Diagnosis

Increased radiotracer activity in a soft tissue mass of the abdomen, is likely due to splenosis in this postsplenectomy patient.

Findings

Anterior and posterior whole-body images following administration of radiotracer are acquired using single photon emission computed tomography/computed tomography (SPECT/CT) and an X-ray of the left shoulder is taken. SPECT/CT images of the abdomen show the liver appears enlarged and demonstrates a homogeneous distribution of radiotracer. The patient is status postsplenectomy with surgical clips noted in the splenic bed. There is a midline soft tissue mass lying midline, anterior to the vertebral column, demonstrating increased radiotracer activity.

Discussion

The function of the liver and spleen have vastly different functions. Nevertheless, phagocytosis is a common function to both. Uptake is performed by the reticuloendothelial cells. In the liver these cells are called Kupffer cells. Technitium 99m-sulfur colloid measures an average of 0.3-1.0µm. Technitium colloid is usually cleared from circulation within minutes—80% to 90% of particles are sequestered by the liver and 5% to 10% to the spleen. This test can be used to identify the relative size and function of the liver and spleen. It is also useful, as in this example, for identifying splenosis.

TAR syndrome is a rare genetic disorder characterized by low platelet level and radial aplasia.

Unlike most other conditions associated with radial aplasia, TAR syndrome patients usually have thumbs. The other bones of the upper limb and shoulder may be absent, hypoplastic, or normal. The lower limbs are less frequently hypoplastic, but may be bowed. Dislocated hips, ankylosis of the knees, valgus and varus deformities of the feet, syndactyly and abnormal toe placement have also been reported.¹ Additional anomalies include congenital heart defects, growth retardation, strabismus, nevus flammeus of forehead, micrognathia, and brachycephaly. The hematologic defects are usually present at birth or appear within the first few months. The inheritance pattern is autosomal recessive.²

Thrombocytopenia, which may be transient, is seen in all cases and will be symptomatic in over 90% of cases within the first four months of life. As age increases, platelet counts typically improve. Nevertheless, removal of the spleen (splenectomy) may be necessary to correct thrombocytopenia caused by platelet destruction and to ultimately increase platelet count. A splenectomy may significantly reduce platelet destruction and increase platelet count by up to 30% because the spleen acts as the primary site of platelet removal and antibody production. The patient above, now an adult, despite splenectomy, remains partially resistant to transfusions, receiving weekly transfusions of platelets.¹

1. Greenhalgh KL, Howell RT, Bottani A, et al. Thrombocytopenia-absent radius syndrome: A clinical genetic study. J Med Genet. 2002;39:876-81.
2. Ward, RE, Bixler D, Provisor AJ, et al. Parent to child transmission of the thrombocytopenia absent radius (TAR) syndrome. Am J Med Genet Suppl. 1986;2:207-14.