A clinical and molecular study of a Bedouin family with dysmegakaryopoiesis, mild anemia, and neutropenia cured by bone marrow transplantation

Expansion of the clinical phenotype of GALE deficiency

Congenital disorders of glycosylation are a group of rare monogenic inborn errors of metabolism caused by defective glycoprotein and glycolipid glycan synthesis and attachment. Here, we present a patient with galactose epimerase deficiency, also known as GALE deficiency, accompanied by pancytopenia and immune dysregulation. She was first identified by an abnormal newborn screen for galactosemia with subsequent genetic evaluation due to pancytopenia and immune dysregulation. The evaluation ultimately revealed that her known diagnosis of GALE deficiency was the cause of her hematologic and immune abnormalities. These findings further expand the clinical spectrum of disease of congenital disorders of glycosylation.

Inherited thrombocytopenia associated with mutation of UDP-galactose-4-epimerase (GALE)

Severe thrombocytopenia, characterized by dysplastic megakaryocytes and intracranial bleeding, was diagnosed in six individuals from a consanguineous kindred. Three of the individuals were successfully treated by bone marrow transplant. Whole-exome sequencing and homozygosity mapping of multiple family members, coupled with whole-genome sequencing to reveal shared non-coding variants, revealed one potentially functional variant segregating with thrombocytopenia under a recessive model: GALE p.R51W (c.C151T, NM_001127621). The mutation is extremely rare (allele frequency = 2.5 × 10-05), and the likelihood of the observed co-segregation occurring by chance is 1.2 × 10-06. GALE encodes UDP-galactose-4-epimerase, an enzyme of galactose metabolism and glycosylation responsible for two reversible reactions: interconversion of UDP-galactose with UDP-glucose and interconversion of UDP-N-acetylgalactosamine with UDP-N-acetylglucosamine. The mutation alters an amino acid residue that is conserved from yeast to humans. The variant protein has both significantly lower enzymatic activity for both interconversion reactions and highly significant thermal instability. Proper glycosylation is critical to normal hematopoiesis, in particular to megakaryocyte and platelet development, as reflected in the presence of thrombocytopenia in the context of congenital disorders of glycosylation. Mutations in GALE have not previously been associated with thrombocytopenia. Our results suggest that GALE p.R51W is inadequate for normal glycosylation and thereby may impair megakaryocyte and platelet development. If other mutations in GALE are shown to have similar consequences, this gene may be proven to play a critical role in hematopoiesis.

Small-platelet thrombocytopenia in a family with autosomal recessive inheritance pattern

We describe the clinical and laboratory features of a family of Arab ancestry and consanguinity. Five affected individuals were diagnosed in two sibships. All affected members have small platelets, severe to moderate thrombocytopenia of neonatal onset, increased bleeding tendency and bleeding complications such as: life-threatening massive hemoperitoneum due to corpus luteum rupture during ovulation and severe mucosal bleeding. The familial involvement and early onset of the disease support the presence of a congenital genetic disorder with an autosomal recessive inheritance pattern. This does not fit the clinical spectrum of any of the currently known thrombocytopenia disorders.

Spontaneous resolution of extreme thrombocytosis in 2 children

Essential thrombocytosis (ET) is rare in children, sometimes difficult to be distinguished from secondary thrombocytosis. This report concerns 2 children with extreme thrombocytosis of 4100 × 10(9)/L and 1644 × 10(9)/L with partial and complete remission at 3 months and 4 years from diagnosis, with a follow-up of 4 and 17 years, respectively, with no cytoreduction therapy. Diagnosis of ET was suggested according to accepted criteria. However, spontaneous remission of the thrombocytosis argues for the diagnosis of secondary thrombocytosis. These patients highlight the complexity of distinguishing childhood ET from secondary thrombocytosis and the need for cautious personalized decision on cytoreduction therapy.

Transplant outcomes in bone marrow failure syndromes and hemoglobinopathies

Allogeneic hematopoietic stem cell transplantation (HSCT) is the only potential cure for most bone marrow (BM) failure syndromes and hemoglobinopathies. Over the past decade, umbilical cord blood (UCB) has been used more frequently as a stem cell source in patients who lack a suitable BM donor. Although graft failure remains a significant problem, UCB transplantation (UCBT) using the optimal conditioning regimen can be a salvage treatment for patients without a suitable BM donor and warrants evaluation in further prospective studies.

A pedigree with autosomal dominant thrombocytopenia, red cell macrocytosis, and an occurrence of t(12:21) positive pre-B acute lymphoblastic leukemia

Sampling and analyzing new families with inherited blood disorders are major steps contributing to the identification of gene(s) responsible for normal and pathologic hematopoiesis. Familial occurrences of hematological disorders alone, or as part of a syndromic disease, have been reported, and for some the underlying genetic mutation has been identified. Here we describe a new autosomal dominant inherited phenotype of thrombocytopenia and red cell macrocytosis in a four-generation pedigree. Interestingly, in the youngest generation, a 2-year-old boy presenting with these familial features has developed acute lymphoblastic leukemia characterized by a t(12;21) translocation. Tri-lineage involvement of platelets, red cells and white cells may suggest a genetic defect in an early multiliear progenitor or a stem cell. Functional assays in EBV-transformed cell lines revealed a defect in cell proliferation and tubulin dynamics. Two candidate genes, RUNX1 and FOG1, were sequenced but no pathogenic mutation was found. Identification of the underlying genetic defect(s) in this family may help in understanding the complex process of hematopoiesis.

Hematopoietic cell transplantation for congenital bone marrow failure

PURPOSE OF REVIEW

Congenital bone marrow failure is rare and multifactorial. This review focuses on the outcome after allogeneic hematopoietic cell transplantation for the treatment of these disorders, with particular emphasis on recent discoveries and the challenges.

RECENT FINDINGS

In the treatment of congenital bone marrow failure disorders, the goals are to eliminate or reduce early and late toxicities and the risk of graft-versus-host disease. Novel nonmyeloablative fludarabine-based preparative regimens have demonstrated low risks of toxicity and acceptable engraftment rates for several congenital bone marrow failure disorders. Although there seems to be less early toxicity, longer follow-up is needed to determine late effects, especially the development of malignancy. T cell depletion of the bone marrow or peripheral blood, or the use of umbilical cord blood, has decreased the risk of graft-versus-host disease. Together, reduced toxicity and low rates of graft-versus-host disease have at least minimized the morbidity early after transplantation, with promising early survival.

SUMMARY

With marked improvement in rates of survival after allogeneic hematopoietic cell transplantation for selected congenital bone marrow failure disorders, emphasis is now being placed on improving quality of life and reducing late effects. Multicenter collaborative trials will determine the best treatment for these rare disorders.