Thyroid disease in children and adolescents with PTEN hamartoma tumor syndrome (PHTS).

Patients with PTEN hamartoma tumor syndrome (PHTS) are at increased risk of developing benign and malignant tumors, including thyroid carcinoma. Benign thyroid lesions and single cases of thyroid carcinoma have been reported in children with PHTS. We conducted a retrospective, single-centered study including children and adolescents with a molecularly proven diagnosis of PTEN. Our cohort consists of 16 patients, with a mean age at diagnosis PHTS of 5.7 years. Twelve of 16 cases exhibited thyroid abnormalities (75%). In seven patients, thyroid abnormalities were already present at first ultrasound screening, in five cases they occurred during follow-up. Eight patients underwent thyroidectomy. Histopathology included nodular goiter, follicular adenoma, papillary microcarcinoma in a boy of six and follicular carcinoma in a girl of 13 years. Two patients had autoimmune thyroid disease. CONCLUSION: Thyroid disease is common in children with PHTS. Physicians caring for patients with early thyroid abnormalities and additional syndromal features should be aware of PHTS as a potentially underlying disorder. Ultrasound screening should be performed immediately after diagnosis of PHTS and repeated yearly or more frequently. Because of possible early cancer development, we recommend early surgical intervention in the form of total thyroidectomy in cases of suspicious ultrasound findings. What is Known: • PHTS patients are at high risk of developing benign and malignant tumors. • Individual cases of thyroid carcinoma in children have been reported. What is New: • Thyroid disease is even more common in children with PHTS (75%) than previously expected. • Frequently thyroid disease is the first organ pathology requiring diagnostic workup and therefore children with PHTS should be examined for thyroid disease right after diagnosis and receive follow-up on a regular basis throughout life.

Immune dysregulation in patients with PTEN hamartoma tumor syndrome: Analysis of FOXP3 regulatory T cells.

BACKGROUND: Patients with heterozygous germline mutations in phosphatase and tensin homolog deleted on chromosome 10 (PTEN) experience autoimmunity and lymphoid hyperplasia. OBJECTIVES: Because regulation of the phosphoinositide 3-kinase (PI3K) pathway is critical for maintaining regulatory T (Treg) cell functions, we investigate Treg cells in patients with heterozygous germline PTEN mutations (PTEN hamartoma tumor syndrome [PHTS]). METHODS: Patients with PHTS were assessed for immunologic conditions, lymphocyte subsets, forkhead box P3 (FOXP3)+ Treg cell levels, and phenotype. To determine the functional importance of phosphatases that control the PI3K pathway, we assessed Treg cell induction in vitro, mitochondrial depolarization, and recruitment of PTEN to the immunologic synapse. RESULTS: Autoimmunity and peripheral lymphoid hyperplasia were found in 43% of 79 patients with PHTS. Immune dysregulation in patients with PHTS included lymphopenia, CD4+ T-cell reduction, and changes in T- and B-cell subsets. Although total CD4+FOXP3+ Treg cell numbers are reduced, frequencies are maintained in the blood and intestine. Despite pathogenic PTEN mutations, the FOXP3+ T cells are phenotypically normal. We show that the phosphatase PH domain leucine-rich repeat protein phosphatase (PHLPP) downstream of PTEN is highly expressed in normal human Treg cells and provides complementary phosphatase activity. PHLPP is indispensable for the differentiation of induced Treg cells in vitro and Treg cell mitochondrial fitness. PTEN and PHLPP form a phosphatase network that is polarized at the immunologic synapse. CONCLUSION: Heterozygous loss of function of PTEN in human subjects has a significant effect on T- and B-cell immunity. Assembly of the PTEN-PHLPP phosphatase network allows coordinated phosphatase activities at the site of T-cell receptor activation, which is important for limiting PI3K hyperactivation in Treg cells despite PTEN haploinsufficiency.

Autoimmunity, intestinal lymphoid hyperplasia, and defects in mucosal B-cell homeostasis in patients with PTEN hamartoma tumor syndrome.

The Phosphatase And Tensin Homolog Deleted On Chromosome 10 (PTEN) regulates the phosphoinositol-3-kinase (PI3K)-AKT signaling pathway. In a series of 34 patients with PTEN mutations, we described gastrointestinal lymphoid hyperplasia, extensive hyperplastic tonsils, thymus hyperplasia, autoimmune lymphocytic thyroiditis, autoimmune hemolytic anemia, and colitis. Functional analysis of the gastrointestinal mucosa-associated lymphoid tissue revealed increased signaling via the PI3K-AKT pathway, including phosphorylation of S6 and increased cell proliferation, but also reduced apoptosis of CD20(+)CD10(+) B cells. Reduced activity of PTEN therefore affects homeostasis of human germinal center B cells by increasing PI3K-AKT signaling via mammalian target of rapamycin as well as antiapoptotic signals.