Second 46,XX male with MLS syndrome

Prevalence and Clustering of Congenital Heart Defects Among Boys With Hypospadias

IMPORTANCE

Hypospadias is a common birth defect of the male urinary tract that may be isolated or may co-occur with other structural malformations, including congenital heart defects (CHDs). The risk for co-occurring CHDs among boys with hypospadias remains unknown, which limits screening and genetic testing strategies.

OBJECTIVE

To characterize the risk of major CHDs among boys born with hypospadias.

DESIGN, SETTING, AND PARTICIPANTS

This retrospective cohort study used data from population-based birth defect surveillance programs on all male infants born in 11 US states from January 1, 1995, to December 31, 2014. Statistical analysis was performed from September 2, 2020, to March 25, 2022.

EXPOSURE

Hypospadias.

MAIN OUTCOMES AND MEASURES

Demographic and diagnostic data were obtained from 2 active state-based birth defect surveillance programs for primary analyses, the Texas Birth Defects Registry and the Arkansas Reproductive Health Monitoring System, with validation among 9 additional states in the National Birth Defects Prevention Network (NBDPN). Birth defect diagnoses were identified using the British Pediatric Association coding for hypospadias (exposure) and major CHDs (primary outcomes). Maternal covariates and birth year were also abstracted from the vital records. Poisson regression was used to estimate adjusted prevalence ratios and 95% CIs for major CHDs within Texas and Arkansas and combined using inverse variance-weighted meta-analysis. Findings were validated using the NBDPN.

RESULTS

Among 3.7 million pregnancies in Texas and Arkansas, 1485 boys had hypospadias and a co-occurring CHD. Boys with hypospadias were 5.8 times (95% CI, 5.5-6.1) more likely to have a co-occurring CHD compared with boys without hypospadias. Associations were observed for every specific CHD analyzed among boys with hypospadias, occurred outside of chromosomal anomalies, and were validated in the NBDPN. An estimated 7.024% (95% CI, 7.020%-7.028%) of boys with hypospadias in Texas and 5.503% (95% CI, 5.495%-5.511%) of boys with hypospadias in Arkansas have a co-occurring CHD. In addition, hypospadias severity and maternal race and ethnicity were independently associated with the likelihood for hypospadias to co-occur with a CHD; boys in Texas with third-degree (ie, more severe) hypospadias were 2.7 times (95% CI, 2.2-3.4) more likely than boys with first-degree hypospadias to have a co-occurring CHD, with consistent estimates in Arkansas (odds ratio, 2.7; 95% CI, 1.4-5.3), and boys with hypospadias born to Hispanic mothers in Texas were 1.5 times (95% CI, 1.3-1.8) more likely to have a co-occurring CHD than boys with hypospadias born to non-Hispanic White mothers.

CONCLUSIONS AND RELEVANCE

In this cohort study, boys with hypospadias had a higher prevalence of CHDs than boys without hypospadias. These findings support the need for consideration of additional CHD screening programs for boys born with hypospadias.

Linear Skin Defects with Multiple Congenital Anomalies (LSDMCA): An Unconventional Mitochondrial Disorder

Mitochondrial disorders, although heterogeneous, are traditionally described as conditions characterized by encephalomyopathy, hypotonia, and progressive postnatal organ failure. Here, we provide a systematic review of Linear Skin Defects with Multiple Congenital Anomalies (LSDMCA), a rare, unconventional mitochondrial disorder which presents as a developmental disease; its main clinical features include microphthalmia with different degrees of severity, linear skin lesions, and central nervous system malformations. The molecular basis of this disorder has been elusive for several years. Mutations were eventually identified in three X-linked genes, i.e., HCCS, COX7B, and NDUFB11, which are all endowed with defined roles in the mitochondrial respiratory chain. A peculiar feature of this condition is its inheritance pattern: X-linked dominant male-lethal. Only female or XX male individuals can be observed, implying that nullisomy for these genes is incompatible with normal embryonic development in mammals. All three genes undergo X-inactivation that, according to our hypothesis, may contribute to the extreme variable expressivity observed in this condition. We propose that mitochondrial dysfunction should be considered as an underlying cause in developmental disorders. Moreover, LSDMCA should be taken into consideration by clinicians when dealing with patients with microphthalmia with or without associated skin phenotypes.

