Alert for the high prevalence of vitamin D deficiency in adolescents in a large Brazilian sample.

OBJECTIVE: To estimate the prevalence of vitamin D deficiency and severe deficiency in children and adolescents, in a large Brazilian sample. METHODOLOGY: Results of 413,976 25(OH)D measurements in children and adolescents aged 0 to 18 years collected between 01/2014 and 10/2018 were obtained from the database of a Clinical Laboratory. In this population, 25 hydroxyvitamin D concentrations below 20 ng/mL are considered deficient, and below 12 ng/mL as severe deficiency. All measurements were performed by immunoassay and the results were distributed by gender, age group, seasonality, and latitude. RESULTS: The mean of 25(OH)D levels was 29.2 ng/mL with a standard deviation of 9.2 ng/mL. Of the total samples, 0.8% had a concentration < 12 ng/mL, and 12.5% of the samples had a concentration < 20 ng/mL, with a higher prevalence in females. Children under 2 years of age had the lowest prevalence. The effects of latitude and seasonality were quite evident. In samples of female adolescents from the southern region in winter, 36% of vitamin D deficiency and 5% of severe deficiency were found. CONCLUSION: In this large number of measurements of 25(OH)D in children and adolescents, 12.5% had a deficiency and 0.8% had severe deficiency. A greater deficiency was observed among adolescents, especially females, which raises questions about the need for supplementation during this period of life.

Hypomagnesemia with Hypercalciuria Leading to Nephrocalcinosis, Amelogenesis Imperfecta, and Short Stature in a Child Carrying a Homozygous Deletion in the CLDN16 Gene.

Familial hypomagnesemia with hypercalciuria and nephrocalcinosis (FHHNC) is a rare autosomal recessive disease caused by mutations in the CLDN16 or CLDN19 gene; however, few cases develop classical amelogenesis imperfecta. Herein, we report the case of a boy with early clinical renal manifestations that started at 1 year of age and presenting with dental hypoplasia and growth delay. The patient presented with vomiting, polyuria, and polydipsia. Apart from recurrent sterile leukocyturia, erroneously treated as infectious, he was normal, except for short stature and amelogenesis imperfecta with gradually discolored teeth. Laboratory tests revealed hyperparathyroidism, hypomagnesemia, severe hypercalciuria, and hypermagnesuria on 24-h urine testing. Helical computed tomography confirmed nephrocalcinosis. We performed whole-exome sequencing (WES) to test the hypothesis of FHHNC and oligogenic inheritance of amelogenesis. Analysis of the WES binary sequence alignment/map file revealed the presence of exon 1 of the CLDN16 and absence of the other exons [c.325_c918*? (E2_E5del)]. We confirmed a CLDN16 E2_E5 homozygous deletion by multiplex ligation-dependent probe amplification and polymerase chain reaction assays. Although most mutations causing FHHNC are missense and nonsense mutations in the CLDN16 or CLDN19 gene, large deletions occur and may be misled by WES, which is generally used for genetic screening of oligogenic disorders. The patient received cholecalciferol, magnesium oxide and potassium citrate. Later, the combination with hydrochlorothiazide plus amiloride was prescribed, with a good response during follow-up. Our report broadens the phenotype of FHHNC, including severe early-onset amelogenesis and short stature, and reinforces the phenotype-genotype correlation of the large deletion found in CLDN16.

Novel mutation in MCT8 gene in a Brazilian boy with thyroid hormone resistance and severe neurologic abnormalities.

MCT8 is a cellular transporter of thyroid hormones important in their action and metabolization. We report a male patient with the novel inactivating mutation 630insG in the coding region in exon 1 of MCT8. He was characterized clinically by severe neurologic impairment (initially with global hypotonia, later evolving with generalized hypertonia), normal growth during infancy, reduced weight gain, and absence of typical signs and symptoms of hypothyroidism, while the laboratory evaluation disclosed elevated T3, low total and free T4, and mildly elevated TSH serum levels. Treatment with levothyroxine improved thyroid hormone profile but was not able to alter the clinical picture of the patient. These data reinforce the concept that the role of MCT8 is tissue-dependent: while neurons are highly dependent on MCT8, bone tissue, adipose tissue, muscle, and liver are less dependent on MCT8 and, therefore, may suffer the consequences of the exposition to high serum T3 levels.

Novel mutation in MCT8 gene in a Brazilian boy with thyroid hormone resistance and severe neurologic abnormalities / Mutação nova do gene MCT8 em menino Brasileiro com resistência ao hormônio tireioidiano e neuropatia grave

O MCT8 é um transportador celular de hormônios tireoidianos, importante para sua ação e metabolização. Relatamos o caso de um menino com a nova mutação inativadora 630insG no éxon 1 do MCT8. O paciente caracterizou-se por grave comprometimento neurológico (inicialmente com hipotonia global, evoluindo com hipertonia generalizada), crescimento normal nos dois primeiros anos de vida, reduzido ganho ponderal e ausência dos sinais e sintomas típicos de hipotireoidismo. A sua avaliação sérica revelou elevação do T3, redução do T4 total e livre e TSH levemente aumentado. O tratamento com levotiroxina melhorou o perfil hormonal tireoidiano, mas não modificou o quadro clínico do paciente. Esses dados reforçam o conceito de que o papel do MCT8 é tecido-dependente: enquanto os neurônios são altamente dependentes do MCT8, o osso, o tecido adiposo, o músculo e o fígado são menos dependentes do MCT8 e, portanto, podem sofrer as consequências da exposição a níveis séricos elevados de T3.

