Shwachman-Diamond syndrome: an inherited, multi-system condition

A rare inherited condition that reaches beyond the marrow

Shwachman-Diamond syndrome, usually shortened to SDS, is an inherited condition that can lead to bone marrow failure.

What sets SDS apart is that it rarely stays in one organ. The pancreas, the bones and the blood-forming marrow are the areas most often affected, and the liver, heart and hormone-producing glands can be involved too. The picture varies widely from one person to the next, which is part of why it can be hard to recognise.

For the wider question of inherited and acquired causes, start with acquired versus inherited bone marrow failure.

What causes Shwachman-Diamond syndrome?

Most cases are linked to changes in a gene called SBDS. MedlinePlus reports that SBDS changes are found in about 90 percent of people with the typical features of SDS. The gene provides instructions for a protein that helps build ribosomes, the structures inside cells that read genetic instructions and make proteins. When too little working SBDS protein is present, researchers suspect ribosome formation suffers. It is still unclear how that produces the main symptoms.

Inheritance is usually autosomal recessive. A child typically receives one altered copy of the gene from each parent, and the parents usually carry one copy each without symptoms of their own. Sometimes a change arises for the first time in the child. Rarely, the condition follows an autosomal dominant pattern. A few other genes are involved in small numbers of cases, and in some people no change is found at all.

How SDS affects the pancreas, blood and bones

Digestion and growth

In most infants with SDS, the pancreas does not make enough digestive enzymes. Food is poorly broken down, so babies often have fatty, foul-smelling stools, fail to gain weight as expected and can become malnourished. The pancreatic problem often improves with age. The GeneReviews chapter on SDS reports that up to half of affected individuals can stop enzyme supplements and absorb fat normally by age four, even when enzyme output stays below normal.

Neutropenia and marrow changes

Most people with SDS have at least occasional episodes of neutropenia, a shortage of neutrophils, the white cells that fight bacteria. That makes pneumonia, ear infections and skin infections more likely. Less often, the red cell count falls, causing anaemia (spelled anemia in US sources), or platelets drop, which can lead to easy bruising and bleeding.

Over time the marrow can change in more serious ways. People with SDS have a higher than average chance of myelodysplastic syndrome (MDS), aplastic anaemia and acute myeloid leukaemia (AML). When red cells alone are affected, the picture is closer to pure red cell aplasia.

Bones and development

Bone changes are common. Problems with bone formation and growth most often affect the hips and knees, and bone density can be low. Some babies are born with a narrow rib cage and short ribs, which can cause serious breathing problems. Alongside these changes, slow growth usually leads to short stature. Some people also have delayed speech and motor development.

How is Shwachman-Diamond syndrome diagnosed?

Most people are diagnosed in infancy or early childhood, after a careful clinical assessment and specialised tests. A NORD summary of the condition notes that there is no single definitive list of diagnostic criteria, so suspicion usually comes from a combination of pancreatic and marrow findings. Genetic testing can confirm the diagnosis by finding disease-causing variants, most often in SBDS. If no genetic cause is identified, experienced clinicians can still make a diagnosis, usually based on pancreatic dysfunction together with bone marrow dysfunction.

Several other tests help narrow things down. When fatty stools occur without chronic breathing problems, doctors often run a sweat test, because cystic fibrosis raises sweat salt levels and SDS does not. A faecal elastase test is the main way to confirm pancreatic insufficiency. To look at the marrow, specialists take a bone marrow aspiration and biopsy, and may use sequencing to follow changing blood cell clones over time.

Some inherited marrow conditions look similar at first. Dyskeratosis congenita also involves marrow failure, but it has abnormally short telomeres and no pancreatic dysfunction. Fanconi anaemia causes marrow failure too, yet it lacks the pancreatic involvement seen in SDS.

Day-to-day care

No treatment corrects the underlying gene change. Care centres on managing symptoms, usually through a team that may include orthopaedic, endocrine, gastroenterology, dental, haematology, nutrition and physiotherapy specialists.

Pancreatic enzyme replacement is taken with meals to help the body digest and absorb fats and other nutrients. Many people also need vitamins A, D, E and K, since fat-soluble vitamins are harder to absorb. Some need a higher-calorie or higher-protein diet to support growth.

Infections call for quick attention. When the neutrophil count stays at or below 500 per cubic millimetre and infections are frequent, a growth factor called G-CSF can be considered. Doctors may also recommend preventive steps and start antibiotics promptly when an infection develops. Because neutropenia raises the risk of dental disease, extra dental care is often part of the plan.

Regular monitoring is the other half of care. The NORD summary suggests a routine like this:

• A complete blood count every 3 to 6 months
• A bone marrow examination every 1 to 3 years, or sooner if needed
• Nutrition and vitamin levels every 6 months
• Bone density testing before and during puberty

These checks exist largely to catch early marrow change, because MDS and AML can develop over time.

Transplant, donors and the question of cure

A stem cell transplant is the only treatment described as curative for the blood-related parts of SDS, according to the NORD summary cited above. It is usually reserved for people with severe marrow failure, MDS or AML rather than offered routinely. The same summary reports survival of about 80 percent when transplant is done for marrow failure, compared with about 49 percent for MDS and 9 percent for AML. Outcomes are much better when transplant happens before cancer develops.

Reduced-intensity regimens are often preferred, because people with SDS tend to be more sensitive to side effects, particularly to the heart and lungs. Donor checks also matter. Relatives who look well can still carry SDS, so potential family donors need testing to rule it out before they are used.

What the outlook looks like

Life expectancy is hard to sum up in one figure, and published numbers describe groups rather than individuals. In a Blood Advances cohort of 153 people with biallelic SBDS variants, median survival was 38.2 years. Of 20 deaths in that group, 17 came from blood-related complications. Also in that cohort, 26 people (17 percent) developed a myeloid malignancy, 16 of them myelodysplasia and 10 acute myeloid leukaemia.

Those figures describe groups, not individuals. A child's own blood counts and marrow results are the more useful guide, so bring those questions to your haematology team.

Families often find support through rare disease organisations. MedlinePlus lists the National Organization for Rare Disorders among its patient support resources for SDS. Bone and growth needs may also call for physical support, and the emotional weight of a rare diagnosis is real for parents and older children alike.

Steady monitoring is what keeps SDS manageable

SDS touches the pancreas, the marrow and the bones at once, so no single check tells the whole story. Enzyme treatment, infection care and marrow surveillance work best when planned together, and consistent follow-up gives the best chance of catching problems early.