Frederik G. Dikkers

Identification of a 52 kb deletion downstream of the SOST gene in patients with van Buchem disease

Van Buchem disease is an autosomal recessive skeletal dysplasia characterised by generalised bone overgrowth, predominantly in the skull and mandible. Clinical complications including facial nerve palsy, optic atrophy, and impaired hearing occur in most patients. These features are very similar to those of sclerosteosis and the two conditions are only differentiated by the hand malformations and the tall stature appearing in sclerosteosis. Using an extended Dutch inbred van Buchem family and two inbred sclerosteosis families, we mapped both disease genes to the same region on chromosome 17q12-q21, supporting the hypothesis that van Buchem disease and sclerosteosis are caused by mutations in the same gene. In a previous study, we positionally cloned a novel gene, called SOST, from the linkage interval and identified three different, homozygous mutations in the SOST gene in sclerosteosis patients leading to loss of function of the underlying protein. The present study focuses on the identification of a 52 kb deletion in all patients from the van Buchem family. The deletion, which results from a homologous recombination between Alu sequences, starts approximately 35 kb downstream of the SOST gene. Since no evidence was found for the presence of a gene within the deleted region, we hypothesise that the presence of the deletion leads to a down regulation of the transcription of the SOST gene by a cis regulatory action or a position effect.

Benign Lesions of the Vocal Folds: Histopathology and Phonotrauma

Benign lesions of the vocal folds have various appearances. Histopathologic examination might provide the true diagnosis. Therefore, histologic slides of 74 patients (92 vocal folds) with clinically well-defined diagnoses were single-blind examined by a pathologist. Single histologic features did not differentiate between different clinical entities, but combinations make some diagnoses more likely than others. Ultrastructural examination of submucosal vessels in the three most common clinical entities (polyps, Reinke edema, and vocal fold nodules) showed an entity-unique pattern of abnormal increase of layers of basement membrane—like material. A potential pathogenetic model of benign lesions of the vocal folds is presented, employing a combination of histopathologic findings and their possible relations with various forms of trauma inducing and maintaining these lesions.

HUMAN PAPILLOMAVIRUS INFECTIONS IN LARYNGEAL CANCER

Although the association and clinical significance of human papillomavirus (HPV) infections with a subset of head and neck cancers, particularly for oropharyngeal carcinoma, has recently been well documented, the involvement of HPV in laryngeal cancer has been inadequately evaluated. Herein we review the currently known associations of HPV infections in diseases of the larynx and their potential for oncogenicity. Using several methods of detection, HPV DNA has been detected in benign (papillomatosis), indolent (verrucous carcinoma), and malignant (squamous cell carcinoma) lesions of the larynx. Consistent with the known oncogenic risk of HPV infections, common HPV types associated with laryngeal papillomatosis include low‐risk HPV types 6 and 11, with high‐risk HPV types 16 and 18 more commonly present in neoplastic lesions (verrucous carcinoma and squamous cell carcinoma). Although a broad range of prevalence has been noted in individual studies, approximately 25% of laryngeal squamous cell carcinomas harbor HPV infections on meta‐analysis, with common involvement of high‐risk HPV types 16 (highest frequency) and 18. Preliminary results suggest that these high‐risk HPV infections seem to be biologically relevant in laryngeal carcinogenesis, manifested as having viral DNA integration in the cancer cell genome and increased expression of the p16 protein. Despite this knowledge, the clinical significance of these infections and the implications on disease prevention and treatment are unclear and require further investigation.

Sclerostin in Mineralized Matrices and van Buchem Disease

Sclerostin is an inhibitor of bone formation expressed by osteocytes. We hypothesized that sclerostin is expressed by cells of the same origin and also embedded within mineralized matrices. In this study, we analyzed (a) sclerostin expression using immunohistochemistry, (b) whether the genomic defect in individuals with van Buchem disease (VBD) was associated with the absence of sclerostin expression, and (c) whether this was associated with hypercementosis. Sclerostin was expressed by cementocytes in mouse and human teeth and by mineralized hypertrophic chondrocytes in the human growth plate. In individuals with VBD, sclerostin expression was absent or strongly decreased in osteocytes and cementocytes. This was associated with increased bone formation, but no overt changes in cementum thickness. In conclusion, sclerostin is expressed by all 3 terminally differentiated cell types embedded within mineralized matrices: osteocytes, cementocytes, and hypertrophic chondrocytes.

Van Buchem disease: clinical, biochemical, and densitometric features of patients and disease carriers.

