Amaka C. Offiah

A Mutation in the Thyroid Hormone Receptor Alpha Gene

Thyroid hormones exert their effects through alpha (TRα1) and beta (TRβ1 and TRβ2) receptors. Here we describe a child with classic features of hypothyroidism (growth retardation, developmental retardation, skeletal dysplasia, and severe constipation) but only borderline-abnormal thyroid hormone levels. Using whole-exome sequencing, we identified a de novo heterozygous nonsense mutation in a gene encoding thyroid hormone receptor alpha (THRA) and generating a mutant protein that inhibits wild-type receptor action in a dominant negative manner. Our observations are consistent with defective human TRα-mediated thyroid hormone resistance and substantiate the concept of hormone action through distinct receptor subtypes in different target tissues.

Muscle Magnetic Resonance Imaging Involvement in Muscular Dystrophies with Rigidity of the Spine

The aim of the study was to evaluate whether the visual analysis of muscle magnetic resonance imaging scans can identify specific patterns of muscle involvement.

Abnormal vertebral segmentation and the notch signaling pathway in man.

Abnormal vertebral segmentation (AVS) in man is a relatively common congenital malformation but cannot be subjected to the scientific analysis that is applied in animal models. Nevertheless, some spectacular advances in the cell biology and molecular genetics of somitogenesis in animal models have proved to be directly relevant to human disease. Some advances in our understanding have come through DNA linkage analysis in families demonstrating a clustering of AVS cases, as well as adopting a candidate gene approach. Only rarely do AVS phenotypes follow clear Mendelian inheritance, but three genes—DLL3, MESP2, and LNFG—have now been identified for spondylocostal dysostosis (SCD). SCD is characterized by extensive hemivertebrae, trunkal shortening, and abnormally aligned ribs with points of fusion. In familial cases clearly following a Mendelian pattern, autosomal recessive inheritance is more common than autosomal dominant and the genes identified are functional within the Notch signaling pathway. Other genes within the pathway cause diverse phenotypes such as Alagille syndrome (AGS) and CADASIL, conditions that may have their origin in defective vasculogenesis. Here, we deal mainly with SCD and AGS, and present a new classification system for AVS phenotypes, for which, hitherto, the terminology has been inconsistent and confusing. Developmental Dynamics 236:1456–1474, 2007.

The phenotype of survivors of campomelic dysplasia

Five patients with campomelic dysplasia who have survived (age range 7 to 20 years) are described, all of whom have molecular or cytogenetic evidence of campomelic dysplasia. The phenotype and radiological features of these cases are consistent. Complications in this group include recurrent apnoea and upper respiratory infections, progressive kyphoscoliosis, mild to moderate learning difficulties, short stature, and dislocation of the hips. All five had very similar facial features. The radiological features include hypoplastic scapulae, defective ischiopubic ossification, absent or hypoplastic patellae, and spinal dysraphism. Campomelic dysplasia (CMD) is a rare skeletal dysplasia resulting from mutations in SOX9. It is usually lethal in the first year of life. Three-quarters of the cases with a male karyotype have complete or partial sex reversal.1 The skeletal changes in the neonatal period are well recognised and include hypoplastic scapulae, bowing of the long bones, vertical narrow iliac bones, and absence of ossification of the thoracic pedicles. The case histories of five children who share a number of clinical and radiological features are presented. ### Case 1 A mother was diagnosed at the age of 18 years after giving birth to a daughter with the classical features of campomelic dysplasia.2 The daughter had shortening of all four limbs, tibial bowing, with skin dimpling over the apex of each tibia. There was bilateral talipes equinovarus and relative macrocephaly (head circumference on the 50th centile, length <3rd centile). She had micrognathia and a depressed nasal bridge. The karyotype was normal female. She had the classical radiological features of campomelic dysplasia with hypoplastic scapulae and absent pedicles in the mid-thoracic region, 11 pairs of ribs, shortening of the long bones with bowing, narrow iliac bones with dislocation of the hips, short first metacarpals, and short phalanges in the hands and feet.2 She died of respiratory problems in …

An Adult Female With Resistance to Thyroid Hormone Mediated by Defective Thyroid Hormone Receptor α

