Genotype-phenotype analysis, and assessment of the importance of the zinc-binding site in PHEX in Japanese patients with X-linked hypophosphatemic rickets using 3D structure modeling.

X-linked hypophosphatemic rickets (XLH) is an inheritable type of rickets caused by inactivating variants in the phosphate regulating endopeptidase homolog X-linked (PHEX) gene, which results in the overproduction of fibroblast growth factor 23 (FGF23). The mechanism by which PHEX impairment leads to FGF23 overproduction is unknown. Because little is known regarding the genotype-phenotype correlation in Japanese XLH, we summarized the available clinical and genetic data and analyzed the genotype-phenotype relationships using 3-dimensional (3D) structure modeling to clarify the XLH pathophysiology. We retrospectively reviewed the clinical features and performed genetic analysis of 39 Japanese patients with XLH from 28 unrelated pedigrees carrying any known or novel PHEX variant. To predict changes in the 3D structure of mutant PHEX, we constructed a putative 3D model of each mutant and evaluated the effect of structural alteration by genotype-phenotype correlation analysis. Genetic analysis revealed 23 PHEX variants, including eight novel variants. They were associated with high i-FGF23 levels, hypophosphatemia, phosphaturia, high alkaline phosphatase levels, and short stature. No gene dosage effect or genotype-phenotype correlation was observed when truncating and non-truncating variants were compared. However, the conservation of the zinc-binding site and cavity in PHEX had an impact on the elevation of i-FGF23 levels. Via genotype-phenotype relationship analysis using 3D modeling, we showed that the zinc-binding site and cavity in PHEX can play a critical role in its function. These findings provide new genetic clues for investigating the function of PHEX and the pathogenesis of XLH.

One Novel and Two Recurrent THRB Mutations Associated with Resistance to Thyroid Hormone: Structure-based Computational Mutation Prediction.

Inactivating mutations of THRB, which encodes the thyroid hormone receptor ß (TRß), cause resistance to thyroid hormone (RTH; OMIM 190160). To date, more than 100 THRB mutations have been reported among RTH patients. Most mutations substitute a single amino-acid residue in the ligand-binding domain. In this report, we describe clinical and molecular findings of three families with RTH. Three families harbored one novel (p.I431M) and two recurrent (p.R320H and p.R383C) THRB mutations. To examine the pathogenicity of identified mutations, we introduced a novel computational mutation prediction method based on three-dimensional structure data of TRß-T3 complex. First, to define the accuracy of our prediction system, we evaluated ten previously reported 'positive control' mutations, as well as 30 seemingly benign sequence variations observed among vertebral species as 'negative controls'. We found that our system had a sensitivity of 80% and a specificity of 93%. We then analyzed three mutations detected in the present study and found that all three mutations are predicted to be deleterious. Our data suggest that our structure-based prediction system would be a prompt, inexpensive and feasible method for evaluating the pathogenicity of missense THRB mutations.

Proinflammatory cytokines in cerebrospinal fluid from patients with nontyphoidal Salmonella encephalopathy.

Nontyphoidal Salmonella (NTS) encephalopathy is characterized by rapidly progressive brain dysfunction that develops after NTS enteritis. The mechanism of central nervous system involvement remains unclear. We examined cerebrospinal fluids from 7 patients for cytokines and found elevated interleukin-6, interleukin-8, and monocyte chemotactic protein-1 concentrations in all the patients, suggesting that the proinflammatory cytokines are involved in the pathogenesis of NTS encephalopathy.

Bilateral asynchronous adrenocortical adenoma in a girl with beckwith-wiedemann syndrome.