MCT8 is a cellular transporter of thyroid hormones important in their action and metabolization. We report a male patient with the novel inactivating mutation 630insG in the coding region in exon 1 of MCT8. He was characterized clinically by severe neurologic impairment (initially with global hypotonia, later evolving with generalized hypertonia), normal growth during infancy, reduced weight gain, and absence of typical signs and symptoms of hypothyroidism, while the laboratory evaluation disclosed elevated T3, low total and free T4, and mildly elevated TSH serum levels. Treatment with levothyroxine improved thyroid hormone profile but was not able to alter the clinical picture of the patient. These data reinforce the concept that the role of MCT8 is tissue-dependent: while neurons are highly dependent on MCT8, bone tissue, adipose tissue, muscle, and liver are less dependent on MCT8 and, therefore, may suffer the consequences of the exposition to high serum T3 levels.

Glibenclamide unresponsiveness in a Brazilian child with permanent neonatal diabetes mellitus and DEND syndrome due to a C166Y mutation in KCNJ11 (Kir6.2) gene / Falha de resposta à glibenclamida em criança brasileira com diabetes melito neonatal permanente e síndrome DEND devido a mutação C166Y no gene KCNJ11 (Kir6.2)

Heterozygous activating mutations of KCNJ11 (Kir6.2) are the most common cause of permanent neonatal diabetes mellitus (PNDM) and several cases have been successfully treated with oral sulfonylureas. We report on the attempted transfer of insulin therapy to glibenclamide in a 4-year old child with PNDM and DEND syndrome, bearing a C166Y mutation in KCNJ11. An inpatient transition from subcutaneous NPH insulin (0.2 units/kg/d) to oral glibenclamide (1 mg/kg/d and 1.5 mg/kg/d) was performed. Glucose and C-peptide responses stimulated by oral glucose tolerance test (OGTT), hemoglobin A1c levels, the 8-point self-measured blood glucose (SMBG) profile and the frequency of hypoglycemia episodes were analyzed, before and during treatment with glibenclamide. Neither diabetes control nor neurological improvements were observed. We concluded that C166Y mutation was associated with a form of PNDM insensitive to glibenclamide.

As mutações ativadoras, heterozigóticas do gene KCNJ11 (Kir6.2) são a causa mais freqüente de diabetes melito neonatal permanente (DMNP) e a terapêutica oral com sulfoniluréias tem sido bem sucedida em muitos destes casos. Relatamos o processo de substituição da insulinoterapia convencional para o tratamento oral com glibenclamida em uma paciente de 4 anos, portadora de DMNP e síndrome DEND devido a uma mutação C166Y no gene KCNJ11. A insulina NPH (0,2 U/kg/dia) foi substituída pela glibenclamida (1 mg/kg/dia e 1,5 mg/kg/dia) durante internação hospitalar. As respostas de glicose e peptídeo-C no teste de tolerância oral à glicose (OGTT), os níveis de hemoglobina glicada, o perfil de glicemias capilares de 8 pontos e a freqüência de hipoglicemias foram comparados antes e durante o tratamento com glibenclamida. Não houve melhora no controle glicêmico, nem no quadro neurológico. Concluímos que a mutação C166Y associa-se a uma forma de DMNP insensível à glibenclamida.

Glibenclamide unresponsiveness in a Brazilian child with permanent neonatal diabetes mellitus and DEND syndrome due to a C166Y mutation in KCNJ11 (Kir6.2) gene.

Heterozygous activating mutations of KCNJ11 (Kir6.2) are the most common cause of permanent neonatal diabetes mellitus (PNDM) and several cases have been successfully treated with oral sulfonylureas. We report on the attempted transfer of insulin therapy to glibenclamide in a 4-year old child with PNDM and DEND syndrome, bearing a C166Y mutation in KCNJ11. An inpatient transition from subcutaneous NPH insulin (0.2 units/kg/d) to oral glibenclamide (1 mg/kg/d and 1.5 mg/kg/d) was performed. Glucose and C-peptide responses stimulated by oral glucose tolerance test (OGTT), hemoglobin A1c levels, the 8-point self-measured blood glucose (SMBG) profile and the frequency of hypoglycemia episodes were analyzed, before and during treatment with glibenclamide. Neither diabetes control nor neurological improvements were observed. We concluded that C166Y mutation was associated with a form of PNDM insensitive to glibenclamide.