Fludarabine, cyclophosphamide, and antithymocyte globulin for a patient with dyskeratosis congenita and severe bone marrow failure

Revesz syndrome revisited

Background

Revesz syndrome (RS) is an extremely rare variant of dyskeratosis congenita (DKC) with only anecdotal reports in the literature.

Methods

To further characterize the typical features and natural course of the disease, we screened the English literature and summarized the clinical and epidemiological features of previously published RS cases. In addition, we herein describe the first recorded patient in central Europe.

Results

The literature review included 18 children. Clinical features are summarized, indicating a low prevalence of the classical DKC triad. All patients experienced early bone marrow failure, in most cases within the second year of life (median age 1.5 years; 95% CI 1.4–1.6). Retinopathy occurred typically between 6 and 18 months of age (median age 1.1 years; 95% CI 0.7–1.5). The incidence of seizures was low and was present in an estimated 20% of patients. The onset of seizures was exclusively during early childhood. The Kaplan–Meier estimate of survival was dismal (median survival 6.5 years; 95% CI 3.6–9.4), and none of the patients survived beyond the age of 12 years. Stem cell transplantation (SCT) was performed in eight children, and after a median of 22 months from SCT four of these patients were alive at the last follow up visit.

Conclusion

RS is a severe variant of DKC with early bone marrow failure and retinopathy in all patients. Survival is dismal, but stem cell transplantation may be performed successfully and might improve prognosis in the future.

Allogeneic hematopoietic stem cell transplantation for dyskeratosis congenita

PURPOSE OF REVIEW

Dyskeratosis congenita is an inherited bone marrow failure syndrome caused by defects in telomere maintenance. Hematopoietic stem cell transplantation (HSCT) is the only curative treatment for bone marrow failure because of dyskeratosis congenita. The present review summarizes the literature with respect to the diagnosis and treatment of patients with dyskeratosis congenita who received HSCT, and discusses the recent progress in the management of dyskeratosis congenita.

RECENT FINDINGS

The recent systematic review of the literature showed poor long-term outcome, with 10-year survival estimates of only 23% in 109 patients with dyskeratosis congenita who received HSCT. Multivariate analysis identified age greater than 20 years at HSCT, HSCT before 2000, and alternative donor source to be poor prognostic markers. HSCT for dyskeratosis congenita is characterized by a marked decline in long-term survival because of late deaths from pulmonary complications. However, a prospective study using danazol showed promising results in gain in telomere length and hematologic responses.

SUMMARY

A recent prospective study may support the recommendation that HSCT is not indicated for patients with dyskeratosis congenita; instead, they should receive androgen, particularly danazol, as a first-line therapy. Another option may be routine use of androgen after HSCT for the prophylaxis of pulmonary fibrosis.

A Reduced-Intensity Conditioning Regimen for Patients with Dyskeratosis Congenita Undergoing Hematopoietic Stem Cell Transplantation

Allogeneic hematopoietic stem cell transplantation (HSCT) is the only curative option for progressive marrow failure, myelodysplastic syndrome, or leukemia associated with dyskeratosis congenita (DC). HSCT for DC is limited by a high incidence of treatment-related mortality, thought to be related to underlying chromosomal instability and sensitivity to chemotherapy and radiation. We report our experience in 7 patients with DC who underwent allogeneic transplantation using a reduced-intensity conditioning (RIC) preparative regimen that contained chemotherapy only (no radiation). This RIC regimen, designed specifically for patients with DC, contained alemtuzumab, fludarabine, and melphalan (with melphalan at 50% reduced dosing), with the goal of decreasing toxicity and improving outcome. All 7 patients engrafted, with none developing mixed chimerism or rejection. Two patients experienced acute graft-versus-host disease (GVHD) and 1 went on to develop limited chronic GVHD of the skin. Five patients remain alive and well at a median follow-up of 44 months (range, 14 to 57 months). We conclude that a radiation-free RIC regimen results in durable engraftment, acceptable toxicity, and improved overall survival in patients with DC undergoing allogeneic HSCT.

Successful T-cell-depleted haploidentical hematopoietic stem cell transplantation in a child with dyskeratosis congenita after a fludarabine-based conditioning regimen

Allogeneic hematopoietic stem cell transplantation (HSCT) is the only cure for marrow failure associated with dyskeratosis congenita (DC). Data on transplants from alternative donors are limited. We describe a boy with DC and severe aplastic anemia who underwent haploidentical T-cell depleted HSCT using a reduced-intensity conditioning regimen. He underwent engraftment without toxicity or GVHD. His posttransplant course was complicated by EBV reactivation, treated with rituximab and EBV-specific T lymphocytes. After 26 months, he is in complete chimerism, with normal blood count and no sign of GVHD or pulmonary dysfunction. To the best of our knowledge, this is the first report of DC successfully treated with allogeneic HSCT from a haploidentical family donor.