We report a case of asynchronous occurrence of bilateral adrenocortical adenoma in a 13-yr-old girl with Beckwith-Wiedemann syndrome. A right virilizing adrenal adenoma was surgically removed at age 6, following clinical manifestation of virilization such as acne, voice change, clitoris hypertrophy and overgrowth. Histopathological examination of the resected specimen revealed an adrenocortical adenoma predominantly composed of eosinophilic tumor cells expressing all the steroidogenic enzymes. High serum levels of DHEA-S (6,380 ng/ml) and testosterone (547 ng/dl) were noted prior to the operation. Postoperative course was unremarkable. Menstruation started at age 11, with a regular interval. At the age of 13 yr old, a high serum level of DHEA-S (8,250 ng/ml) was detected. In contrast to the episode of virilization at age 6, however, the serum testosterone level was not so high (122 ng/dl), and no clinical symptoms of virilization were apparent. Abdominal ultrasonography demonstrated the presence of a left adrenocortical adenoma. Pathological examination of the resected specimen revealed a circumscribed and well encapsulated tumor with essentially the same histological features as the tumor previously removed, except that the tumor cells showed a more prominent morphological similarity to the fetal adrenal cortex and did not express 3ß HSD. The absence of virilization at the second episode was due to the relatively low serum level of testosterone compared with that of DHEA-S.

Retrospective analysis of infants designated as positive on mass-screening for congenital hypothyroidism at kagoshima university.

Mass-screening for congenital hypothyroidism has identified cases of mild hypothyroidism, transient hypothyroidism, and transient hyperthyrotropinemia as well as typical hypothyroidism. In this paper, we examine the clinical data of the cases found positive in the screening test at our hospital. From 1989 to 1999 there were 72 patients with positive screening tests who started levothyroxine sodium (l-T4; Thyradin-S) as supplement therapy. At the age of 3 to 4 yr the patients were re-evaluated to determine whether treatment should be continued. Thyroid scintigraphies were done at the same time. We divided these cases into 4 groups. Those in group 1A started l-T4 in early infancy without a TRH test because of obvious clinical evidence of hypothyroidism, and treatment was continued after re-evaluation (n=37). Those in group 1B also started treatment in early infancy without a TRH test, but treatment was discontinued after re-evaluation (n=20). Patients in group 2A started l-T4 after evaluation by a TRH test and treatment was continued after re-evaluation (n=14), while those in group 2B started treatment after a TRH test, but after re-evaluation, treatment was discontinued (n=1). In group 2A, only a low dose of l-T4 was needed, and a slightly elevated TSH and slightly decreased free T4 (FT4) were observed after the drug washout period. However, these patients had an exaggerated response to the TRH test at re-evaluation. These findings indicate that this group, forming not a small part of whole screening-positive subjects, had mild hypothyroidism. Such patients require careful follow-up and repeated evaluation to determine whether treatment should be continued.

A case with hyperthyroidism who had been treated with thyroid hormone because of congenital hypothyroidism.

We encountered a case with hyperthyroidism at the age of 14 who had been diagnosed with congenital hypothyroidism (CH) and had received thyroid hormone replacement therapy. At the age of 16 d, the patient was referred to our hospital because of positive results at neonatal screening for CH. Serum level of TSH was 91.0 µU/ml and serum level of T4 was 6.9 µg/dl. The patient was diagnosed as having hypothyroidism, and hormone replacement therapy was started. Thereafter the dosage of thyroid hormone was adjusted and increased gradually as he grew to a maximum dose of 110 µg/day at the age of 11. Until the age of 13, the patient's serum levels of TSH were within the normal range; then, at the age of 13 yr and 4 mo, his serum level of TSH dropped to a level below the detectable range. The dosage of administered thyroid hormone was tapered off and eventually eliminated at the age of 14. A thyroid scan and a radioactive iodine uptake test demonstrated a diffuse goiter with homogeneous uptake of radioactive iodine; the uptake rate was 60% at 24 h, and the serum level of TSH receptor antibody (TRAb) was 62.5% at that time. Administration of an antithyroid drug was started after confirmation that our patient had developed hyperthyroidism. There have been no case reports similar to our case.