A case of Shwachman Diamond syndrome in a young female with acute lymphoblastic leukemia

A 16-year-old girl with fever and right axillary swelling, for which she underwent an ultrasound examination (US) in another hospital, came to our observation. The US showed a voluminous hypoechoic and partially colliquated lymph node, without visibility of the hilum and with poor vascular signal to the evaluation with color-Doppler, which required further diagnostic investigation.

The ultrasound examination of the superficial lymph nodes stations carried out at our hospital, confirmed the suspicion of neoplastic infiltration of the right axillary lymph node, while the US examination of the abdomen did not show any lesions to the internal organs but only the hyperechogenicity of the pancreas (Figure 1). The blood tests performed showed an altered blood count due to mild normocytic normochromic anaemia, thrombocytopenia, neutropenia, lymphocytosis, and reduction of pancreatic amylase and lipase. Besides, a biopsy of the suspected lymph node and a bone marrow needle aspiration was executed, the latter showing a 56% blast infiltration, so a diagnosis of acute lymphoblastic leukaemia (ALL) was made. The total body CT examination performed to stage the disease confirmed the absence of further lesions and the presence of a hypodense pancreas (Figure 2). 

The evidence of adipose infiltration of the pancreas should not lead directly to consider SDS as the first hypothesis rather than more common conditions such as cystic fibrosis or Cushing syndrome. Therefore, deep research into the patient's medical history was performed, reporting a mild failure to thrive, intermittent neutropenia, and episodes of pancreatic insufficiency. Thus, the patient underwent an x-ray of the left hand to evaluate the bone age according to Greulich and Pyle method, which confirmed the growth retardation (Figure 3).

Clinical data together with imaging findings, and subsequent genetic analyses led to the diagnosis of Schwachman-Diamond syndrome.

Schwachman-Diamond syndrome (SDS) is an autosomal recessive multisystem disease caused by mutations in the SBDS (Shwachman-Bodian-Diamond syndrome) gene located on chromosome 7q11ed and is the second most common cause of exocrine pancreatic insufficiency after cystic fibrosis in children. It is a rare syndrome with an estimated incidence of approximately 1 in 76,000 [1]. SDS has a heterogeneous clinical presentation. The syndrome usually occurs with exocrine pancreatic insufficiency, intermittent neutropenia, and skeletal abnormalities such as metaphyseal chondrodysplasia. In addition, other organs may be affected, such as brain [2], liver and kidneys; impairment of the immune system and, rarely, growth hormone deficiency or diabetes [3,4] can also occur. Moreover, SDS is associated with a predisposition to the development of myelodysplasia syndrome (MDS) or acute leukaemia, in particular acute myeloid leukaemia (AML) [5]. It has been reported that children with SDS develop AML in 12-25% of cases, while cases of SDS and ALL rarely occur [6]. However, the most common clinical presentation of SDS consists of the triad: exocrine pancreatic dysfunction, skeletal abnormalities and bone marrow failure [7].
In our case, after the diagnosis of ALL, the girl underwent the US of the abdomen and the hyperechogenicity of the pancreatic parenchyma was incidentally found. Ultrasound is the first imaging modality used for the staging of children with leukaemia as it is a non-invasive diagnostic method, does not involve exposure to ionizing radiation and allows to evaluate any secondary leukemic infiltrations affecting the abdominal organs. The scarce presence of subcutaneous adipose tissue and the reduced thickness of abdominal structures in children, make ultrasound very useful in assessing the size and structure of the pancreas. In patients with SDS, the US accurately demonstrates the hyperechogenicity of the pancreatic parenchyma, suggestive of adipose replacement. The second level imaging method for the evaluation of the pancreas is magnetic resonance (MRI), which offers greater sensitivity and specificity than ultrasound for the detection of intrapancreatic fat.  In fact, in addition to the conventional T1 and T2 weighted sequences, the T1 sequences with saturation of the adipose signal provide an excellent demonstration of pancreatic tissue and its adipose infiltration [8]. In our case, the girl was not subjected to MRI because she underwent a total body CT to stage leukaemia. CT revealed widespread hypodensity of the pancreatic parenchyma with negative Hounsfield coefficients.

In conclusion, SDS is a rare multisystem disease with considerable phenotypic variability and clinical presentation. In our case, the radiological examinations used in the management of the little patient with ALL have allowed advancing the suspicion of the presence of a genetic disease, thanks to the accidental finding of adipose infiltration of the pancreas. Ultimately, making an early diagnosis is crucial as SDS is related to an increased risk of infections, haematological dysfunctions and malignancies.

Written informed patient consent for publication has been obtained.