Diffuse hemorrhagic colitis in a patient with dyskeratosis congenita after nonmyeloablative allogeneic hematopoietic stem cell transplantation

Dyskeratosis congenita (DC) is a rare inherited disorder characterized by reticular skin pigmentation, oral cavity leukoplakia, and nail dystrophy. Bone marrow failure in DC can only be cured by allogeneic hematopoietic stem cell transplantation (HSCT). After a nonmyeloablative, matched unrelated donor transplant, the 21-year-old patient experienced severe lower gastrointestinal tract hemorrhage caused by diffuse colitis. The etiology remained unclear. Diffuse colitis with life-threatening hemorrhage has now been reported in 3 DC patients after unrelated allogeneic HSCT. To identify the underlying causes and the disease-specific risks, and to allow for prevention and/or optimal management, data should be prospectively collected.

Zinsser-Cole-Engmann syndrome: A rare case report with literature review

Zinsser-Cole-Engmann syndrome, more commonly known as Dyskeratosis Congenita, is a heritable genodermatosis having an estimated incidence of 1 in 1 million people. It is important for an oral physician to be aware of this condition as oral leukoplakia occurs in this condition as part of a classic triad along with reticulate skin pigmentation and nail dystrophy. Besides these, there may be myriad multisystem involvement as well. These individuals have a high predilection for developing malignancies as well as other grave life-threatening conditions. Timely diagnosis and management of these cases may help improve their morbidity and mortality, for which oral physicians can play a major role in recognizing the cases. This will only be possible when more of such cases are reported in dental literature. Here we present a case report of a 30 year old male patient who reported to our department with all the characteristic features of the triad and a few additional findings concordant to the disease as well.

Key words:Zinsser-Cole-Engmann syndrome, Dyskeratosis Congenita, leukoplakia, genodermatosis, skin pigmentation, nail dystrophy, progeria, hematological disturbances.

Human telomeres and telomere biology disorders

Telomeres consist of long nucleotide repeats and a protein complex at chromosome ends essential for chromosome stability. Telomeres shorten with each cell division and thus are markers of cellular age. Dyskeratosis congenita (DC) is a cancer-prone inherited bone marrow failure syndrome caused by germ-line mutations in key telomere biology genes that result in extremely short telomeres. The triad of nail dysplasia, abnormal skin pigmentation, and oral leukoplakia is diagnostic of DC but highly variable. Patients with DC may also have but numerous other medical problems, including pulmonary fibrosis, liver abnormalities, avascular necrosis of the hips, and stenosis of the esophagus, lacrimal ducts, and/or urethra. All modes of inheritance have been reported in DC and de novo mutations are common. Broad phenotypic heterogeneity occurs within DC. Clinically severe variants of DC are Hoyeraal-Hreidarsson syndrome and Revesz syndrome. Coats plus syndrome joined the spectrum of DC with the discovery that it is caused by mutations in a telomere-capping gene. Less clinically severe variants, such as subsets of apparently isolated aplastic anemia or pulmonary fibrosis, have also been recognized. These patients may not have the DC-associated mucocutaneous triad or complicated medical features, but they do have the same underlying genetic etiology. This has led to the use of the descriptive term telomere biology disorder (TBD). This chapter will review the connection between telomere biology and human disease through the examples of DC and its related TBDs.

Updates on the biology and management of dyskeratosis congenita and related telomere biology disorders

Dyskeratosis congenita (DC) is a cancer-prone inherited bone marrow failure syndrome caused by aberrant telomere biology. The mucocutaneous triad of nail dysplasia, abnormal skin pigmentation and oral leukoplakia is diagnostic, but is not always present; DC can also be diagnosed by the presence of very short leukocyte telomeres. Patients with DC are at high risk of bone marrow failure, pulmonary fibrosis, liver disease, cancer and other medical problems. Germline mutations in one of nine genes associated with telomere maintenance are present in approximately 60% of patients. DC is one among the group of clinically and biologically related telomere biology disorders, including Hoyeraal-Hreidarsson syndrome, Revesz syndrome, Coats plus (also known as cranioretinal microangiopathy with calcifications and cysts) and subsets of aplastic anemia, pulmonary fibrosis, nonalcoholic and noninfectious liver disease and leukemia. The authors review the pathobiology that connects DC and the related telomere biology disorders, methods of diagnosis and management modalities.

Disease-specific hematopoietic cell transplantation: nonmyeloablative conditioning regimen for dyskeratosis congenita

Dyskeratosis congenita (DC) is characterized by reticular skin pigmentation, oral leukoplakia and abnormal nails. Patients with DC have very short telomeres and approximately one-half have mutations in telomere biology genes. A majority of patients with DC develop BM failure (BMF). Hematopoietic cell transplantation (HCT) represents the only known cure for BMF in DC, but poses significant toxicities. We report six patients who underwent allogeneic HCT with a novel nonmyeloablative conditioning regimen specifically designed for DC patients. Graft sources included related PBSCs (1), unrelated BM (2) and unrelated double umbilical cord blood (3). Complete donor engraftment was achieved in five of six patients. One patient had initial autologous hematopoietic recovery, which was followed by a second transplant that resulted in 88% donor chimerism. With a median follow-up of 26.5 months, four patients are alive, three of whom were recipients of unrelated grafts. We conclude with this small study that encouraging short-term survival can be achieved with HCT in patients with DC using a preparative regimen designed to promote donor engraftment and minimize life-threatening disease-specific complications such as pulmonary fibrosis. Long-term follow-up will be crucial with respect to individualized patient care with each of the transplanted individuals.

