Severe congenital neutropenia

Neutrophils are the white blood cells that lead the response to bacterial infection. In severe congenital neutropenia a child is born unable to make enough of them, and the shortage is present from the start rather than arriving later.

The measure used is the absolute neutrophil count. In congenital neutropenia it is usually below 0.5 × 10⁹/L and often below 0.2 — many times lower than a healthy child’s.

The most common single genetic cause is a change in ELANE, and that form is dominant, meaning one altered copy is enough. The same gene also causes a milder relative called cyclic neutropenia, where the count crashes for a few days about every three weeks. They are not the same thing and the infections are more severe in the congenital form.

You may see the name Kostmann syndrome. It comes from a Swedish family described in the 1950s, and the recessive disease in that family is now attributed to a different gene. It is a historical label rather than a synonym for all severe congenital neutropenia.

This is genetically a mixed group — registries count more than a dozen genes under the heading — so any figure labelled “congenital neutropenia” describes that mixture rather than one disease.

Inherited gene changes. The ELANE form is dominant — an affected person has a 50% chance of passing the variant to each child — and some changes arise new in the child rather than being inherited at all. Other genes cause other forms, some of them recessive.

Nothing the parents did causes it. It is also not the same thing as the neutropenia caused by chemotherapy, which is acquired and temporary, or as autoimmune neutropenia — registries keep those as separate categories, and no patient in the autoimmune and idiopathic group developed myeloid leukemia.

Genetic testing is not universal in practice. The US registry notes that financial and insurance barriers limit it, and that the majority of its US patients had not had genetic testing.

Bacterial infection from infancy. Infection of the umbilical stump immediately after birth may be the first sign, followed by recurrent fevers, sinus infections, gum disease, and severe infections in the lungs, liver and soft tissues. Untreated, deep abscesses are common.

Mouth and gum disease is a constant rather than a footnote — ulcers, gingivitis, sore throats, swollen neck glands.

Over the longer term there is a risk of myelodysplastic neoplasms and acute myeloid leukemia. In the US registry it was 76 of 670 patients in the congenital category, against 1 of 266 with cyclic neutropenia and none of 816 with autoimmune or idiopathic disease. The median age at leukemia diagnosis was 16.

The risk appears to rise with cumulative exposure to G-CSF, the growth factor used to treat the condition. Both the French and US registries report that association, and both frame it as something observed in registry data rather than as proven causation. It is a reason for monitoring rather than a reason to fear the treatment.

Death is mostly from infection, and mostly where treatment is absent or failing. In the French registry there were eight deaths from sepsis and none of those eight was receiving G-CSF at the time. In the US registry, infection deaths were attributed to failure to respond to G-CSF, insufficient treatment, or failure to maintain consistent treatment.

The treatment that changed this condition is G-CSF — granulocyte colony-stimulating factor — a growth factor given as an injection under the skin, usually daily, that drives the marrow to produce and release neutrophils. GeneReviews states it improves symptoms and reduces infections in almost everyone affected.

Doses are individualised and are higher in the congenital form than in the cyclic one. In the US registry the median dose in congenital disease was 4.8 micrograms per kilogram per day, and median neutrophil counts rose several-fold on treatment.

Non-response is uncommon but real. In the French registry, G-CSF failed in three of the sixty patients with severe congenital neutropenia who were treated.

A transplant is the exception rather than the rule. GeneReviews describes it as the only alternative for children who do not respond to high-dose G-CSF or who develop a malignant transformation, and the French registry describes it the same way.

The early months can be frightening. Infections in a newborn who cannot fight bacteria escalate quickly, and fever is never a minor event.

Then treatment becomes a daily injection, given at home, indefinitely. For a small child that is a significant thing to build a life around, and for a parent it is a daily act of care that never quite becomes routine.

Mouth and gum problems persist even on treatment for many children, which means regular dental care as a core part of management rather than an extra.

And there is monitoring that does not stop — blood counts, and marrow examinations, watching for a change that most children will never have.

Most children with severe congenital neutropenia never need a donor. G-CSF works for nearly all of them, and a transplant is not the usual treatment. That is the honest headline and it belongs first.

A donor matters for two specific groups: children whose disease does not respond to high-dose G-CSF, and children whose disease transforms into MDS or leukemia. In that second case the transplant is being done for the leukemia rather than for the neutropenia.

When a transplant is needed, match quality and age drove the outcome in the European cohort — significantly better survival with a matched donor, in children under ten, and in more recent years. A matched unrelated donor sat in the same favourable category as a matched sibling, which is a real and supported point about why registries matter.