Marianna Di Frenna

A frequent oligogenic involvement in congenital hypothyroidism

Congenital hypothyroidism (CH), the most frequent form of preventable mental retardation, is predicted to have a relevant genetic origin. However, CH is frequently reported to be sporadic and candidate gene variations were found inu2009<10% of the investigated patients. Here, we characterize the involvement of 11 candidate genes through a systematic Next Generation Sequencing (NGS) analysis. The NGS was performed in 177 unrelated CH patients (94 gland-in-situ; 83 dysgenesis) and in 3,538 control subjects. Non-synonymous or splicing rare variants (MAFu2009<u20090.01) were accepted, and their functional impact was predicted by a comprehensive bioinformatic approach and co-segregation studies. The frequency of variations in cases and controls was extended to 18 CH-unrelated genes. At least one rare variant was accepted in 103/177 patients. Monogenic recessive forms of the disease were found in five cases, but oligogenic involvement was detected in 39 patients. The 167 variations were found to affect all genes independently of the CH phenotype. These findings were replicated in an independent cohort of additional 145 CH cases. When compared to 3,538 controls, the CH population was significantly enriched with disrupting variants in the candidate genes (Pu2009=u20095.5u2009×u200910-7), but not with rare variations in CH-unrelated genes. Co-segregation studies of the hypothyroid phenotype with multiple gene variants in several pedigrees confirmed the potential oligogenic origin of CH. The systematic NGS approach reveals the frequent combination of rare variations in morphogenetic or functional candidate genes in CH patients independently of phenotype. The oligogenic origin represents a suitable explanation for the frequent sporadic CH occurrence.

Difficult treatment of consumptive hypothyroidism in a child with massive parotid hemangioma.

Abstract Consumptive hypothyroidism is a rare condition related to massive infantile hemangiomas producing an excess of the thyroid-hormone-inactivating enzyme type 3 iodothyronine deiodinase. We report the first case of consumptive hypothyroidism secondary to a large parotid hemangioma, highlighting the difficulties in selecting an adequate therapeutic strategy. The affected child was initially referred to our center for congenital hypothyroidism with a hypoplastic thyroid gland. l-Thyroxine (l-T4) replacement therapy was started at seven days of life. In the following weeks, the hemangioma rapidly increased in volume and the child developed severe hypothyroidism refractory to high doses of l-T4 therapy. The concentration of reverse triiodothyronine was elevated, suggesting that the underlying cause was an excessive conversion of thyroid hormones by high type 3 iodothyronine deiodinase levels in the tumor. Corticosteroid treatment showed only partial benefit. Introduction of propranolol instead led to normalization of thyroid hormones along with a dramatic involution of the hemangioma.

Novel NKX2-1 Frameshift Mutations in Patients with Atypical Phenotypes of the Brain-Lung-Thyroid Syndrome

Objectives: To verify the involvement of NKX2-1 gene in infants with brain-lung-thyroid (BLT) syndrome and hypothyroid phenotypes variable among congenital hypothyroidism (CH) or idiopathic mild hypothyroidism (IMH) of postnatal onset. Methods: The candidates were selected by a case-finding approach in 130 CH and 53 IMH infants. The NKX2-1 gene was analyzed by direct sequencing and multiplex ligation-dependent probe amplification. The variants were studied in vitro, by expression analyses and luciferase bioassay. Results: Four cases (3 CH and 1 IMH) consistent with BLT syndrome were identified. Two children were affected with respiratory distress and CH, but wild-type NKX2-1 gene. The remaining two presented choreic movements and no pulmonary involvement, but discrepant thyroid phenotypes: one had severe CH with lingual ectopy and the other one IMH with gland in situ. They were carriers of new de novo heterozygous frameshift mutations of NKX2-1 (c.177delG and c.153_166del14). The c.177delG leads to a prematurely truncated protein (p.H60TfsX11) with undetectable activity in vitro. The c.153_166del14 leads to the generation of an elongated aberrant protein (p.A52RfsX351) able to translocate into the nucleus, but completely inactive on a responsive promoter. Conclusions: Two novel heterozygous frameshift mutations of NKX2-1 were identified in 2 cases selected on the basis of a BLT-like phenotype among 183 hypothyroid infants. The atypical hypothyroid phenotypes of these 2 children (CH with lingual ectopy or IMH of postnatal onset) further expand the clinical spectrum that can be associated with NKX2-1 mutations.

Mild TSH resistance: clinical and hormonal features in childhood and adulthood

Mutations in TSH receptor (TSHR) are associated with TSH resistance, a genetic defect characterized by a heterogeneous phenotype ranging from severe hypothyroidism to subclinical hypothyroidism (SCH). We assessed the clinical and hormonal pattern of TSHR variants in a series of pediatric patients, and the long‐term outcome of growth, biochemical measurements of metabolism, and neuropsychological functions in TSHR mutations carriers.

Vitamin D dependent rickets, diagnostic and therapeutic difficulties: two case reports

Abstract There are two types of vitamin D dependent rickets (VDDR) that cause rickets in children. Vitamin D dependent rickets type 1 (VDDR-I) is caused by an inborn error of vitamin D metabolism, which interferes with renal conversion of calcidiol (25OHD) to calcitriol (1,25(OH)2D) by the enzyme 1α-hydroxylase. Vitamin D dependent rickets type 2 (VDDR-II) is caused by a defect in the vitamin D receptor (VDR). We report cases of two African children affected by VDDR-I and VDDR-II, respectively. Establishing an early diagnosis of these genetic forms of rickets is challenging, especially in developing countries where nutritional rickets (NR) is the most common variety of the disease. A prompt diagnosis is necessary to initiate adequate treatment, resolve biochemical features and prevent complications, such as severe deformities that may require surgical intervention.

Rare cases of autoimmune hypothyroidism in young children

Abstract Acquired autoimmune hypothyroidism is common in late childhood and adolescence but is very rare in the first 3 years of life. We report on three cases of autoimmune thyroiditis (AT) in young children who presented with constipation, decreased appetite, and increased hours of sleep. Our cases highlight that AT may remain undiagnosed for a long time in young children owing to the rarity of the disease.

Contents Vol. 3, 2014

Maria Alevizaki, Athens Ana Aranda, Madrid Rebecca Bahn, Rochester, Minn. Paul Banga, London Luigi Bartalena, Varese Bernadette Biondi, Naples Anita Boelen, Amsterdam Georg Brabant, Lübeck Henning Dralle, Halle Creswell J. Eastman, Westmead, N.S.W. Murat Erdogan, Ankara Valentin Fadeyev, Moscow Ulla Feldt-Rasmussen, Copenhagen Laszlo Hegedus, Odense George J. Kahaly, Mainz Rui Maciel, São Paolo Ana Luiza Maia, Porto Alegre Jens Mittag, Stockholm Ralf Paschke, Leipzig Simon Pearce, Newcastle-upon-Tyne Robin Peeters, Rotterdam Kris Poppe, Bruxelles Samuel Refetoff , Chicago, Ill. Jacques Samarut, Lyon Pilar Santisteban, Madrid YoungKee Shong, Seoul Jan Smit, Leiden Weiping Teng, Shenyang Mark Vanderpump, London Th eo Visser, Rotterdam Paolo Vitti, Pisa Graham Williams, London Shunichi Yamashita, Nagasaki Mariastella Zannini, Naples Luca Persani, Milan (Translational Th yroidology)