Bone marrow transplantation for inherited bone marrow failure syndromes

The inherited bone marrow failure (BMF) syndromes are characterized by impaired hematopoiesis and cancer predisposition. Most inherited BMF syndromes are also associated with a range of congenital anomalies. Progress in improving the outcomes for children with inherited BMF syndromes has been limited by the rarity of these disorders, as well as disease-specific genetic, molecular, cellular, and clinical characteristics that increase the risks of complications associated with hematopoietic stem cell transplantation (HSCT). As a result, the ability to develop innovative transplant approaches to circumvent these problems has been limited. Recent progress has been made, as best evidenced in studies adding fludarabine to the preparative regimen for children undergoing unrelated donor HSCT for Fanconi anemia. The rarity of these diseases coupled with the far more likely incremental improvements that will result from ongoing research will require prospective international clinical trials to improve the outcome for these children.

Advances in the understanding of dyskeratosis congenita

Dyskeratosis congenita (DC) is a rare inherited syndrome exhibiting marked clinical and genetic heterogeneity. It is characterised by mucocutaneous abnormalities, bone marrow failure and a predisposition to cancer. Bone marrow failure is the principal cause of premature mortality. Studies over the last 10 years have demonstrated that DC is principally a disease of defective telomere maintenance. All DC patients have very short telomeres and the genetically characterised cases of DC have mutations in six genes which either encode components of the telomerase complex (DKC1, TERC, TERT, NOP10, NHP2) or shelterin (TINF2); these are important in the elongation and protection of the telomeric end, respectively. These advances have led to the recognition of cryptic forms of DC, such as presentations with aplastic anaemia and myelodysplasia. They have also increased our understanding of normal haematopoiesis and provided new insights to the aetiology of some cases of aplastic anaemia and related haematological disorders.

Dyskeratosis congenita

Dyskeratosis congenita (DC) is an inherited bone marrow failure syndrome characterized clinically by the triad of abnormal nails, reticular skin pigmentation, and oral leukoplakia, and is associated with high risk of developing aplastic anemia, myelodysplastic syndrome, leukemia, and solid tumors. Patients have very short germline telomeres, and approximately half have mutations in one of six genes encoding proteins that maintain telomere function. Accurate diagnosis of DC is critical to ensure proper clinical management, because patients who have DC and bone marrow failure do not respond to immunosuppressive therapy and may have increased morbidity and mortality associated with hematopoietic stem cell transplantation.

TINF2, a component of the shelterin telomere protection complex, is mutated in dyskeratosis congenita

Patients with dyskeratosis congenita (DC), a heterogeneous inherited bone marrow failure syndrome, have abnormalities in telomere biology, including very short telomeres and germline mutations in DKC1, TERC, TERT, or NOP10, but approximately 60% of DC patients lack an identifiable mutation. With the very short telomere phenotype and a highly penetrant, rare disease model, a linkage scan was performed on a family with autosomal-dominant DC and no mutations in DKCI, TERC, or TERT. Evidence favoring linkage was found at 2p24 and 14q11.2, and this led to the identification of TINF2 (14q11.2) mutations, K280E, in the proband and her five affected relatives and TINF2 R282H in three additional unrelated DC probands, including one with Revesz syndrome; a fifth DC proband had a R282S mutation. TINF2 mutations were not present in unaffected relatives, DC probands with mutations in DKC1, TERC, or TERT or 298 control subjects. We demonstrate that a fifth gene, TINF2, is mutated in classical DC and, for the first time, in Revesz syndrome. This represents the first shelterin complex mutation linked to human disease and confirms the role of very short telomeres as a diagnostic test for DC.

The role of telomere biology in bone marrow failure and other disorders

Telomeres, consisting of nucleotide repeats and a protein complex at chromosome ends, are essential in maintaining chromosomal integrity. Dyskeratosis congenita (DC) is the inherited bone marrow failure syndrome (IBMFS) that epitomizes the effects of abnormal telomere biology. Patients with DC have extremely short telomere lengths (<1st percentile) and many have mutations in telomere biology genes. Interpretation of telomere length in other IBMFSs is less straightforward. Abnormal telomere shortening has been reported in patients with apparently acquired hematologic disorders, including aplastic anemia, myeolodysplasia, paroxysmal nocturnal hemoglobinuria, and leukemia. In these disorders, the shortest-lived cells have the shortest telomeres, suggestive of increased hematopoietic stress. Telomeres are also markers of replicative and/or oxidative stress in other complex disease pathways, such as inflammation, stress, and carcinogenesis. The spectrum of related disorders caused by mutations in telomere biology genes extends beyond classical DC to include marrow failure that does not respond to immunosuppression, idiopathic pulmonary fibrosis, and possibly other syndromes. We suggest that such patients be categorized as having an inherited disorder of telomere biology. Longitudinal studies of patients with very short telomeres but without classical DC are necessary to further understand the long-term sequelae, such as malignancy, osteonecrosis/osteoporosis, and pulmonary and liver disease.