A Comparative Molecular Dynamics Study of Selected Point Mutations in the Shwachman–Bodian–Diamond Syndrome Protein SBDS

Lethal Complications and Complex Genotypes in Shwachman Diamond Syndrome: Report of a Family with Recurrent Neonatal Deaths and a Case-Based Brief Review of the Literature

Shwachman Diamond Syndrome (SDS) is a multi-system disease characterized by exocrine pancreatic insufficiency with malabsorption, infantile neutropenia and aplastic anemia. Life-threatening complications include progression to acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS), critical deep-tissue infections and asphyxiating thoracic dystrophy. In most patients, SDS results from biallelic pathogenic variants in the SBDS gene, different combinations of which contribute to heterogenous clinical presentations. Null variants are not well tolerated, supporting the theory that the loss of SBDS expression is likely lethal in both mice and humans. A novel complex genotype (SBDS:c.[242C>G;258+2T>C];[460-1G>A]/WFS1:c.[2327A>T];[1371G>T]) was detected in a family with recurrent neonatal deaths. A female neonate died three hours after birth with hemolytic anemia, and a male neonate with severe anemia, thrombocytopenia and neutropenia succumbed on day 40 after Staphylococcus epidermidis infection. A subsequent review of the literature focused on fatal complications, complex SBDS genotypes and/or unusual clinical presentations and disclosed rare cases, of which some had unexpected combinations of genetic and clinical findings. The impact of pathogenic variants and associated phenotypes is discussed in the context of data sharing towards expanding scientific expert networks, consolidating knowledge and advancing an understanding of novel underlying genotypes and complex phenotypes, facilitating informed clinical decisions and disease management.

Two mutations in the SBDS gene reveal a diagnosis of Shwachman-Diamond syndrome in a patient with atypical symptoms

We present the case of a 53-yr-old woman with an inherited bone marrow failure coexisting with uncommon extrahematological symptoms, such as cirrhosis and skin abnormalities. Whole-exome sequencing revealed a diagnosis of Shwachman-Diamond syndrome (SDS) with an atypical presentation. Unexpected was the age of disease expression, normally around the pediatric age, with a predominantly median survival age of 36 yr. To our knowledge, she was the first adult patient with a molecular diagnosis of Shwachman-Diamond in Uruguay. The patient was referred to our service when she was 43-yr-old with a history of bone marrow failure with anemia and thrombocytopenia. All secondary causes of pancytopenia were excluded. Bone marrow aspirate and biopsy specimens were hypocellular for the patient's age. Numerous dysplastic features were observed in the three lineages. She had a normal karyotype and normal chromosomal fragility. A diagnosis of low-risk hypoplastic MDS was made. Dermatological examination revealed reticulate skin pigmentation with hypopigmented macules involving the face, neck, and extremities; nail dystrophy; premature graying; and thin hair. Extrahematological manifestations were present (e.g., learning difficulties, short stature). Last, she was diagnosed with cryptogenic liver cirrhosis CHILD C. This rules out all other possible causes of chronic liver disease. This clinical presentation initially oriented the diagnosis toward telomeropathy, so we did a telomeropathy NGS panel that came up negative. Finally, we did an exome sequencing that confirmed the diagnosis of SDS. Using whole-exome sequencing, we were able to find two compound heterozygous mutations in the SBDS gene that were responsible for the phenotype of a patient that was undiagnosed for 10 years. An earlier genetic diagnosis could have influenced our patient's outcome.