Hector Mesa

Mouse Model of X-Linked Alport Syndrome

X-linked Alport syndrome (XLAS) is a progressive disorder of basement membranes caused by mutations in the COL4A5 gene, encoding the alpha5 chain of type IV collagen. A mouse model of this disorder was generated by targeting a human nonsense mutation, G5X, to the mouse Col4a5 gene. As predicted for a nonsense mutation, hemizygous mutant male mice are null and heterozygous carrier female mice are mosaic for alpha5(IV) chain expression. Mutant male mice and carrier female mice are viable through reproductive age and fertile. Mutant male mice died spontaneously at 6 to 34 wk of age, and carrier female mice died at 8 to 45 wk of age, manifesting proteinuria, azotemia, and progressive and manifold histologic abnormalities of the kidney glomerulus and tubulointerstitium. Ultrastructural abnormalities of the glomerular basement membrane, including lamellation and splitting, were characteristic of human XLAS. The mouse model described here recapitulates essential clinical and pathologic findings of human XLAS. With alpha5(IV) expression reflecting X-inactivation patterns, it will be especially useful in studying determinants of disease variability in the carrier state.

X-inactivation modifies disease severity in female carriers of murine X-linked Alport syndrome

BACKGROUND Female carriers of X-linked Alport syndrome (XLAS) demonstrate variability in clinical phenotype that, unlike males, cannot be correlated with genotype. X-inactivation, the method by which females (XX) silence transcription from one X chromosome in order to achieve gene dosage parity with males (XY), likely modifies the carrier phenotype, but this hypothesis has not been tested directly. METHODS Using a genetically defined mouse model of XLAS, we generated two groups of Alport female (Col4a5(+/-)) carriers that differed only in the X-controlling element (Xce) allele regulating X-inactivation. We followed the groups as far as 6 months of age comparing survival and surrogate outcome measures of urine protein and plasma urea nitrogen. RESULTS Preferential inactivation of the mutant Col4a5 gene improved survival and surrogate outcome measures of urine protein and plasma urea nitrogen. In studies of surviving mice, we found that X-inactivation in kidney, measured by allele-specific mRNA expression assays, correlated with surrogate outcomes. CONCLUSIONS Our findings establish X-inactivation as a major modifier of the carrier phenotype in X-linked Alport syndrome. Thus, X-inactivation patterns may offer prognostic information and point to possible treatment strategies for symptomatic carriers.

Rapid and complete resolution of chemotherapy-induced thrombotic thrombocytopenic purpura/hemolytic uremic syndrome (TTP/HUS) with rituximab

PurposeGemcitabine-induced thrombocytopenic purpura/hemolytic uremic syndrome (TTP/HUS) is a well described, albeit rare, complication, which is associated with a high morbidity and mortality. Treatment with standard TTP/HUS therapies such as plasma exchange, and cessation of gemcitabine is often unsuccessful. The purpose of this report is to describe the successful treatment of gemcitabine-induced TTP/HUS with rituximab, a CD20 monoclonal antibody that has been used for the treatment of refractory idiopathic TTP/HUS.MethodsWe describe the clinical course and follow-up of a patient who developed gemcitabine-induced TTP/HUS, did not respond to cessation of gemcitabine, administration of plasma exchanges, and intravenous glucocorticoids, but responded to rituximab.ResultsTTP/HUS responded rapidly and resolved completely with two courses (8 doses) of intravenous rituximab. In three of four reported cases (including the current report), rituximab was rapidly effective in resolving chemotherapy-induced TTP/HUS that was refractory to plasma exchanges and glucocorticoids.ConclusionsRituximab may be indicated for early treatment of chemotherapy-induced TTP/HUS, particularly when plasma exchange is not rapidly effective.

Synovial chondromatosis of the temporomandibular joint: clinical, cytologic, histologic, radiologic, therapeutic aspects, and differential diagnosis of an uncommon lesion.

Synovial chondromatosis (SC) of the temporomandibular joint (TMJ) is a rare disorder with an indolent clinical course that leads to nonspecific symptoms, dysfunction, and anatomic distortion of the TMJ. We describe a case of SC in an 82-year-old male that presented as an incidental 2 cm cystic tumor of the left TMJ, during diagnostic work-up for unrelated symptoms. A fine needle aspiration of the lesion yielded fragments of abnormal mature cartilage and myxoid fluid. The diagnosis of SC was suggested after correlating the clinical and pathologic findings. Open TMJ surgery was performed for definitive diagnosis and therapy. This manuscript describes the clinical, radiologic, cytologic, and pathologic features of this entity, and relates the differential diagnosis to other cartilaginous lesions and neoplasms of the TMJ. Awareness of this disorder is important to provide adequate care and avoid overtreatment.

