Cytogenetic abnormalities in dyskeratosis congenita--report of five cases

Fanconi anemia and dyskeratosis congenita/telomere biology disorders: Two inherited bone marrow failure syndromes with genomic instability

Inherited bone marrow failure syndromes (IBMFS) are a complex and heterogeneous group of genetic diseases. To date, at least 13 IBMFS have been characterized. Their pathophysiology is associated with germline pathogenic variants in genes that affect hematopoiesis. A couple of these diseases also have genomic instability, Fanconi anemia due to DNA damage repair deficiency and dyskeratosis congenita/telomere biology disorders as a result of an alteration in telomere maintenance. Patients can have extramedullary manifestations, including cancer and functional or structural physical abnormalities. Furthermore, the phenotypic spectrum varies from cryptic features to patients with significantly evident manifestations. These diseases require a high index of suspicion and should be considered in any patient with abnormal hematopoiesis, even if extramedullary manifestations are not evident. This review describes the disrupted cellular processes that lead to the affected maintenance of the genome structure, contrasting the dysmorphological and oncological phenotypes of Fanconi anemia and dyskeratosis congenita/telomere biology disorders. Through a dysmorphological analysis, we describe the phenotypic features that allow to make the differential diagnosis and the early identification of patients, even before the onset of hematological or oncological manifestations. From the oncological perspective, we analyzed the spectrum and risks of cancers in patients and carriers.

Dyskeratosis congenita: a literature review

Dyskeratosis congenita is a rare hereditary disease that occurs predominantly in males and manifests clinically as the classic triad of reticulate hyperpigmentation, nail dystrophy and leukoplakia. It increases the risk of malignancy and other potentially lethal complications such as bone marrow failure, lung and liver diseases. Mutations in 19 genes are associated with dyskeratosis congenita, and a fifth of the pathogenic mutations are found in DKC1, the gene coding for dyskerin. This review aims to address the clinical and genetic aspects of the disease.

Dyskeratosis Congenita: a historical perspective

"Dyskeratosis Congenita (DC) also known as Zinsser-Engman-Cole syndrome is a rare multi-system bone marrow failure syndrome characterised by mucocutaneous abnormalities and an increased predisposition to cancer". This is a common definition of DC but how did this definition arise? The aim of this review is to follow the development of DC and associated diseases from its first reported description in the early 20th century to the current understanding of the genes involved and its pathophysiology in 2007 in a chronological order. Although this review is not intended to be an exhaustive citation of the literature available it does provide a summary of the key developments, citing particularly the earlier reports of each development.

Reticulate hyperpigmentation

Disorders that are characterized by a reticulate pattern of pigmentation are reviewed. Dyskeratosis congenita (DKC) is the prototype of these. In addition to reticulate hyperpigmentation, mucosal leukoplakia, bone marrow dysfunction, cytogenetic instability, and a predisposition to malignancy are characteristic of DKC. The most common pattern of inheritance is X-linked, with heterozygous females showing variable expression, most likely depending on tissue-specific patterns of random X-inactivation. Other reticulate pigmentary disorders reviewed include the Naegeli-Franceschetti-Jadassohn syndrome, X-linked reticulate pigmentary disorder, dermatopathia pigmentosa reticularis, Dowling-Degos disease, dyschromatosis, confluent and reticulated papillomatosis of Gougerot and Carteaud, reticulate acropigmentation of Kitamura, and Revescz syndrome. Diagnosis, treatment, and sometimes genetic counseling remain problematic for these entities. The pathophysiology of these disorders is unknown, but will certainly be aided greatly by the future identification of the underlying genes.

