Paul S. Thorner

Regulation of glomerular basement membrane collagen expression by LMX1B contributes to renal disease in nail patella syndrome

Basement membrane (BM) morphogenesis is critical for normal kidney function. Heterotrimeric type IV collagen, composed of different combinations of six α-chains (1–6), is a major matrix component of all BMs (ref. 2). Unlike in other BMs, glomerular BM (GBM) contains primarily the α3(IV) and α4(IV) chains, together with the α5(IV) chain. A poorly understood, coordinated temporal and spatial switch in gene expression from ubiquitously expressed α1(IV) and α2(IV) collagen to the α3(IV), α4(IV) and α5(IV) chains occurs during normal embryogenesis of GBM (ref. 4). Structural abnormalities of type IV collagen have been associated with diverse biological processes including defects in molecular filtration in Alport syndrome, cell differentiation in hereditary leiomyomatosis, and autoimmunity in Goodpasture syndrome; however, the transcriptional and developmental regulation of type IV collagen expression is unknown. Nail patella syndrome (NPS) is caused by mutations in LMX1B, encoding a LIM homeodomain transcription factor. Some patients have nephrosis-associated renal disease characterized by typical ultrastructural abnormalities of GBM (refs. 8,9). In Lmx1b−/− mice, expression of both α(3)IV and α(4)IV collagen is strongly diminished in GBM, whereas that of α1, α2 and α5(IV) collagen is unchanged. Moreover, LMX1B binds specifically to a putative enhancer sequence in intron 1 of both mouse and human COL4A4 and upregulates reporter constructs containing this enhancer-like sequence. These data indicate that LMX1B directly regulates the coordinated expression of α3(IV) and α4(IV) collagen required for normal GBM morphogenesis and that its dysregulation in GBM contributes to the renal pathology and nephrosis in NPS.

In vivo identification of Langerhans and related dendritic cells infected with HIV-1 subtype E in vaginal mucosa of asymptomatic patients

In Thailand, the predominant HIV subtype is E, rather than Subtype B as in North America and Europe, and the predominant mode of transmission is heterosexual contact. Subtype E has the ability to replicate in vitro in Langerhans cells. We hypothesized that this cell type might constitute a reservoir for the HIV virus in vaginal mucosa of asymptomatic carriers. To examine this hypothesis, we compared vaginal tissue histology in HIV-1–seropositive cases with seronegative cases and determined the immunophenotype of HIV-1–infected cells, their numbers, and their distribution in vaginal mucosa. Vaginal biopsies were performed at four different sites from six asymptomatic HIV-1 Subtype E–infected persons and from six seronegative cases at necropsy and examined histologically. Immunophenotyping was performed using immunoperoxidase for Gag p24 HIV, CD3, CD20, CD68, CD1a, S-100 and p55 antigens and by double labeling, combining immunoperoxidase with alkaline phosphatase using pairs of the above antigens. Twenty of twenty-four vaginal biopsies (83.3%) from HIV-seropositive cases showed definite inflammation compared to five of twenty-four vaginal necropsies (20.8%) from HIV-seronegative cases. One third of HIV-seropositive biopsies (8/24) demonstrated p24-positive cells in the epithelium, whereas three-fourths (18/24) of the biopsies revealed p24-positive cells in the lamina propria. All seropositive patients showed positive cells in at least one biopsy, but not all biopsies contained positive cells. Infected cells were more frequently observed at sites of greater inflammation. The dendritic cell count in HIV-seropositive vaginal epithelium was significantly higher than that observed in the seronegative cases (P =.004). The majority of p24-positive cells in the vaginal epithelium were Langerhans cells (CD1a+/S-100+), whereas in the lamina propria, about half of p24-positive cells were Langerhans-related dendritic cells (p55+ and S-100+) and half were T lymphocytes. In conclusion, the increased propensity for heterosexual transmission of Subtype E may be related to vaginal inflammation, leading to the accumulation of Langerhans cells and related dendritic cells which, once infected with HIV, can act as a reservoir for further virus transmission.

