Visceral adipose tissue differences in black and white women.

Fat distribution and metabolic variables were studied in 8 black and 10 white age- and weight-matched obese women undergoing a 6-mo weight-reducing regimen. Fat patterning was determined by using anthropometry and computed tomography to quantitate total, subcutaneous, and visceral adipose tissue (VAT) areas at the L2-L3 and L4-L5 levels of the lumbar spine, before, during, and after a modified fast. Black women had smaller depots of VAT than white women at both the L2-L3 (P = 0.004) and L4-L5 (P = 0.054) sites. Differences persisted after an average 17.2-kg weight loss. Although waist-hip ratio was similar in both groups, black women had 23% less VAT than white women (P = 0.007). Black women had significantly lower plasma glucose (P = 0.031) and triglycerides (P = 0.006) with significantly higher plasma high-density-lipoprotein concentrations (P < 0.001). Data from this study suggest that racial differences exist in VAT and metabolic risk factors for obesity-related illness.

Pulmonary function and high-resolution CT findings in patients with an inherited form of pulmonary fibrosis, Hermansky-Pudlak syndrome, due to mutations in HPS-1.

OBJECTIVE: To describe and correlate pulmonary function and high-resolution CT (HRCT) scan scores in individuals with a high risk for development of pulmonary fibrosis, ie, Hermansky-Pudlak syndrome (HPS) patients with mutations in the HPS-1 gene. DESIGN: Cross-sectional analysis of consecutive, eligible patients. PATIENTS: Thirty-eight HPS inpatients at the National Institutes of Health Clinical Center with HPS-1 mutations. RESULTS: Thirty-seven patients were Puerto Rican and exhibited the typical 16-base pair (bp) duplication in exon 15 of HPS-1. One non-Puerto Rican was homozygous for a different mutation (intervening sequence 17 -2 A-->C) previously reported in the HPS-1 gene; he died at age 35 of pulmonary insufficiency. For the 23 patients who had pulmonary symptoms, the mean age of onset was 35 years. For all 38 patients (mean age, 37 +/- 2 years), the mean FVC was 71% of predicted; the mean FEV(1), 76%; mean total lung capacity (TLC), 72%; mean vital capacity (VC), 68%; and mean diffusing capacity of the lung for carbon monoxide (DLCO), 72%. When patients were grouped according to the extent of their reduction in FVC, the other four pulmonary function parameters followed the FVC. Seventeen patients had abnormal chest radiographs, and 31 (82%) had abnormal HRCT scans of the chest, for which a scoring system of 0 (normal) to 3 (severe fibrosis) is presented. The mean +/- SEM HRCT score for 38 patients was 1.30 +/- 0.17. HRCT scores correlated inversely with FVC and DLCO. CONCLUSIONS: Mutations in the HPS-1 gene, whether or not they involve the typical 16-bp duplication seen in Puerto Rican patients, are associated with fatal pulmonary fibrosis. In affected patients, the FVC, FEV(1), TLC, VC, and DLCO fall in concert, and this functional deficit correlates with HRCT scan evidence of progression of interstitial lung disease.

Pulmonary dysfunction in adults with nephropathic cystinosis.

