X-linked Hypophosphatemic Rickets, del(2)(q37.1;q37.3) Deletion Syndrome and Mosaic Turner Syndrome, mos 45,X/46,X, del(2)(q37.1;q37.3) in a 3-year-old Female

Two De Novo Mosaic Variants Within the Same Site of PHEX Gene in a Girl with X-Linked Hypophosphatemic Rickets

X-linked hypophosphatemic rickets (XLH) is the most common form of hypophosphatemic rickets, which is caused by the deficiencies of PHEX gene with an X-linked dominant inheritance pattern. As at least several thousands of XLH patients have been diagnosed, only several males and fewer females with mosaicism of PHEX gene were found. Here we describe an XLH girl with two de novo mosaic variants within the same site of PHEX gene. To rapidly screen all of the causative genes of hypophosphatemic rickets and rule out other diseases, DNA samples were initially analyzed using whole exome sequencing (WES). Interestingly, two different pathogenic mosaic variants, a known c.1809G > A(p.W603*) variant and a novel c.1809G > T(p.W603C) variant within the same site of PHEX gene, were identified in the proband by WES. Subsequent Sanger sequencing confirmed the presence and de novo pattern of these two mosaic variants in the proband, which were absent in her healthy parents. This is the first case to report two different mosaic variants of PHEX gene in an XLH individual. This XLH girl has a de novo mosaic genotype of c.1809 = /G > T/G > A in PHEX gene. Our report adds an unusual mocaicism case for XLH and expands the mutational event and spectrum of PHEX gene. Our report also alerts clinicians and geneticists to be cautious about mocaicism and detection methods.

Molecular Diagnoses of X-Linked and Other Genetic Hypophosphatemias: Results From a Sponsored Genetic Testing Program

X-linked hypophosphatemia (XLH), a dominant disorder caused by pathogenic variants in the PHEX gene, affects both sexes of all ages and results in elevated serum fibroblast growth factor 23 (FGF23) and below-normal serum phosphate. In XLH, rickets, osteomalacia, short stature, and lower limb deformity may be present with muscle pain and/or weakness/fatigue, bone pain, joint pain/stiffness, hearing difficulty, enthesopathy, osteoarthritis, and dental abscesses. Invitae and Ultragenyx collaborated to provide a no-charge sponsored testing program using a 13-gene next-generation sequencing panel to confirm clinical XLH or aid diagnosis of suspected XLH/other genetic hypophosphatemia. Individuals aged ≥6 months with clinical XLH or suspected genetic hypophosphatemia were eligible. Of 831 unrelated individuals tested between February 2019 and June 2020 in this cross-sectional study, 519 (62.5%) individuals had a pathogenic or likely pathogenic variant in PHEX (PHEX-positive). Among the 312 PHEX-negative individuals, 38 received molecular diagnoses in other genes, including ALPL, CYP27B1, ENPP1, and FGF23; the remaining 274 did not have a molecular diagnosis. Among 319 patients with a provider-reported clinical diagnosis of XLH, 88.7% (n = 283) had a reportable PHEX variant; 81.5% (n = 260) were PHEX-positive. The most common variant among PHEX-positive individuals was an allele with both the gain of exons 13-15 and c.*231A>G (3'UTR variant) (n = 66/519). Importantly, over 80% of copy number variants would have been missed by traditional microarray analysis. A positive molecular diagnosis in 41 probands (4.9%; 29 PHEX positive, 12 non-PHEX positive) resulted in at least one family member receiving family testing. Additional clinical or family member information resulted in variant(s) of uncertain significance (VUS) reclassification to pathogenic/likely pathogenic (P/LP) in 48 individuals, highlighting the importance of segregation and clinical data. In one of the largest XLH genetic studies to date, 65 novel PHEX variants were identified and a high XLH diagnostic yield demonstrated broad insight into the genetic basis of XLH. © 2021 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Clinical case report: A case of Turner syndrome with Graves' disease

INTRODUCTION

The incidence of Hashimoto's thyroiditis among patients who have Turner syndrome (TS) has increased, but Graves' disease (GD) in patients with TS is rarely reported. Here we report a rare case of TS with GD accompanied by hypogonadotropic hypogonadism.

PATIENT CONCERNS

We report the case of a 16-year-old girl who complained nervousness, fatigue, marasmus, heat intolerance, sweating, palpitation, and tremor lasting for more than a month. She had no medical history.

DIAGNOSIS

TS was diagnosed of the results of karyotyping demonstrated a gene karyotype of 46, X, i (X)(q10). GD was also diagnosed in this patient following the detection of thyroid function analysis.

INTERVENTIONS

Methimazole was administered after identification of GD. Due to the absence of secondary sex characteristics, the patient was given a conjugated estrogen preparation for 1 year, followed by the addition of estradiol cyproterone tablets for the onset of menstruation.

OUTCOMES

The hyperthyroidism symptoms of the patient had improved both clinically and laboratory tests after methimazole therapy. She was treated with estrogen and estradiol cyproterone, and the uterus and secondary sexual characteristics of the patient developed during 1 year follow-up.

CONCLUSION

TS generally presents as hypergonadotropic hypogonadism. However, hypogonadotropic hypogonadism cannot completely exclude TS. The diagnosis of this disease depends on chromosomal examination. The disease should be detected and treated as early as possible to improve life quality of the patient.

Dual diagnoses in 152 patients with Turner syndrome: Knowledge of the second condition may lead to modification of treatment and/or surveillance

Turner syndrome is a sex chromosome abnormality in which a female has a single X chromosome or structurally deficient second sex chromosome. The phenotypic spectrum is broad, and atypical features prompt discussion of whether the known features of Turner syndrome should be further expanded. With the advent of clinical whole exome sequencing, there has been increased realization that some patients with genetic disorders carry a second genetic disorder, leading us to hypothesize that a "dual diagnosis" may be more common than suspected for Turner syndrome. We report five new patients with Turner syndrome and a co-occurring genetic disorder including one patient with Li-Fraumeni syndrome, Li-Fraumeni and Noonan syndrome, mosaic trisomy 8, pathogenic variant in RERE, and blepharophimosis-ptosis-epicanthanus inversus syndrome. We also undertook an extensive literature review of 147 reports of patients with Turner syndrome and a second genetic condition. A total of 47 patients (31%) had trisomy 21, followed by 36 patients (24%) had one of 11 X-linked disorders. Notably, 80% of the 147 reported patients with a dual diagnosis had mosaicism for Turner syndrome, approximately twice the frequency in the general Turner syndrome population. This article demonstrates the potential for co-occurring syndromes in patients with Turner syndrome, prompting us to recommend a search for an additional genetic disorder in Turner patients with unusual features. Knowledge of the second condition may lead to modification of treatment and/or surveillance. We anticipate that increased awareness and improved diagnostic technologies will lead to the identification of more cases of Turner syndrome with a co-occurring genetic syndrome.