The Inner Ear of Dogs with X-Linked Nephritis Provides Clues to the Pathogenesis of Hearing Loss in X-Linked Alport Syndrome

Alport syndrome is an inherited disorder of type IV collagen with progressive nephropathy, ocular abnormalities, and high-tone sensorineural deafness. In X-linked Alport syndrome, mutations in the COL4A5 gene encoding the alpha5 chain of type IV collagen lead to loss of the alpha3/alpha4/alpha5 network and increased susceptibility of the glomerular basement membrane to long-term damage. The molecular defects that underlie the otopathology in this disease remain poorly understood. We used a canine model of X-linked Alport syndrome to determine the expression of type IV collagen alpha-chains in the inner ear. By 1 month in normal adult dogs, the alpha3, alpha4, and alpha5 chains were co-expressed in a thin continuous line extending along the basilar membrane and the internal and external sulci, with the strongest expression along the lateral aspect of the spiral ligament in the basal turn of the cochlea. Affected dogs showed complete absence of the alpha3/alpha4/alpha5 network. The lateral aspect of the spiral ligament is populated by tension fibroblasts that express alpha-smooth muscle actin and nonmuscle myosin and are postulated to generate radial tension on the basilar membrane via the extracellular matrix for reception of high frequency sound. We propose that in Alport syndrome, the loss of the alpha3/alpha4/alpha5 network eventually weakens the interaction of these cells with their extracellular matrix, resulting in reduced tension on the basilar membrane and the inability to respond to high frequency sounds.

MRI of fibromatosis: With pathologic correlation

Fibromatosis refers to group of benign but sometimes locally aggressive proliferative lesions of myofibroblasts. These are characterized by infiltrative growth, and hence may mimic a malignant lesion. These lesions reveal a low signal intensity on T1-weighted pulse sequences, but may show low or high signal intensity on the T2-weighted sequences. Histologic correlation reveals that the lesion showing low signal intensity on T2-weighted sequences has a larger collagenous component, and reduced cellularity comoared with the lesion showing high signal intensity on T2-weighted sequences.

Lymphadenopathy due to Penicillium marneffei infection: Diagnosis by fine needle aspiration cytology

Penicillium marneffei is an opportunistic fungal infection that usually causes disseminated disease, mainly in immunocompromised individuals, especially those with HIV infection. Untreated cases are usually fatal. Diagnosis is traditionally made by biopsy and/or culture; successful diagnosis by fine needle aspiration (FNA) has only been reported once. We present eight cases of HIV-infected patients with lymphadenopathy caused by P. marneffei infection, in which the diagnosis was made by FNA. In all cases, intracellular and extracellular yeast forms were visualized, and the characteristic cross-septation of P. marneffei was highlighted by GMS staining. All diagnoses were confirmed by culture. Anti-fungal treatment for P. marneffei was initiated, resulting in marked clinical improvement. We conclude that a diagnosis of lymphadenopathy caused by P. marneffei can reliably be made by FNA. The diagnosis is more rapid than biopsy or culture, allowing rapid institution of therapy, particularly important in immunocompromised patients. In all our cases, not only were lymphoma and other causes of lymphadenopathy ruled out, but also the necessity for an open surgical biopsy was obviated. This can be especially beneficial to patients (e.g., three in our study) in which lymphadenopathy is confined to deep intra-abdominal nodes.

Cell reservoirs in lymph nodes infected with HIV-1 subtype E differ from subtype B: identification by combined in situ polymerase chain reaction and immunohistochemistry