OBJECTIVE: To characterize the pulmonary dysfunction in patients with nephropathic cystinosis after renal transplantation. DESIGN: Cross-sectional analysis of consecutive adult patients. PATIENTS: Twelve adult, nephropathic cystinosis patients and 3 adult, ocular, nonnephropathic cystinosis patients admitted to the National Institutes of Health Clinical Center. RESULTS: The 12 nephropathic cystinosis patients (age range, 21 to 40 years) showed an extraparenchymal pattern of restrictive lung disease, with inspiratory and expiratory dysfunction. Specifically, the mean FVC was 58% of predicted, the mean FEV(1) was 57% of predicted, and the mean total lung capacity was 66% of predicted, while the mean residual volume was normal. Furthermore, the mean maximal inspiratory pressure for the eight patients tested was 40% of predicted, and the mean maximal expiratory pressure was 26% of predicted. Two patients died of respiratory insufficiency. All the patients had lived at least 17 years, while lacking compliant cystine-depleting therapy with oral cysteamine. Seven patients had a conical chest, restricting excursion, and 10 of the 12 patients had evidence of the myopathy that typifies late cystinosis. In fact, the severity of pulmonary disease correlated directly with the severity of myopathy in our group of 12 patients. In contrast, the lung parenchyma was essentially normal, as gauged by chest radiographs and CT scans of the lung. The three patients with nonnephropathic cystinosis displayed entirely normal pulmonary function. CONCLUSION: The distal myopathy characteristic of nephropathic cystinosis results in an extraparenchymal pattern of restrictive lung disease in adults who have not received long-term cystine depletion. Whether or not oral cysteamine therapy can prevent this complication remains to be determined.

Comprehensive evaluation of 35 patients with lymphangioleiomyomatosis.

OBJECTIVES: To evaluate comprehensively the characteristics of lymphangioleiomyomatosis (LAM), with emphasis on the application of imaging and immunohistochemical methods. DESIGN: Prospective study. PATIENTS: Thirty-five female subjects with LAM. SETTING: Clinical Center, National Institutes of Health. INTERVENTIONS: BAL, pulmonary function test, ventilation/perfusion lung scans, CT of the chest and abdomen, ultrasonography of abdomen, and immunohistochemical study of lung biopsy specimens. RESULTS: Most patients had exertional dyspnea (83%) and pneumothorax (69%). BAL did not show diagnostic changes. The most common abnormalities on pulmonary function tests were decreased diffusing capacity of carbon monoxide (83%), hypoxemia (57%), and airway obstruction (51%). Bronchodilator response was found in 26% of patients. CT, which is almost pathognomonic, showed numerous thin-walled cysts throughout both lungs in all patients. Thirty-four patients (97%) had abnormal ventilation and/or perfusion lung scans. An unusual "speckling" pattern was observed on ventilation scans of 74% of patients. Common extrapulmonary features were retroperitoneal adenopathy (77%) and renal angiomyolipomas (60%). The percentage of abnormal smooth muscle cells (LAM cells), reactive with HMB45, varied from 17 to 67% in 10 lung biopsy specimens. CONCLUSIONS: Improved diagnostic methods have defined the abnormalities in patients with pulmonary LAM and increased the potential for early recognition and treatment of this disorder. Patients with LAM should be evaluated for bronchodilator responsiveness and may benefit from a trial of bronchodilators.

Fine needle aspiration of the pancreas. A five-year experience.

Forty fine needle aspiration (FNA) biopsies of the pancreas were performed on 37 patients with a radiologic suspicion of malignancy; 32 aspirations were guided by ultrasound, 2 were guided by CT, and 6 were obtained intraoperatively. A pathologist read a rapid-stained smear of the initial aspirate as the procedure was performed and triaged specimens for routine cytologic, cell block and ultrastructural study in solid lesions plus carcinoembryonic antigen (CEA) assay and amylase study in cystic lesions. Purulent material was studied by gram staining and culture. The overall sensitivity in the series was 81%, with a specificity of 100%. No complications were noted. Ultrastructural examination improved the diagnostic accuracy in two cases. Assays for CEA and amylase in "cyst fluids" differentiated true cysts and cystadenocarcinoma from pseudocysts. Maximum utilization of the material aspirated was useful in diagnosing the etiology of solid and cystic pancreatic masses.

Fine needle aspiration of the liver.

