Shwachman-Diamond syndrome

It is an inherited multi-system disorder rather than a cancer, and the classic combination is three things at once: a pancreas that does not make enough digestive enzymes, low blood counts, and differences in the growing skeleton.

It usually announces itself through the gut rather than the blood. Fatty, bulky, foul-smelling stools and a baby not gaining weight. Many children are investigated for malabsorption long before anyone looks closely at a blood count — in one review of 156 published patients, first symptoms came at a median of about two months and the diagnosis at a median of 15 months.

The part of the pancreas involved is the exocrine part, which makes digestive enzymes and sends them into the gut. The part that makes insulin is a different job in the same organ and is not the problem here.

It belongs to the inherited bone marrow failure syndromes, alongside Fanconi anemia, dyskeratosis congenita and Diamond-Blackfan anemia. It is also what is called a ribosomopathy: ribosomes are the machines every cell uses to build proteins, and the fault here is in assembling them — which is why one gene can disturb the pancreas, the bones and the marrow at the same time.

In around 90% of people, two altered copies of a gene called SBDS, inherited one from each parent. Both copies have to be affected before the condition appears, so a person with one changed copy is a carrier and is not ill. Across more than 200 families, no aplastic anemia has been observed in carriers — parents do not have the disease.

About one in ten of these gene changes arises new in the child rather than being inherited, so an absent family history does not rule it out.

A few rarer genes account for under 1% each, and one of them behaves differently: SRP54 is dominant, meaning one altered copy is enough, which changes the inheritance conversation for a family entirely. The rare-gene forms are also not clinically identical to the classic picture.

The mechanism is worth a moment. A working ribosome is built from two subunits that must lock together, and a blocking protein has to be prised off one of them first. The SBDS protein is what does the prising. Without that step, mature ribosomes are in short supply — and because that is general protein-making machinery rather than one blood protein, several fast-turnover tissues suffer at once.

The pancreas problem affects more than 90% of people. Without digestive enzymes reaching the gut, fat and the fat-soluble vitamins A, D, E and K are not absorbed, which produces malabsorption, poor nutrition and growth failure.

One counter-intuitive thing worth knowing: pancreatic function is not fixed. Up to half of people can stop enzyme supplements and absorb fat normally by around age four, even though their enzyme secretion remains below normal.

In the blood, a low neutrophil count is what shows up first in almost every affected child, and low counts of some kind affect more than 95% of people. Infection risk is not only a numbers problem — the neutrophils that are present are also worse at migrating to where an infection is.

Around 60% have skeletal differences, and roughly half of children sit below the third percentile for both height and weight. A minority develop a narrow, rigid rib cage that restricts breathing.

Around 20% of children show intellectual disability in at least one area, and attention difficulties are more common than in the general population — which is why formal neuropsychological screening is built into the care schedule rather than being an afterthought.

And the reason surveillance never stops: the risk of myelodysplastic neoplasms and acute myeloid leukemia continues across life rather than plateauing in childhood. Some people are found to already have MDS or leukemia on their very first marrow biopsy.

The pancreas is managed with enzyme capsules taken with meals and supplements of the fat-soluble vitamins, with blood levels checked twice a year to see whether it is working. Some children come off enzymes around age four — a clinical decision made on testing rather than something a family stops on its own.

Infections are treated promptly. A growth factor called G-CSF, which pushes the marrow to release more neutrophils, may be considered where the count stays very low with severe recurrent infections, though there is caution about prolonged use.

Surveillance is the backbone of care rather than an optional extra: blood counts every three to six months, a marrow examination with chromosome studies every one to three years indefinitely, liver enzymes annually, bone imaging during rapid growth, bone density around puberty, and developmental and neuropsychological assessment at set ages through childhood.

A transplant is not routine treatment here. GeneReviews is explicit that the marrow abnormalities are not treated with a transplant unless there is severe aplasia, myelodysplastic change, or transformation to leukemia.

Conditioning intensity is genuinely unsettled rather than solved. The 2022 EBMT consensus recommends reduced-intensity regimens to lower transplant-related mortality — but the US registry data showed 5-year survival of 78% with full-intensity conditioning against 71% with reduced-intensity, a difference that was not statistically significant. Both readings belong on the page.

There is no approved therapy directed at the underlying genetic defect. A transplant addresses the blood system only.

There is usually a long diagnostic runway. For many families that means a year or more of unexplained diarrhoea, fatty stools and a baby who will not grow, before anyone names it.

Because the presenting problem is feeding and growth, parents often arrive at a haematology conversation from a gastroenterology starting point. Being told this is a bone marrow failure syndrome can land as a complete surprise.

The daily burden is enzyme capsules with every meal and snack, vitamin supplements, weighing and measuring, and dietitian appointments.

Then a lifetime of marrow examinations. The recommended surveillance is a biopsy every one to three years, indefinitely — a recurring, invasive procedure that exists specifically to catch a change early. Unlike conditions with a defined endpoint, this continues into adult life because the risk does.

Learning support is a mainstream part of care here rather than a footnote, and about half of children are visibly smaller than their peers.

A transplant is not the usual treatment for Shwachman-Diamond syndrome, and most people with it never need a donor. The 2022 EBMT consensus estimates that 10% to 20% need a transplant, and it is reserved for severe marrow failure, myelodysplastic change, or leukemia.

The absolute numbers make the point better than any argument could. EBMT centres across Europe reported 74 transplants for this condition over 28 years. The US registry captured 52 over 17 years.

When a donor is needed, though, unrelated donors carried most of the load in Europe — 68% of those 74, against 24% from siblings and 8% from a parent. Bone marrow rather than blood was the dominant graft source, which differs from many adult indications.

One reason for that unrelated share is specific to inherited conditions and worth stating: a sibling who appears perfectly healthy may themselves have Shwachman-Diamond syndrome, so any potential related donor has to be evaluated for it first. Note the distinction — carriers with one altered copy are unaffected and are not the problem; it is an affected sibling that has to be excluded. In the US cohort, only about half of the marrow-failure patients had been genetically tested at all.