In Thailand, the predominant HIV subtype is E, rather than subtype B as in North America and Europe. Subtype E has the ability to replicate in vitro in Langerhans cells. We hypothesized that this cell type might constitute a reservoir for the HIV virus in infected lymph nodes. We examined lymph nodes from 25 HIV-1 subtype E-infected patients to determine the immunophenotype of HIV-1-infected cells, their numbers and their distribution. The presence of HIV was detected either by in situ reverse transcriptase-polymerase chain reaction or immunoperoxidase. Cell identity was determined by double labelling using alkaline phosphatase-based immunohistochemistry. The majority of HIV-infected cells in the lymph nodes were Langerhans cells (CD1a+S100+) and Langerhans-related dendritic cells (p55+S100+). These cells were located in the paracortical areas of lymph nodes, with a few cells scattered at the edges of germinal centers, but were absent from germinal centers themselves, in contrast to the reported distribution of subtype B virus. In addition, multinucleated giant cells were significantly more common in HIV-infected nodes (64%) compared to controls (4%) (P=0.00002). In conclusion, Langerhans histiocytes and related cells are reservoirs for HIV subtype E in lymph nodes. Disrupting the pathway of infection of Langerhans cells and related cells may be a viable strategy to interfere with transmission of HIV subtype E.

Sonographic appearance of Sertoli cell tumour: With pathologic correlation

Sertoli cell tumor is a rare tumor of the testis, with a good prognosis following orchiectomy in the pediatric patient. Sonography of such a tumor in a 5-year-old boy revealed diffuse inhomogeneous increase in echogenicity in an enlarged left testicle. The increased echogenicity of the testicle reflected the dense collagenous matrix of the lesion.

Pathological Features of Multiple Endocrine Neoplasia Type IIb in Childhood

The features of two patients with multiple endocrine neoplasia type IIb are described. Patient 1, a 9-year-old boy with marfanoid features, presented with chronic constipation and failure to thrive since infancy. Patient 2, a 12-year-old boy with marfanoid features, presented with a five-year history of persistent cervical lymphadenopathy. In patient 1, the myenteric and submucosal nerve plexuses at all levels of the small and large intestines were comprised of diffusely disorganized, hyperplastic, mature ganglion cells and nonmyelinated nerve fibers. Nerve plexus dissection with morphometric analysis showed marked thickening of the myenteric plexus with a quantitative increase in neural tissue. Patient 2 had a submucosal neuroma of the tongue. Both patients had occult medullary thyroid carcinoma, and patient 2 had cervical lymph node metastases. Both neoplasms showed positive staining for cytokeratin, carcinoembryonic antigen, calcitonin, bombesin, chromogranin, serotonin, and Leu 7. Electron microscopy showed membrane-bound, intermediate-sized, dense-core neurosecretory granules in tumor cells. In patient 2, calcitonin-positive amyloid was present with localization of calcitonin by immunoelectron microscopy to cytoplasmic secretory granules and to extracellular amyloid fibrils. These cases illustrate the potential for missed or delayed diagnosis in multiple endocrine neoplasia syndromes.

Angiostrongylus cantonensis infection mimicking a spinal cord tumor

Angiostrongylus cantonensis is the most common cause of eosinophilic meningitis and meningoencephalitis. Almost all cases are self‐limiting and are diagnosed by cerebrospinal fluid eosinophilia and enzyme‐linked immunosorbent assay; pathology reports are restricted to postmortem samples from lethal cases. We report on what we believe is the first case of A. cantonensis infection diagnosed by biopsy in a living patient. The spinal cord was biopsied because of the unusual clinical presentation of a myelopathy without meningeal symptoms, together with a mass lesion that was clinically and radiologically diagnosed as a spinal cord tumor.

Neonatal, severe primary hyperparathyroidism: a 7-year clinical and radiological follow-up of one patient

Abstract. Neonatal primary hyperparathyroidism is a rare entity characterized by marked hypercalcemia, diffuse parathyroid hyperplasia, and skeletal demineralization. It is often lethal unless total parathyroidectomy is performed. Long-term outcome of treated patients is poorly documented. We report the clinical and radiographic outcome of this disease in a 7-year-old boy who underwent a total parathyroidectomy and autotransplantation of a fragment of one parathyroid gland to his thigh in the neonatal period. This paper demonstrates the importance of prompt diagnosis and management in neonatal hyperparathyroidism and the role of various imaging modalities in its diagnosis and follow-up.