A total of 81 transhepatic fine needle aspiration (FNA) biopsies were performed on 78 patients to rule out focal or diffuse neoplastic disease; 87.6% were performed with ultrasound guidance, 6.1% with CT guidance, 3.7% intraoperatively and 1 using fluoroscopy during percutaneous transhepatic cholangiography. Smears of the aspirated samples were cytologically evaluated with clinical and radiologic correlation; in addition, histologic examination of cell blocks was performed in 46% of the cases, ultrastructural examination in 34% of the cases and peroxidase-antiperoxidase staining in 3 cases. Ultrastructural definition of the type of malignancy was possible in 24 cases (29%). Minor complications in two patients were pain and tenderness at the puncture site. The sensitivity for malignancy was 91%, the specificity was 100%, the predictive value of positive results was 100%, and the predictive value of negative results was 73%. This series demonstrates that FNA biopsy with ultrasound guidance can provide an accurate diagnosis of malignancy and may preempt a lengthy workup in the search for a primary tumor.

Lymphangioleiomyomatosis (LAM): a review of clinical and morphological features.

A review is presented of the clinical and morphological manifestations of lymphangioleiomyomatosis (LAM), a systemic disorder of unknown etiology that affects women. The clinical features include dyspnea, hemoptysis, recurrent pneumothorax, chylothorax, and chylous ascites. It is characterized by: 1) proliferation of abnormal smooth muscle cells (LAM cells) in pulmonary interstitium and along the axial lymphatics of the thorax and abdomen; 2) thin-walled pulmonary cysts, and 3) a high incidence of angiomyolipomas. The pulmonary cystic lesions have a characteristic appearance on high resolution computed tomography. The most specific method for diagnosing LAM is lung biopsy to demonstrate the presence of LAM cells, either by their characteristic histological appearance or by specific immunostaining with HMB-45 antibody. LAM cells differ in several important respects from the types of smooth muscle cells normally present in lung. Their reactivity with HMB-45 antibody is localized in stage I and stage II melanosomes. LAM cells show additional evidence of incomplete melanogenesis, and the significance of these observations remains to be determined. Two types of LAM cells are recognized: 1) small, spindle-shaped cells that are centrally located in the LAM nodules and are highly immunoreactive for matrix metalloproteinase-2 (MMP-2), its activating enzyme (MT-1-MMP), and proliferating cell nuclear antigen (PCNA), and 2) large, epithelioid cells that are distributed along the periphery of the nodules and show a high degree of immunoreactivity with HMB-45 antibody and with antibodies against estrogen and progesterone receptors. Types of treatment used for LAM include oophorectomy, administration of Lupron or progesterone and in very severe cases, pulmonary transplantation (following the onset of respiratory insufficiency, not relieved by O(2)).

Nephrocalcinosis in homozygous familial hypercholesterolemia: ultrasound and CT findings.

An association between homozygous familial hypercholesterolemia (FH) and nephrocalcinosis has not, to our knowledge, been previously reported. Evaluation in 10 cases of homozygous FH revealed evidence of nephrocalcinosis in 7 cases. Fine, uniform calcifications in the renal papillae were demonstrated by renal ultrasound or CT. Renal papillary necrosis was demonstrated by intravenous pyelogram in one case. No renal function impairment was noted in these seven patients. There was no evidence of hypercalcemia. These findings may have implications for the use of a potentially nephrotoxic drug for the treatment of this disease--in particular, when an immunosuppressive agent is required following liver transplantation.

Testicular adrenal rest tissue in congenital adrenal hyperplasia: comparison of MR imaging and sonographic findings.

OBJECTIVE: The purpose of our study was to describe the MR features of testicular adrenal rest tissue in patients with congenital adrenal hyperplasia and to compare the usefulness of MR imaging with that of sonography for the detection of testicular adrenal rest tissue. SUBJECTS AND METHODS: Nineteen patients with congenital adrenal hyperplasia underwent MR imaging and gray-scale and color Doppler sonography of the testicles during the same visit to our institution. Findings were compared. RESULTS: MR features of testicular adrenal rest tissue included the following: isointensity (71% of the masses) and slight hyperintensity (29% of the masses) relative to normal testicular tissue on T1-weighted images; hypointensity relative to normal testicular tissue on T2-weighted images (100% of the masses); and diffuse enhancement on contrast-enhanced T1-weighted images (85% of the masses). MR imaging and sonography revealed the testicular lesions equally well. Eleven (58%) of 19 patients had normal findings on MR imaging and sonography. Eight (42%) of 19 patients had 14 intratesticular masses detected by both imaging techniques. CONCLUSION: MR imaging and sonography are equally useful in the detection of testicular adrenal rest tissue. Because sonography is more accessible to most institutions and is less expensive, it is the imaging technique of choice for the detection of testicular adrenal rest tissue.