Van Buchem disease (VBD) is a rare bone sclerosing dysplasia caused by the lack of a regulatory element of the SOST gene, which encodes for sclerostin, an osteocyte‐derived negative regulator of bone formation. We studied the demographic, clinical, biochemical, and densitometric features of 15 patients with VBD (12 adults and 3 children) and 28 related carriers of the gene mutation. The most common clinical findings in patients were facial palsy (100%) and various degrees of hearing impairment (93%); raised intracranial pressure had been documented in 20%. The clinical course of the disease appeared to stabilize in adulthood, with the majority of patients reporting no progression of symptoms or development of complications with time. Carriers of the disease had none of the clinical features or complications of the disease. Sclerostin could be detected in the serum in all but 1 VBD patients (mean 8.0 pg/mL; 95% confidence interval [CI], 4.9–11.0 pg/mL), and were lower than those of carriers (mean 28.7 pg/mL; 95% CI, 24.5–32.9 pg/mL; p < 0.001) and healthy controls (mean 40.0 pg/mL; 95% CI, 34.5–41.0 pg/mL; p < 0.). Serum procollagen type 1 amino‐terminal propeptide (P1NP) levels were also significantly higher in adult patients (mean 96.0; 95% CI, 54.6–137.4 ng/mL versus mean 47.8; 95% CI, 39.4–56.2 ng/mL, p = 0.003 in carriers and mean 37.8; 95% CI, 34.5–41.0 ng/mL, p = 0.028 in healthy controls) and declined with age. Bone mineral density (BMD) was markedly increased in all patients (mean Z‐score 8.7 ± 2.1 and 9.5 ± 1.9 at the femoral neck and spine, respectively); BMD of carriers was significantly lower than that of patients but varied widely (mean Z‐scores 0.9 ± 1.0 and 1.3 ± 1.5 at the femoral neck and spine, respectively). Serum sclerostin levels were inversely correlated with serum P1NP levels (r = –0.39, p = 0.018) and BMD values (femoral neck r = –0.69, p < 0.001; lumbar spine r = –0.78, p < 0.001). Our results show that there is a gene‐dose effect of the VBD deletion on circulating sclerostin and provide further in vivo evidence of the role of sclerostin in bone formation in humans. The small amounts of sclerostin produced by patients with VBD may explain their milder phenotype compared to that of patients with sclerosteosis, in whom serum sclerostin is undetectable.

Higher laryngeal preservation rate after CO2 laser surgery compared with radiotherapy in T1a glottic laryngeal carcinoma

Clinical outcome of endoscopic CO2 laser surgery and radiotherapy in early‐stage glottic laryngeal carcinoma is difficult to compare because of differences in treatment selection and patient groups. Therefore, we compared local control, overall survival, and laryngeal preservation in a homogenous group of patients with T1a glottic carcinoma with normal/diminished mucosal wave treated with either CO2 laser surgery or radiotherapy.

Side-effects of cidofovir in the treatment of recurrent respiratory papillomatosis

Recurrent respiratory papillomatosis (RRP) is a chronic and difficult to treat disease of the larynx. In 1998, the first article was published that described the use of the antiviral substance cidofovir to treat this disease. Although the results are promising, there remains some concern about the potential carcinogenicity of cidofovir. There is a demand for a qualitative review of the side-effects of this medicine. In this review, the side-effects of cidofovir are investigated. Special attention was given to the potential carcinogenicity of cidofovir. For this review a search is performed in PubMed and EMBASE for relevant articles in which the use of intralesional cidofovir for patients with RRP is described. Eventually, 31 articles could be included for this review. In these articles a total of 188 patients with RRP were described who underwent therapy with intralesional cidofovir. Five of these patients have developed dysplasia of the larynx during the treatment with cidofovir. This is a percentage of 2.7. This percentage is concurrent with the incidence of spontaneous malignant degeneration of RRP (2–3%). Based on this review, it can be concluded that the use of intralesional cidofovir does not increase the risk of laryngeal dysplasia. Apart from the articles that describe the intralesional administration of cidofovir, some articles have been published in which the use of intravenous cidofovir is described as a therapy for RRP. Therefore, a summary is given on the side-effects of intralesional cidofovir as well as a summary on the reported side-effects of the intravenous administration of cidofovir. Based on the outcomes of this review, recommendations are given for a safe use of cidofovir for treatment of recurrent respiratory papillomatosis in the future.

Lamina Propria of the Mucosa of Benign Lesions of the Vocal Folds

Objective/Hypothesis: To demonstrate a correlation between the duration and specific pattern of trauma of benign lesions of the vocal folds and their histopathologic appearance. Benign lesions of the vocal folds have various macroscopic appearances. Investigations demonstrate characteristic histopathologic features for three clinically well‐defined lesions: 1) vocal fold polyps, 2) Reinke edema, and 3) vocal fold nodules. It is expected that additional histological stainings can contribute to additional insight into the pathophysiology of these lesions.

Laryngeal Amyloidosis: Localized versus Systemic Disease and Update on Diagnosis and Therapy

The clinical and pathological characteristics, possibility of systemic disease, and effect of local therapy were studied in laryngeal amyloidosis. Records of all patients with localized laryngeal amyloidosis in a single tertiary referral center were examined retrospectively at diagnosis and after local therapy. Of 188 new patients with amyloidosis between 1990 and 2003, 5 patients had localized laryngeal amyloidosis. A sixth patient with localized laryngeal amyloidosis turned out to have systemic AL (immunocyte-derived) amyloidosis 8 years later. Free light chains were found in this patient, as well as in 1 of the other 5 patients. Amyloid interfering with laryngeal or airway function was removed during microlaryngoscopy with a carbon dioxide laser or cold endoscopic excision. The best results were seen when glottic deposits were removed by cold endoscopic excision, and supraglottic deposits by a carbon dioxide laser. Four patients had recurrent disease. A systematic workup, including measurement of free light chains, helps to rule out systemic disease.

Ultrastructural changes of the basement membrane zone in benign lesions of the vocal folds.

The basement membrane zone (BMZ) of the epithelium of the vocal folds was investigated electron microscopically in 10 patients suffering from various benign lesions and in 3 controls. Various defects were observed: a thickening by deposition of electron dense material, a loss of normal architecture, and a near absence of normal hemidesmosomes and anchoring fibers. Beside these previously reported phenomena, many vesicles carrying electron dense material were found near the plasma membrane. The vesicles were observed at various stages of fusion with the plasma membrane, on the other side of which their content was discharged. In the cytoplasm an increase of mitochondria was seen. The amount of condensed chromatin decreased while the nucleoli increased in comparison with the controls. These observations are suggestive of a hyperactivity of the basal cells of the epithelium in response to vibratory stress.