Variable Clinical Presentation of Shwachman-Diamond Syndrome: Update From the North-American Shwachman-Diamond Syndrome Registry.

Shwachman-Diamond syndrome (SDS) is an autosomal recessively inherited marrow failure syndrome associated with exocrine pancreatic dysfunction and an increased leukemia risk. SDS is caused by biallelic mutations in the SBDS gene. Timely diagnosis prior to the development of life-threatening complications is essential for optimal medical management and outcomes. SDS hematologic complications such as severe marrow failure or leukemia are treated with a hematopoietic stem cell transplant. SDS patients require reduced intensity conditioning regimens to avoid undue regimen-related toxicities, thus the recognition of the underlying diagnosis of SDS is critical. The common constellation of clinical characteristics reported for SDS includes neutropenia, steatorrhea, and failure to thrive.

With the advent of genetic testing, diagnosis is now possible for patients with non-classical presentations of the inherited marrow failure syndromes. The aim of this study was to investigate the range of clinical presentations for SDS with the long-term goal of improving diagnosis.

This study was a retrospective review of medical records obtained by the North American Shwachman-Diamond Syndrome Registry (SDSR) which was founded in 2008. The SDS Registry works in partnership with the Severe Chronic Neutropenia International Registry.

Genetic reports of biallelic SBDS mutations confirming the diagnosis of SDS were available for 31 patients. This SDS study cohort included 19 male and 12 female patients. Median patient age was 10 years with a range of 2 – 49 years. Radiologic reports were available for 23 patients. Pancreatic lipomatosis was noted in 22/23 patients. One patient had an atrophic pancreas without lipomatosis on CT scan at age 6.9 years. Two patients initially had normal early pancreatic studies by CT or ultrasound at ages 1.3 years and 2.6 years, but subsequently were found to have pancreatic lipomatosis by the same imaging modalities later in life. Fecal elastase has not been previously evaluated as a screen for SDS. 14/17 patients (82%) had low fecal elastase levels while 3/17 patients had normal fecal elastase levels. Serum trypsinogen or pancreatic isoamylase were low in all 18 patients tested. 26/31 patients (84%) presented with failure to thrive. 17/31 (54%) patients presented with diarrhea or steatorrhea. 17/31 patients (55%) had congenital anomalies. Neutropenia was the most common hematologic abnormality at presentation (77%). Strikingly, 2 patients presented with isolated thrombocytopenia, 3 patients presented with severe anemia requiring transfusion support, and 5 patients presented without any cytopenias. One patient presented with the initial diagnosis of MDS with a del 20q clone. One patient presented with short stature and a sibling who died from AML. Interestingly, one patient had very short telomeres (<1^st percentile for age) across 3 lymphocyte subsets as well as in total lymphocytes, a pattern typically associated with dyskeratosis congenita.

Data from the North-American Shwachman Diamond Syndrome Registry reveals an unexpected range of clinical presentation for this rare disorder that expands beyond that which is currently classically recognized. The diagnosis of SDS should be considered even in the absence of neutropenia or diarrhea. In our cohort, clues to the underlying diagnosis of SDS included other cytopenias, congenital anomalies, family history, and the del20q clonal marrow abnormality. Reliance on classical clinical descriptions of SDS would miss or delay diagnosis of a significant subset of SDS patients.

Dale:AMGEN: Consultancy.