Craniofacial and dental manifestations of triple X syndrome associated with congenital hypothyroidism: a case report

Unusual Trisomy X Phenotype Associated with a Concurrent Heterozygous 16p11.2 Deletion: Importance of an Integral Approach for Proper Diagnosis

Trisomy X is the most frequent sex chromosome anomaly in women, but it is often underdiagnosed postnatally because most patients do not show any clinical manifestation. It is estimated that only 10% of patients with trisomy X are diagnosed by clinical findings. Thus, it has been proposed that the clinical spectrum is not yet fully delimited, and additional uncommon or atypical clinical manifestations could be related to this entity. The present report describes a female carrying trisomy X but presenting atypical manifestations, including severe intellectual disability, short stature, thymus hypoplasia, and congenital hypothyroidism (CH). These clinical findings were initially attributed to trisomy X. However, chromosome microarray analysis (CMA) subsequently revealed that the patient also bears a heterozygous 304-kb deletion at 16p11.2. This pathogenic copy-number variant (CNV) encompasses 13 genes, including TUFM. Some authors recommend that when a phenotype differs from that described for an identified microdeletion, the presence of pathogenic variants in the non-deleted allele should be considered to assess for an autosomal recessive disorder; thus, we used a panel of 697 genes to rule out a pathogenic variant in the non-deleted TUFM allele. We discuss the possible phenotypic modifications that might be related to an additional CNV in individuals with sex chromosome aneuploidy (SCA), as seen in our patient. The presence of karyotype-demonstrated trisomy X and CMA-identified 16p11.2 deletion highlights the importance of always correlating a patient's clinical phenotype with the results of genetic studies. When the phenotype includes unusual manifestations and/or exhibits discrepancies with that described in the literature, as exemplified by our patient, a more extensive analysis should be undertaken to enable a correct diagnosis that will support proper management, genetic counseling, and medical follow-up.

Do prenatal and postnatal hypothyroidism affect the craniofacial structure?: An experimental study

OBJECTIVE

To investigate the effect of experimental prenatal and postnatal hypothyroidism (HT) on the craniofacial structure in rats.

MATERIALS AND METHODS

Female Wistar albino rats were mated with males for fertilization. Pregnant rats were divided into three groups. Group 1 (methimazole [MMI]-induced prenatal hypothyroidism group) mother rats were given MMI water during and after pregnancy. Group 2 (MMI-induced postnatal hypothyroidism group) mother rats were given MMI water after pregnancy. After the breast-feeding period, group 1 and 2 rat pups received the same water as their lactating mothers drank. Group 3 (control group) pregnant rats and rat pups were given normal tap water. When the rat pups were 90 days of age, lateral cephalometric and posteroanterior films were taken under anesthesia.

RESULTS

Posteroanterior radiographs revealed that palatal, cranial, bizygomatic arch, and bigonial width measurements were significantly shorter in prenatal HT and postnatal HT groups compared to the control group (P < .001). Intragroup comparisons in lateral cephalometric radiographs showed that, nearly all of the comparisons were statistically significant (P < .05), with the exception of the Co-Gn, E-Pg/S-Gn measurements between the prenatal and postnatal HT groups.

CONCLUSIONS

Sagittal and transverse measurements showed that untreated HT has detrimental effects on the growth of the maxilla and mandible.