Lymphangioleiomyomatosis: abdominopelvic CT and US findings.

PURPOSE: To describe the abdominal computed tomographic (CT) and ultrasonographic (US) findings in patients with thoracic lymphangioleiomyomatosis (LAM) and to relate the prevalence of the findings to the severity of pulmonary disease. MATERIALS AND METHODS: Eighty patients with LAM underwent chest and abdominopelvic CT and abdominopelvic US. The images were reviewed prospectively by one radiologist, and the abdominal findings were recorded and correlated with the severity of pulmonary disease at thin-section CT. RESULTS: Sixty-one (76%) of 80 patients had positive abdominal findings. The most common abdominal findings included renal angiomyolipoma (AML) in 43 patients (54%), enlarged abdominal lymph nodes in 31 (39%), and lymphangiomyoma in 13 (16%). Less common findings included ascites in eight (10%), dilatation of the thoracic duct in seven (9%), and hepatic AML in three (4%). A significant correlation (P =.02) was observed between enlarged abdominal lymph nodes and increased severity of lung disease. CONCLUSION: There are characteristic abdominal findings in patients with LAM that, in conjunction with the classic thin-section CT finding of pulmonary cysts, are useful in establishing this diagnosis.

Lymphangioleiomyomatosis: CT of diurnal variation of lymphangioleiomyomas.

PURPOSE: To evaluate the imaging and clinical features of lymphangioleiomyomas and to describe the phenomenon of diurnal variation in the size of lymphangioleiomyomas in patients with lymphangioleiomyomatosis. MATERIALS AND METHODS: One hundred twenty-eight patients with lymphangioleiomyomatosis underwent chest and abdominopelvic computed tomography (CT). Thirteen patients underwent CT in the morning and afternoon of the same day to assess diurnal variation in lymphangioleiomyoma size. RESULTS: Twenty-seven of 128 patients (21%) had 54 lymphangioleiomyomas. The vast majority (96%) of these masses contained material of low attenuation at CT. Associated CT findings included enlarged abdominal lymph nodes, pleural effusions, ascites, and dilatation of the thoracic duct. The prevalence of lymphangioleiomyomas was 15% in patients who had mild pulmonary disease, 19% in patients who had moderate disease, and 26% in patients who had severe disease. Diurnal variation in size of masses was demonstrated in 12 of 13 patients. Seven of the 27 patients who had masses underwent biopsy; all seven were confirmed to have lymphangioleiomyomas. The most common symptoms associated with lymphangioleiomyomas were bloating, abdominal pain, and edema of the lower extremities. The majority of the patients reported worsening of symptoms as the day progressed. CONCLUSION: Lymphangioleiomyomas are common in patients with lymphangioleiomyomatosis. Diurnal variation in size may explain worsening of symptoms during the day.

Systemic mastocytosis: CT and US features of abdominal manifestations.

