a neuroleukin, a neurotrophic factor for spinal and sensory neurons and a lymphokine product of lectin-stimu- lated T cells [1, 2]. An additional biological activity of GPI is to serve as a maturation inducer capable of mediating the differentiation of human myeloid leukemic HL-60 cells to terminal monocytic cells [3]. This finding suggests that GPI may also have other functions besides being involved in car- bohydrate metabolism. Majority of patients with GPI deficiency have chronic non- spherocytic hemolytic anemia of variable severity [4]. In the most severe case, GPI deficiency has led to hydrops fetalis [5]. In rare cases GPI deficiency is accompanied by mental retardation or neuromuscular symptoms [6]. The gene coding for human GPI (neuroleukin) is located on the long arm of chromosome 19. The cDNA sequence encodes 558 amino acid residues with a molecular mass of 63 kDa (protein bank accession number AAH04982). At the DNA level, thirty-one mutations causing GPI deficiency have been reported world- wide (missense/nonsense 29, Splicing 1, deletion 1) (human gene mutation database http://www.biobase-international. com). As an autosomal recessive inherited disorder, only het- erozygotes are asymptomatic and the homozygotes or com- pound heterozygotes present clinically with anemia. The crystal structure of human GPI has recently been determined [7]. Here we describe the first Indian family with GPI deficiency. Patient background The propositus was a 9-year-old female child belonging to the Muslim community and born of a non-consanguineous P. Warang Á P. Kedar Á K. Ghosh Á R. B. Colah (&) Department of Haematogenetics, National Institute of Immunohaematology, Indian Council of Medical Research, 13th Floor, New Multistoried Building, K.E.M Hospital Campus, Parel, Mumbai 400012, India e-mail: colahrb@gmail.com 123 Int J Hematol (2012) 96:263–267 DOI 10.1007/s12185-012-1122-x