CONTEXT The first human cases (female, age 6 y; father and daughter, ages 47 and 11 y, respectively) with growth retardation/short stature, skeletal dysplasia, constipation, and defective thyroid receptor α (TRα) have been recently described. OBJECTIVE A 45-year-old, short, overweight female with cognitive impairment, epilepsy, and constipation was investigated. DESIGN AND INTERVENTION Clinical, biochemical, and radiological assessment and THRA sequencing were undertaken. The patients thyroid status and her biochemical and physiological parameters were evaluated at baseline and after T4 therapy. RESULTS The patient exhibits disproportionate short stature, macrocephaly, low free T4/free T3 ratio and rT3 levels, together with subnormal heart and basal metabolic rate. She is heterozygous for a novel frameshift/premature stop (Ala382ProfsX7) THRA mutation, generating a mutant TRα with constitutive corepressor binding and negligible coactivator recruitment, which inhibits its wild-type counterpart in a dominant-negative manner-both in vitro and in mutation-containing patient blood mononuclear cells studied ex vivo. Her alertness and constipation responded to T4 therapy, which readily suppressed TSH levels, raised basal metabolic rate, and normalized elevated muscle creatine kinase, but cardiac parameters (heart rate, contractility) remained relatively refractory. The patient and a previous childhood case showed reduced red cell mass with macrocytosis unresponsive to T4 therapy. CONCLUSIONS Clinical (short stature, macrocephaly, constipation) and biochemical (low free T4/free T3 ratio, subnormal rT3) findings that are congruent with previous cases and newly recognized features (epilepsy) in this adult female with defective TRα define a shared phenotype in TRα-mediated resistance to thyroid hormone, with differential tissue responses to T4 treatment.

Skeletal imaging of child abuse (non-accidental injury)

In recent years there has been a worldwide increased awareness that children are physically abused by their carers. Radiologists play a vital role in the detection of inflicted injuries. This article reviews the skeletal imaging findings seen in child abuse.

Pseudoachondroplasia and multiple epiphyseal dysplasia: A 7‐year comprehensive analysis of the known disease genes identify novel and recurrent mutations and provides an accurate assessment of their relative contribution

Pseudoachondroplasia (PSACH) and multiple epiphyseal dysplasia (MED) are relatively common skeletal dysplasias resulting in short‐limbed dwarfism, joint pain, and stiffness. PSACH and the largest proportion of autosomal dominant MED (AD‐MED) results from mutations in cartilage oligomeric matrix protein (COMP); however, AD‐MED is genetically heterogenous and can also result from mutations in matrilin‐3 (MATN3) and type IX collagen (COL9A1, COL9A2, and COL9A3). In contrast, autosomal recessive MED (rMED) appears to result exclusively from mutations in sulphate transporter solute carrier family 26 (SLC26A2). The diagnosis of PSACH and MED can be difficult for the nonexpert due to various complications and similarities with other related diseases and often mutation analysis is requested to either confirm or exclude the diagnosis. Since 2003, the European Skeletal Dysplasia Network (ESDN) has used an on‐line review system to efficiently diagnose cases referred to the network prior to mutation analysis. In this study, we present the molecular findings in 130 patients referred to ESDN, which includes the identification of novel and recurrent mutations in over 100 patients. Furthermore, this study provides the first indication of the relative contribution of each gene and confirms that they account for the majority of PSACH and MED. Hum Mutat 33:144–157, 2012.

Resistance to thyroid hormone caused by a mutation in thyroid hormone receptor (TR)α1 and TRα2: clinical, biochemical, and genetic analyses of three related patients