PURPOSE: To study the imaging findings in patients with systemic mastocytosis and to correlate the findings with the severity of disease on the basis of an established classification system. Pathologic findings, when available, were correlated with imaging findings. MATERIALS AND METHODS: Computed tomographic (CT) and ultrasound (US) scans and corresponding pathologic findings, when available, were retrospectively reviewed in 27 patients with systemic mastocytosis. RESULTS: Only five (19%) of the patients in our series had normal abdominal CT and/or US examination results. Common abdominal imaging findings associated with systemic mastocytosis were hepatosplenomegaly, retroperitoneal adenopathy, periportal adenopathy, mesenteric adenopathy, thickening of the omentum and the mesentery, and ascites. Less common findings included hepatofugal portal venous flow, Budd-Chiari syndrome, cavernous transformation of the portal vein, ovarian mass, and complications such as chloroma. The findings were more common in patients with category II and those with category III disease. CONCLUSION: Abdominal findings at CT and US are common in patients with systemic mastocytosis. Although the findings in patients with systemic mastocytosis are not specific to the disease, they are useful in directing further studies for diagnostic confirmation and in estimating the extent of systemic involvement.

Cerebellar and spinal hemangioblastomas: evaluation with intraoperative gray-scale color Doppler flow US.

Intraoperative gray-scale and color Doppler flow ultrasound (US) studies were performed in 12 patients with von Hippel-Lindau disease during surgical excision of hemangioblastomas. There were a total of 21 lesions: two were in the cerebellum and 19 were in the spinal cord. Twelve of the 19 spinal hemangioblastomas were hyperechoic to the spinal cord and thus were easily detected with gray-scale US. Color Doppler flow images provided improved delineation of all lesions compared with the images produced with standard gray-scale US. Seven of the 19 spinal lesions were detected only with color Doppler flow imaging because they were isoechoic to the normal spinal cord at gray-scale US. Color Doppler flow imaging enabled differentiation of the cysts and syrinx cavities associated with hemangioblastomas from dilated intraspinal vascular structures. In all cases, intraoperative color Doppler flow imaging facilitated the localization of hemangioblastomas during the neurosurgical procedure.

Mastocytosis: magnetic resonance imaging patterns of marrow disease.

OBJECTIVE: To report the bone marrow MRI findings of patients with mastocytosis and correlate them with clinical, pathologic, and radiographic features. DESIGN AND PATIENTS: Eighteen patients with mastocytosis had T1-weighted spin echo and short tau inversion recovery MRI of the pelvis at 0.5 T. In each patient the MR pattern of marrow disease was classified according to intensity and uniformity and was correlated with the clinical category of mastocytosis, bone marrow biopsy results, and radiographic findings. RESULTS: Two patients had normal MRI scans and normal bone marrow biopsies. One patient had a normal MRI scan and a marrow biopsy consistent with mastocytosis. Fifteen patients had abnormal MRI scans and abnormal marrow biopsies. There were several different MR patterns of marrow involvement; none was specifically associated with any given clinical category of mastocytosis. Fifteen of the 18 patients had radiographs of the pelvis; of those, 13 with abnormal MRI scans and abnormal marrow biopsies had the following radiographic findings: normal (nine); sclerosis (three); diffuse osteopenia (one). CONCLUSION: While radiographs are very insensitive for the detection of marrow abnormalities in mastocytosis, MRI is very sensitive and may display several different patterns of marrow involvement.

Multilocular thymic cysts: imaging features in children with human immunodeficiency virus infection.

PURPOSE: To evaluate the radiologic and follow-up features of multilocular thymic cysts in children with human immunodeficiency virus (HIV) infection. MATERIALS AND METHODS: Four HIV-infected children with large anterior mediastinal masses depicted at routine chest radiography underwent ultrasonography (US), unenhanced and contrast material-enhanced computed tomography (CT), and unenhanced and gadolinium-enhanced MR imaging of the chest. Gallium scanning was also performed in three of the four children. The patients underwent follow-up radiologic examinations for 8-15 months. RESULTS: The multiloculated nature of the masses was depicted at contrast-enhanced but not unenhanced CT. Similarly, the septations were depicted on T2-weighted, short inversion time inversion-recovery (STIR), and contrast-enhanced T1-weighted, MR images but not on the unenhanced T1-weighted images. US scans depicted the septations within each mass, but findings were technically limited because only portions of each mass were depicted. Gallium scans in three masses depicted uptake of radionuclide in two and no uptake in one. Surgical biopsy was performed in each mass: Follicular hyperplasia and diffuse plasmacytosis of the thymus were found but not evidence of neoplastic or infectious origin. At follow-up, the mass decreased in volume in two patients, did not change in one patient, and increased in volume in one patient. CONCLUSION: HIV-infected patients with asymptomatic mediastinal masses depicted at routine chest radiography should undergo contrast-enhanced CT. If a solid mass is depicted, biopsy should be performed to exclude neoplastic or infectious origins. If a multiloculated anterior mediastinal mass is depicted, symptomatic follow-up is adequate since the finding represents a rare multilocular thymic cyst that does not have negative clinical implications.

