Dyskeratosis congenita (DC)

It often starts with a routine blood count. Falling blood counts, large red blood cells (macrocytosis) or a raised level of fetal hemoglobin can lead a blood doctor (hematologist) to look further. A bone marrow test (aspirate and biopsy) shows how well the marrow is making blood and checks the marrow cells for chromosome changes.

The key test measures the length of telomeres, the protective ends of chromosomes, in several kinds of white blood cells. The lab uses a method called flow-FISH and compares the result with people of the same age. Telomeres shorter than the 1st percentile for age point strongly to dyskeratosis congenita or a related telomere disorder. Genetic testing then looks at 16 known genes. It finds the cause in about 8 in 10 people who have the typical features.

The diagnosis can come many years after the first problem, because the classic skin, nail and mouth signs may be missing. In a German group of 42 adults with telomere disorders, the first problem appeared at a median age of 20, but the diagnosis came at a median age of 34. Low blood counts were the most common problem, and liver and lung disease were also frequent. After diagnosis, care teams usually add breathing tests and liver blood tests, and they often HLA-type the patient, brothers and sisters, and parents.

Treatment addresses the manifestations that are present. It may include transfusions, infection care, selected androgen treatment, organ-specific therapy and ongoing cancer surveillance. Medicines that improve blood counts do not amount to correction of the disorder in all tissues.

Allogeneic transplantation is considered for serious or progressive marrow failure or a blood malignancy. Conditioning needs specialist adaptation because organ vulnerability can increase treatment toxicity.

Donor-derived blood production does not prevent every later complication. Lung, liver and cancer surveillance remain necessary, and pre-existing organ disease can limit the safety or expected benefit of transplantation.

When a transplant from a donor is planned, the team usually tests brothers and sisters first. Each full sibling has about a one in four chance of being a full match.

Most patients do not have a matched relative. In the words of NMDP, the U.S. registry, “75% of patients don’t have a fully matched donor in their own family.” The team then searches registries of volunteer donors around the world and banks of donated cord blood. In some transplants, a half-matched parent, child or sibling can also be the donor.

Matching depends on inherited tissue markers called HLA, so a patient is most likely to match someone who shares their ancestry. Every person who joins makes the search a little more likely to succeed, especially for patients from groups that are underrepresented on registries.

Dyskeratosis congenita varies a great deal, even within one family. Some people have nail and skin changes but normal marrow. Others have marrow failure first and the classic signs years later. Severe forms, such as Hoyeraal-Hreidarsson syndrome, begin in early childhood. In a large U.S. study, how the condition was inherited made a clear difference. People with dominant forms (other than TINF2) lived longer than people with recessive, X-linked or TINF2-related forms.

A donor transplant can restore blood production, but it is harder in this condition because the telomere problem also affects other organs. In a study of 94 people, results were better for those under 20 and for those with a matched donor. Survival kept falling over the years: infections caused early deaths, and organ damage and new cancers came later, sometimes a decade after transplant. Experts favor gentler (reduced-intensity) treatment before transplant and a careful check of organ health first.

These numbers describe groups of people followed at specialist centers. They cannot tell any one family what will happen. Regular checks of the blood, lungs, liver, mouth and skin are meant to find problems early.