BACKGROUND The thyroid hormone receptor α gene (THRA) transcript is alternatively spliced to generate either thyroid hormone receptor (TR)α1 or a non-hormone-binding variant protein, TRα2, the function of which is unknown. Here, we describe the first patients identified with a mutation in THRA that affects both TRα1 and TRα2, and compare them with patients who have resistance to thyroid hormone owing to a mutation affecting only TRα1, to delineate the relative roles of TRα1 and TRα2. METHODS We did clinical, biochemical, and genetic analyses of an index case and her two sons. We assessed physical and radiological features, thyroid function, physiological and biochemical markers of thyroid hormone action, and THRA sequence. FINDINGS The patients presented in childhood with growth failure, developmental delay, and constipation, which improved after treatment with thyroxine, despite normal concentrations of circulating thyroid hormones. They had similar clinical (macrocephaly, broad faces, skin tags, motor dyspraxia, slow speech), biochemical (subnormal ratio of free thyroxine:free tri-iodothyronine [T3], low concentration of total reverse T3, high concentration of creatine kinase, mild anaemia), and radiological (thickened calvarium) features to patients with TRα1-mediated resistance to thyroid hormone, although our patients had a heterozygous mis-sense mutation (Ala263Val) in both TRα1 and TRα2 proteins. The Ala263Val mutant TRα1 inhibited the transcriptional function of normal receptor in a dominant-negative fashion. By contrast, function of Ala263Val mutant TRα2 matched its normal counterpart. In vitro, high concentrations of T3 restored transcriptional activity of Ala263Val mutant TRα1, and reversed the dominant-negative inhibition of its normal counterpart. High concentrations of T3 restored expression of thyroid hormone-responsive target genes in patient-derived blood cells. INTERPRETATION TRα1 seems to be the principal functional product of the THRA gene. Thyroxine treatment alleviates hormone resistance in patients with mutations affecting this gene, possibly ameliorating the phenotype. These findings will help the diagnosis and treatment of other patients with resistance to thyroid hormone resulting from mutations in THRA. FUNDING Wellcome Trust, NIHR Cambridge Biomedical Research Centre, Marie Curie Actions, Foundation for Development of Internal Medicine in Europe.

Post mortem magnetic resonance imaging in the fetus, infant and child: a comparative study with conventional autopsy (MaRIAS Protocol).

BackgroundMinimally invasive autopsy by post mortem magnetic resonance (MR) imaging has been suggested as an alternative for conventional autopsy in view of the declining consented autopsy rates. However, large prospective studies rigorously evaluating the accuracy of such an approach are lacking. We intend to compare the accuracy of a minimally invasive autopsy approach using post mortem MR imaging with that of conventional autopsy in fetuses, newborns and children for detection of the major pathological abnormalities and/or determination of the cause of death.Methods/DesignWe recruited 400 consecutive fetuses, newborns and children referred for conventional autopsy to one of the two participating hospitals over a three-year period. We acquired whole body post mortem MR imaging using a 1.5 T MR scanner (Avanto, Siemens Medical Solutions, Enlargen, Germany) prior to autopsy. The total scan time varied between 90 to 120 minutes. Each MR image was reported by a team of four specialist radiologists (paediatric neuroradiology, paediatric cardiology, paediatric chest & abdominal imaging and musculoskeletal imaging), blinded to the autopsy data. Conventional autopsy was performed according to the guidelines set down by the Royal College of Pathologists (UK) by experienced paediatric or perinatal pathologists, blinded to the MR data. The MR and autopsy data were recorded using predefined categorical variables by an independent person.DiscussionUsing conventional post mortem as the gold standard comparator, the MR images will be assessed for accuracy of the anatomical morphology, associated lesions, clinical usefulness of information and determination of the cause of death. The sensitivities, specificities and predictive values of post mortem MR alone and MR imaging along with other minimally invasive post mortem investigations will be presented for the final diagnosis, broad diagnostic categories and for specific diagnosis of each system.Clinical Trial RegistrationNCT01417962NIHR Portfolio Number: 6794

Assessment of active inflammation in juvenile dermatomyositis: a novel magnetic resonance imaging-based scoring system

OBJECTIVE To assess the reproducibility of a novel scoring system that we have developed for the objective assessment of acute inflammatory change in JDM. This system defines markers of inflammatory change in four muscle groups and the surrounding soft tissues. METHODS Forty-eight children (33 girls) underwent retrospective assessment of their MRI studies by two musculoskeletal paediatric radiologists for the presence of disease activity. Each observer performed the readings on two separate occasions. The degree of concordance between the two observers and between the two readings was assessed using kappa analysis. The reproducibility of the total score was determined using Bland-Altman analysis. RESULTS There was fair to moderate agreement between the two observers for all the examined disease activity markers in all muscle groups. There was good intra-observer agreement between the two readings. There was no difference according to the side evaluated. The mean total score (out of 20) for Observer 1 was 7.9 and for Observer 2 was 7.5 (mean difference -0.4, 95% limits of agreement -6.8 to 6.0), while the mean total scores for Observer 1 were 9.0 for the first reading and 7.9 for the second reading (mean difference 1.0, 95% limits of agreement -2.6 to 4.6). CONCLUSION Markers of inflammatory change in JDM can be observed on MRI in a reliable fashion and have been used to make a reliable and objective scoring system. The accuracy of the proposed scoring system is acceptable for the single reader, although there is more variability between two different individuals.