Occult primary medullary thyroid carcinoma presenting with pituitary and parotid metastases: Case report and review of the literature

Medullary thyroid carcinoma (MTC) accounts for <10% of all thyroid malignancies and is derived from the calcitoninproducing C cell [1, 2]. It is of particular interest because of its association with hereditary syndromes, aggressiveness, and refractoriness to adjuvant therapies, and its association with mutations in the RET (rearranged during transfection) proto-oncogene, which encodes a receptor tyrosine kinase that may be amenable to therapy with the recently available tyrosine kinase inhibitors (TKI) [3, 4]. Thyroid tumors metastasizing to the pituitary and parotid gland are rare, and medullary thyroid carcinoma metastatic to either site has only been reported in a handful of instances. Here, we report a rare case of an occult MTC, which presented with clinical symptoms associated with synchronous metastases diagnosis.

Expression and Phosphorylation of Eukaryotic Translation Initiation Factor 4E Binding Protein 1 in B-Cell Lymphomas and Reactive Lymphoid Tissues

CONTEXT Cap-mediated messenger RNA translation controlled by the eukaryotic initiation factor 4F (eIF-4F) complex plays a key role in human cancer. eIF-4F activity is controlled by a repressor binding protein (4E-BP1), which promotes translation when phosphorylated. OBJECTIVE To examine the level of expression and phosphorylation of 4E-BP1 in various subtypes of B-cell lymphoma and reactive lymphoid tissues. DESIGN Archival formalin-fixed, paraffin-embedded B-cell lymphoma samples and reactive lymphoid tissues were immunostained and examined for expression of 4E-BP1 and phosphorylated 4E-BP1. Expression of components of the eIF-4F complex and unphosphorylated and phosphorylated 4E-BP1 was confirmed using Western immunoblotting on lysates of frozen lymphoma samples and reactive tissues. RESULTS Immunohistochemical analysis demonstrated weak to undetectable 4E-BP1 staining within benign, reactive germinal centers (N = 10). In contrast, 4E-BP1 was consistently expressed (moderate to strong staining) in 98% of various subtypes of mature B-cell lymphoma (N = 50). 4E-BP1 expression was also demonstrable in all 4 lymph nodes with in situ or partial involvement by follicular lymphoma and in all 12 cases of BCL2-negative lymphoma. The level of phosphorylation of 4E-BP1 in lymphomas, evaluated by immunohistochemistry, was heterogeneous. CONCLUSIONS The immunohistochemical expression pattern of 4E-BP1 exhibits regional and cellular specificity in reactive lymphoid tissues and may offer a diagnostic tool for distinguishing reactive follicles from neoplastic B-cell proliferations.

The mystery of the vanishing Reinke crystals

Reinke crystals (RC) are pathognomonic of Leydig cells (LCs); they are thought to be rare in normal testes and to occur only in approximately one third of LC tumors. We noticed that crystals present in touch imprint and frozen sections of an LC tumor disappeared after tissue fixation. This phenomenon led us to hypothesize that their reported low frequency in normal and neoplastic LCs may be secondary to degradation/dissolution of the crystals after formalin fixation. Our review of the literature also led us to hypothesize that RC are better preserved after air-drying and alcohol fixation. We collected testicular samples from 21 autopsies including air-dried cytologic preparations and tissue samples that were fixed in alcohol or formalin. We found that RC are common in normal LC but dissolve rapidly in formalin and slowly and only partially in alcohol. The composition of RC is unknown; however, they have been reported to stain specifically for nestin, an intermediate filament expressed mainly in neural and muscle tissue. Because the crystals have only been described in androgen-producing cells, we hypothesized that the crystals may represent a crystallized form of androgenic hormones, hormone complexes, or enzymes involved in their synthesis. We performed immunostains for androgens and enzymes involved in androgenesis. We also performed nestin immunostain to confirm the previous study. The crystals stain specifically with antibodies anti-3β-hydroxysteroid dehydrogenase and are negative for the remaining androgenic enzymes, androgenic hormones, and nestin.

Refractory cytopenias with unilineage dysplasia: a retrospective analysis of refractory neutropenia and refractory thrombocytopenia.