Testicular adrenal rest tissue in congenital adrenal hyperplasia: findings at Gray-scale and color Doppler US.

PURPOSE: To study the ultrasound (US) features of scrotal adrenal rest tissue in congenital adrenal hyperplasia (CAH). MATERIALS AND METHODS: Gray-scale and color Doppler US examinations were performed of scrotal masses in eight patients. The masses were evaluated for size, location, echogenicity, sound attenuation, and vascularity. RESULTS: Seventeen intratesticular masses and one extratesticular mass were examined. All were hypoechoic except for one intratesticular mass that contained hyperechoic areas. Six masses demonstrated sound attenuation. The mediastinum testis was found in the center of 11 of the 17 intratesticular masses. At color Doppler US, six masses were hypervascular, seven were isovascular, and five were hypovascular relative to the normal testicle. All intratesticular masses contained vascular structures that entered them from the normal testis without change in course or caliber. Eleven masses showed a spoke-like pattern of converging vessels. CONCLUSION: The US features of scrotal adrenal rests assist diagnosis of CAH.

Sonography of gallbladder abnormalities in acromegaly patients following octreotide and ursodiol therapy: incidence and time course.

PURPOSE: We studied the effects of octreotide and ursodiol on the gallbladders of patients with acromegaly. METHODS: We performed gallbladder sonography in patients with acromegaly at various intervals during treatment. Group I (18 patients) was treated with subcutaneous injections of the somatostatin analogue octreotide. Group II (10 patients) was treated with ursodiol while receiving octreotide therapy. RESULTS: Seventy-eight percent of patients receiving octreotide developed gallbladder abnormalities: sludge in 72% (13/18) and calculi in 39% (7/18). Ursodiol reversed the gallbladder abnormalities in 7 of 10 patients. CONCLUSIONS: A majority of patients receiving octreotide develop gallbladder abnormalities. Ursodiol appears to reverse the abnormalities in most cases.

Testicular adrenal rest tissue in congenital adrenal hyperplasia: serial sonographic and clinical findings.

OBJECTIVE: The purpose of this study was to describe the serial sonographic findings and clinical and laboratory data obtained during follow-up of patients with congenital adrenal hyperplasia in whom testicular adrenal rest tissue develops. MATERIALS AND METHODS: We retrospectively reviewed testicular sonography and laboratory data for 12 patients with congenital adrenal hyperplasia who also had intratesticular masses consistent with adrenal rest tissue. The studies were done during follow-up that ranged from 7 months to 10 years. RESULTS: During follow-up of 11 of the 12 patients after the initial sonographic diagnosis, the testicular adrenal rest tissue either remained stable in size (n = 1), grew larger or smaller (n = 9), disappeared (n = 4), or reappeared after disappearing (n = 3). In one patient, the testicular adrenal rest tissue grew very rapidly in a 1-month interval. Discordant changes in the testicular adrenal rest tissue were noted in 10 patients with bilateral masses. We found no relationship between the change in size of the masses and clinical control (based on 17-hydroxyprogesterone level) at the time of sonography. CONCLUSION: In patients with congenital adrenal hyperplasia who have testicular masses detected sonographically, testicular adrenal rest tissue is the most likely diagnosis. Testicular adrenal rest tissue may remain stable in size, grow larger or smaller, or disappear during sonographic follow-up. The change in size may be marked, may occur very rapidly, and, in our study cohort, was not related to short-term clinical control based on 17-hydroxyprogesterone level at the time of sonography.