Dyskeratosis congenita is a chromosomal instability disorder

Dyskeratosis congenita (DC) is a rare inherited disorder characterized by dystrophic changes in the skin and mucous membranes, bone marrow failure, and a predisposition to malignancy. In the majority of families the pattern of inheritance of DC has been compatible with X-linkage, the most likely location being Xq28. The primary defect responsible for this disease remains unknown. As DC shares many features (congenital abnormalities, bone marrow failure) with the chromosomal instability disorder. Fanconi's anaemia (FA), several studies have focused on cytogenetic features in DC. Unlike in FA, cytogenetic studies on peripheral blood lymphocytes have shown no significant difference between DC and normal lymphocytes with or without prior incubation with clastogens (bleomycin, diepoxybutane, mitomycin-c, 4-nitroquinoline-1-oxide). However, studies on DC fibroblasts have shown abnormalities in both morphology (polygonal cell shape, ballooning, dendritic-like projections) and growth rate (doubling time about twice normal), as well as numerous unbalanced chromosomal rearrangements (dicentrics, tricentrics, translocations) in the absence of any clastogenic agents. Bone marrow metaphases from one out of three patients studied (the eldest of the three) also showed unbalanced chromosomal rearrangements in the absence of any clastogens. Cell-specific difference and a higher rate of chromosomal rearrangements in the older patients appear to correlate with the clinical evolution of the disease. These findings suggest that the DC defect predisposes DC cells to developing chromosomal rearrangements.

Treatment of the hematological manifestations of dyskeratosis congenita

Dyskeratosis congenita is a congenital multisystem disorder, characterized by skin pigmentation, dystrophic nails, and leukoplakia. Hematologic abnormalities progressing to severe pancytopenia play a significant role in the poor prognosis of afflicted patients. We report on a patient with dyskeratosis congenita and severe aplastic anemia, complicated by life threatening infection. The patient was treated with recombinant granulocyte-macrophage colony-stimulating factor. This therapy resulted in a moderate and transient improvement in absolute neutrophil counts. Current concepts regarding the pathogenesis and etiology of dyskeratosis congenita are discussed, while reviewing the available therapeutic options.

Oral-dental findings in dyskeratosis congenita

A 13-yr-old girl with dyskeratosis congenita is presented. Besides oral leukoplakia and nail dystrophies, there was evidence of pancytopenia, growth retardation, alopecia, mental retardation and microcephaly. The oral findings included caries, gingival recession, short-blunted roots, gingival bleeding, tooth mobility and severe alveolar bone loss resembling juvenile periodontitis.

Cytogenetic studies of skin fibroblast cultures from a karyotypically normal female with dyskeratosis congenita

Skin fibroblast cultures from a female patient with dyskeratosis congenita revealed markedly increased frequencies of chromosomal breaks, hypodiploidy, and premature centromere disjunction. The frequencies of mitotic disturbances, like ana- and telophase bridges, lagging chromosomes, and micronuclei were almost as dramatically elevated as in cultures from two severely affected patients with Fanconi anemia. Provided that our patient is representative for an autosomal form of dyskeratosis congenita, this type of the disease seems to be characterized by chromosomal instability with a characteristic pattern of cytogenetic abnormalities.

Dyskeratosis congenita (Zinsser-Cole-Engman syndrome). An autopsy case presenting with rectal carcinoma, non-cirrhotic portal hypertension, and Pneumocystis carinii pneumonia

A 24-year-old Japanese man presented with dyskeratosis congenita (DC, Zinsser-Cole-Engman syndrome) complicated by non-cirrhotic portal hypertension, signet ring carcinoma of the rectum and Pneumocystis carinii pneumonia. At the age of 9 years, he was diagnosed as having DC on the basis of typical clinical manifestations including atrophic lingual papillae, hyperpigmentation of the skin, thrombocytopenia, and ophthalmological abnormalities. A few years later pancytopenia and splenomegaly developed. At 24 years, signet ring carcinoma of the rectum was detected but could not be resected because of the severity of the pancytopenia. Death was due to respiratory failure from P. carinii pneumonia. At autopsy the case illustrated several unique findings for DC, including non-cirrhotic portal hypertension, atrophy of frontal lobe and markedly slender folia of the cerebellum and superimposed infections with herpes zoster virus and P. carinii. Striking lymphocyte depletion and atrophy of lymphoid parenchyma in lymph nodes, tonsils, spleen, gastrointestinal tract, or thymus were seen histologically. The morphological picture supports the suggestion that there is a defect in the cell-mediated immune system in patients with DC, although immunoglobulin levels in the blood are normal. The cell-immune deficiency is a major factor in the poor prognosis.