Shwachman Diamond Syndrome

What is Shwachman Diamond syndrome?

Combining of multiple disorders including bone marrow malfunctioning, skeletal system abnormalities and exocrine pancreatic deficiency due to autosomal recessive disorder is clinically termed as Shwachman Diamond syndrome (SDS). This syndrome is considered as a rare ailment but gained medical attention as it attains the 2nd position among all other inherited pancreatic insufficiency autosomal recessive disorders.

The syndrome name is derived from its inventors, Shwachman, Diamond, et. al., who first reported the syndrome in 1963 at Harvard Medical School^1,2,4.

Symptoms

The four major clinical characteristics of Shwachman Diamond syndrome are as follows:

Exocrine pancreatic insufficiency

The Pancreatic insufficiency provides following symptoms at different stages of life

• Steatorrhoea and malabsorption at the very beginning of the life (in the first month)
• Proper blossom of affected child is failed due poor growth in comparison to normal child
• Fat malabsorption causes vitamins A, D, E and K (fat soluble vitamins) deficiency, but if the child is not suffering from cystic fibrosis, then 40% to 60% of affected individuals gradually improves SDS.
• Abdominal ultrasound or Ct scan provide images of fatty pancreatic infiltration

Haematological

The following are hematological related abnormalities associated with SDS

• Low numbers of CD34+ progenitor cells and a faulty marrow microenvironment
• Neutropenia
• Increased susceptibility towards multiple bacterial infections like pneumonia
• Anaemia
• Thrombocytopenia

Skeletal and growth

Skeletal and growth related abnormalities are as follows

• Most patients with SDS have restricted growth due to malabsorption and also for an inherent abnormality of growth in these patients.
• pubertal delay
• Metaphyseal dysostosis or defective ossification occurs due to skeletal abnormalities. The affected bones are usually in the femoral head, spine, hips and knees
• Rib abnormalities include chostochondral thickening of shortened ribs
• Vitamin D deficiency increase the risk of bone mineralization

Psychological

Certain usual psychological problems associated with SDS in affected children. These problems arise because of neurological disorders

• Learning difficulties
• Mental developmental delay
• Behavioural problems

Other abnormalities

Apart from the above mentioned major health-related abnormalities, some other organ related problems are also included, such as dental defects, dermatological conditions like ichthyosis and severe eczema, myocardial fibrosis, facial deformities, renal calculi and renal tract anomalies^4,6.

Treatment

The aim of the treatment in Shwachman Diamond syndrome are supplementing pancreatic enzyme, preventive measures for invasive or severe infections, early treatment initiation for infectious febrile illness, corrective measures for hematological abnormalities and prevention of orthopedic deformities.

• Pancreatic enzyme supplements need to compensate the pancreatic enzyme deficiency, and this can also slightly improves growth of the affected child.
• Low-fat diet is also recommended for affected patients, as patients unable to metabolize fat completely
• Multivitamin and fat soluble vitamin substitutions require for Shwachman Diamond syndrome affected the individual. All the substitutes amount become decreases with increasing of age.
• At the initial stage of febrile illness in Shwachman Diamond syndrome need bacterial cultures evaluation, because that SDS affected individuals have susceptibility towards sepsis. Early diagnosis and administration of broad-spectrum antibiotics may be beneficial for the patients. Prophylactic antibiotic treatment assists in prevention from infection.
• Yet now no treatment is available for providing complete curing from anemia, neutropenia, or thrombocytopenia.
• Granulocyte colony-stimulating factor (GCSF) may treat neutropenia, but clinical assumption represents, this factor may cause myeloproliferative disorders. In past, Lithium and thiamine were the preferable options of treatment for improving chemotactic performance, but after the discovery of recombinant growth factor in the 1990s, it becomes a favorable treatment choice.
• In the case of symptomatic problems arise due to anemia or thrombocytopenia, then repeated transfusions are an only treatment option, though erythropoietin treatment may provide a beneficial effect in anemic conditions.
• Allogenic hematopoietic stem cell transplantation is the only option to treat myeloproliferative, lymphoproliferative malignancies and aplastic marrow condition, as standard chemotherapy does not provide effective result in the case of Shwachman Diamond syndrome affected patients. Busulfan and cyclophosphamide are examples of chemotherapies can also apply for some cases.
• Shwachman Diamond syndrome affected individuals have normal mesenchymal stem cells and that may successfully manage the hematopoietic stem cell transplantation.
• The initial effect of growth hormone therapy is useful for treating inadequate growth, but prolonged therapy does not effective.
• Metaphyseal dysplasia related deformities can be prevented by pursuing proper orthopedic follow-up measures^2,4.

Life expectancy

Researchers reported that median life expectancy in Shwachman-Diamond syndrome is greater than 35 years of age. The patient who also affected with aplastic anemia due to associated complication can usually survive up to 24 years of age. Shwachman-Diamond syndrome in association with leukemia has much lower median survival age i.e. 10 years of total life span^2,6.

Prognosis

The detail description of Shwachman Diamond syndrome is yet to discover, as the description of this syndrome is relatively new. There is no evidence-based report is available about the prognosis of SDS².

Complications

Different type of bacterial infections like pneumonia, upper respiratory tract infections, otitis media, skin infections, osteomyelitis, sinusitis,  aphthous stomatitis, bacteremia, paronychia etc. are persisted commonly in Shwachman Diamond syndrome affected patients due to neutropenia/neutrophil migration defects.

The possibility of progression of leukemia, myelodysplastic syndrome (MDS), or severe cytopenias is increased with Shwachman Diamond syndrome due to malfunctioning of bone marrow^2,3.

References

1. Shwachman-Diamond syndrome; Genetic Home References; https://ghr.nlm.nih.gov/condition/shwachman-diamond-syndrome
2. Antoinette C Spoto-Cannons, Shwachman-Diamond Syndrome Treatment & Management; Medscape; http://emedicine.medscape.com/article/958476-treatment
3. SHWACHMAN DIAMOND SYNDROME FOUNDATION; HTTP://WWW.SHWACHMAN-DIAMOND.ORG/
4. Shwachman Diamond Syndrome; National Organization For Rare Diseases; https://rarediseases.org/rare-diseases/shwachman-diamond-syndrome/
5. Clinical feature; SDS-Canada; http://www.shwachmandiamondamerica.org/clinical_features.html
6. Shwachman Diamond Syndrome; http://www.webmd.com/children/shwachman-syndrome