Pulmonary lymphangioleiomyomatosis: correlation of ventilation-perfusion scintigraphy, chest radiography, and CT with pulmonary function tests.

PURPOSE: To determine the findings on ventilation-perfusion (V-P) scintigrams, computed tomographic (CT) scans, and chest radiographs and correlate them with pulmonary function test results in patients with lymphangioleiomyomatosis. MATERIALS AND METHODS: V-P scintigraphy, chest radiography, conventional and thin-section CT, and pulmonary function tests were performed in 39 patients. The images were graded on a scale of 0 (normal) to 3 (severely abnormal). RESULTS: Imaging abnormalities were found on 92% of ventilation scintigrams, 92% of perfusion scintigrams, 79% of chest radiographs, 100% of CT scans, and 100% of thin-section CT scans. On ventilation scintigrams, 28 (72%) patients demonstrated a speckling pattern. On CT scans, all patients had pulmonary cysts. Univariate analysis showed that extent of disease on chest radiographs and CT scans, cyst size, V-P abnormalities, and degree of speckling were inversely correlated with forced expiratory volume in one second (FEV(1)), diffusing capacity of lung for carbon monoxide, and the ratio of FEV(1) to forced vital capacity (FVC) (P <.01) but not with FVC and total lung capacity. Larger cyst size correlated with extent of disease at CT, but not significantly (P =.056). CONCLUSION: Scintigraphic and radiologic abnormalities are seen in a majority of patients with lymphangioleiomyomatosis. On ventilation scintigrams, a frequently seen speckling pattern may be related to accumulation of radionuclide in pulmonary cysts-a hallmark of the disease at CT. Findings with each imaging modality correlate with certain pulmonary functions.

Multilocular thymic cysts in children with human immunodeficiency virus infection: clinical and pathologic aspects.

BACKGROUND: Children with human immunodeficiency virus (HIV) infection have an increased susceptibility to severe and unusual infections, malignancies, and disorders characterized by abnormal lymphoproliferation (e.g., lymphoid interstitial pneumonitis). We report a novel disease entity associated with pediatric HIV infection that is characterized by massive enlargement of the thymus as a result of lymphoid hyperplasia and multicystic changes. METHODS: Eight patients with HIV infection and cystic enlargement of the thymus are subject of this report. The status of their HIV disease and its clinical and radiologic manifestations at the time of diagnosis of the mediastinal mass are described. Tissue specimens were obtained from six patients and examined by microscopy and immunohistochemistry. The specimens were also evaluated for the evidence of HIV and Epstein-Barr virus by in situ hybridization. RESULTS: Patients were between 2.1 and 12.1 years of age, with CD4+ cell counts between 102 and 733 cells/mm3. In all eight cases an anterior mediastinal mass was discovered incidentally on radiography of the chest, and computed tomography of the chest revealed a multicystic appearance. Histologic examination demonstrated distortion of the thymic architecture by focal cystic changes, lymphoid follicular hyperplasia, diffuse plasmacytosis, and multinucleated giant cells. In situ hybridization revealed HIV particles on the surface of follicular dendritic cells. Further, results of in situ hybridization for EBV were positive in lymphoid cells from biopsy samples of four patients. The patients were followed between 8 months and 4.8 years. In five patients the mass either decreased in size or resolved completely. CONCLUSIONS: We describe a series of children with HIV infection and multilocular thymic cysts. We hypothesize that aberrant immunoregulation in these HIV-infected children leads to follicular hyperplasia and multicystic changes in the thymus, causing massive enlargement. EBV infection might also contribute to the pathogenesis of this process. Because none of our patients had symptoms from the mass, and there was no evidence of malignancy in the examined biopsy samples, it seems prudent to manage such children with careful follow-up examinations.