The myelodysplastic syndromes (MDS) are stem cell disorders characterized by ineffective hematopoiesis and peripheral cytopenias [1]. Over 10 000 cases per year are diagnosed in the United States [2]. The incidence rises to 20–50/100 000 per year over the age of 60 [3]. The current World Health Organization (WHO) classification (2008) [4,5] includes a new diagnostic category of MDS: refractory cytopenias with unilineage dysplasia (RCUD), defined by 410% morphological dysplasia limited to a single myeloid lineage, 51% peripheral blood blasts, 55% bone marrow blasts, and unior bi-cytopenia (pancytopenia is not allowed). RCUD is further subdivided into refractory anemia (RA), refractory neutropenia (RN), and refractory thrombocytopenia (RT), according to the dominant peripheral cytopenia. While RA with ring sideroblasts (RARS) meets RCUD criteria, it is kept separate given its distinctive morphologic features. RA and RARS represent the majority of cases of MDS with unilineage dysplasia; RN and RT are considered rare, and extreme caution is recommended in making these latter diagnoses [4]. It is postulated that RN and RT exhibit low-risk features similar to RA/RARS. However, there is very limited clinical information reported about these new categories, and none from the United States. We report the incidence, presenting clinical and pathological features, clinical course, and outcomes of patients with RN and RT diagnosed and followed at a single center in the United States. We performed a retrospective review of 293 consecutive patients diagnosed with MDS (1992–2009) at the Minneapolis Veterans Affairs Medical Center (VAMC), with approval from the institutional human subjects committee. Cytopenias were defined as hemoglobin 510.0 g/dL, absolute neutrophil count 51.86 10/L, and platelet count 51006 10/L [6,7]. Diagnostic and follow-up peripheral smears and bone marrow specimens were reviewed by both hematopathologists (A.R. and H.M., blinded to clinical information) to re-confirm the diagnosis. Statistical analysis was performed using GraphPad Prism 5.0 (GraphPad Software Inc., San Diego, CA). Differences between groups were compared using a two-tailed t-test. The probabilities of overall survival (OS) were determined using the Kaplan– Meier method and compared by log-rank (Mantel– Cox) test. Amongst 293 consecutive patients diagnosed with MDS, five (1.7%) with RN and six (2.0%) with RT were identified, and compared with 27 (9.2%) patients diagnosed with RA/RARS during the same period (Supplementary Table S1). In studies of isolated cytopenias (other than anemia) in MDS published prior to the WHO 2008 classification, the incidence of isolated thrombocytopenia was reported to range from 1% [8] to 8.9% [9]. Fenaux et al. [10] reported the incidence of ‘RN/RT’ as 3.2% (eight RN, two RT, amongst 312 patients with MDS). However, since publication of the WHO 2008

Burned out testicular seminoma presenting as a primary gastric malignancy.

In contrast to primary gastric adenocarcinomas, germ cell tumors are potentially curable even when metastatic. It is therefore essential for clinicians and pathologists to be aware of the spectrum of unusual manifestations of germ cell malignancies. Here we report on a 55-year-old man who presented with clinical and endoscopic features indicative of a primary gastric carcinoma. Surprisingly, the ulcerative mucosal lesion was found to be due to a metastasis from an occult, “burned-out” testicular seminoma. This case describes the radiological and pathological features that helped differentiate this rare situation from the much more common gastric adenocarcinoma, and extends the diagnostic possibilities that must be considered in patients presenting with gastric ulcers.

Comparative immunomorphology of testicular Sertoli and sertoliform tumors

Sertoli cell (SC) and sertoliform tumors of the testis are very uncommon; for this reason their differential diagnosis and classification can be challenging. We applied an extensive immunophenotypic panel that included androgenic hormones, enzymes and receptors, neuroendocrine, lineage and genitourinary markers to a series of these lesions to determine if and which immunostains can aid in their diagnostic workup. Study cases included: 2 androgen insensitivity syndrome-associated SC adenomas, 3 SC tumors (SCT) not otherwise specified (SCT-NOS), 3 sclerosing SCT, 2 large cell calcifying SCT, 1 SCT with heterologous sarcomatous elements, 1 malignant SCT, and 1 sertoliform rete testis adenoma (sertoliform RTA). We found that SCT-NOS and variants with sclerosis showed a phenotype akin to atrophic seminiferous tubules characterized by gain of expression of pankeratin, calretinin, CD56, which are negative in normal SC. Distinctive phenotypes were identified in: sclerosing SCT: androgen receptors (AR) + (strong)/PAX2/PAX8+ (subset)/S100+/inhibin-; large cell calcifying SCT: calretinin+ (strong)/S100+/AR-; sertoliform RTA: PAX2/PAX8+/pankeratin+/inhibin-. Androgenic hormones and enzymes did not show diagnostic utility. A panel of calretinin, inhibin, pankeratin, S100, PAX2/PAX8, and AR consistently allowed distinction between variants of Sertoli and sertoliform tumors.