Clinical spectrum of females with HCCS mutation: from no clinical signs to a neonatal lethal form of the microphthalmia with linear skin defects (MLS) syndrome

BACKGROUND

Segmental Xp22.2 monosomy or a heterozygous HCCS mutation is associated with the microphthalmia with linear skin defects (MLS) or MIDAS (microphthalmia, dermal aplasia, and sclerocornea) syndrome, an X-linked disorder with male lethality. HCCS encodes the holocytochrome c-type synthase involved in mitochondrial oxidative phosphorylation (OXPHOS) and programmed cell death.

METHODS

We characterized the X-chromosomal abnormality encompassing HCCS or an intragenic mutation in this gene in six new female patients with an MLS phenotype by cytogenetic analysis, fluorescence in situ hybridization, sequencing, and quantitative real-time PCR. The X chromosome inactivation (XCI) pattern was determined and clinical data of the patients were reviewed.

RESULTS

Two terminal Xp deletions of ≥ 11.2 Mb, two submicroscopic copy number losses, one of ~850 kb and one of ≥ 3 Mb, all covering HCCS, 1 nonsense, and one mosaic 2-bp deletion in HCCS are reported. All females had a completely (>98:2) or slightly skewed (82:18) XCI pattern. The most consistent clinical features were microphthalmia/anophthalmia and sclerocornea/corneal opacity in all patients and congenital linear skin defects in 4/6. Additional manifestations included various ocular anomalies, cardiac defects, brain imaging abnormalities, microcephaly, postnatal growth retardation, and facial dysmorphism. However, no obvious clinical sign was observed in three female carriers who were relatives of one patient.

CONCLUSION

Our findings showed a wide phenotypic spectrum ranging from asymptomatic females with an HCCS mutation to patients with a neonatal lethal MLS form. Somatic mosaicism and the different ability of embryonic cells to cope with an OXPHOS defect and/or enhanced cell death upon HCCS deficiency likely underlie the great variability in phenotypes.

Corneal pathology in microphthalmia with linear skin defects syndrome

PURPOSE

To describe the histopathology of the cornea in microphthalmia with linear streaks (MLS) syndrome.

METHODS

Two patients with MLS syndrome underwent penetrating keratoplasty. This study describes the histopathology and investigates immunophenotype of the corneal extracellular matrix by using keratan sulfate and collagen type III antibodies.

RESULTS

Clinical examination revealed bilateral sclerocornea and characteristic skin changes. By light microscopy, central corneal stroma in both patients showed vascularization and irregular thick collagen lamellae typical of sclerocornea. In addition, corneal thinning, anterior synechiae, and the absence of the Descemet membrane were noted, which was suggestive of Peters anomaly. Diffuse and intense anti-keratan sulfate staining and minimal anti-collagen type III stromal staining were seen in both corneal buttons.

CONCLUSIONS

The cornea in MLS may clinically resemble sclerocornea. Histologic features resemble those previously described in sclerocornea and also seen in anterior segment dysgeneses. Keratan sulfate and collagen type III labeling suggests that the corneal extracellular matrix resembled cornea and not sclera.

Mother and daughter with a terminal Xp deletion: implication of chromosomal mosaicism and X-inactivation in the high clinical variability of the microphthalmia with linear skin defects (MLS) syndrome

The microphthalmia with linear skin defects (MLS or MIDAS) syndrome is a rare X-linked dominant inherited disorder with male lethality, associated with segmental aneuploidy of the Xp22.2 region in most of the cases. However, we recently described heterozygous sequence alterations in a single gene, HCCS, in females with MLS. Beside the classical MLS phenotype, occasional features such as sclerocornea, agenesis of the corpus callosum, and congenital heart defects can occur. Although the majority of cases are sporadic, mother-to-daughter transmission has been observed and a high intra- and interfamilial phenotypic variability exists. We describe an asymptomatic mother and her daughter presenting with the typical features of MLS syndrome. By cytogenetic analysis both females were found to have a terminal Xp deletion with the breakpoint in Xp22.2, mapping near to or within the MSL3L1 gene which is located centromeric to HCCS. FISH analysis revealed that the mother is a mosaic with 45,X(11)/46,X,del(X)(p22.2)(89), while in all cells of the MLS-affected daughter a hybridization pattern consistent with a 46,X,del(X)(p22.2) karyotype was detected. By haplotype analysis we identified the paternal X chromosome of the mother to carry the terminal Xp deletion. X-inactivation studies showed a completely skewed pattern in mother and daughter with the deleted X chromosome to be preferentially inactivated in their peripheral blood cells. We suggest that both chromosomal mosaicism as well as functional X chromosome mosaicism could contribute to the lack of any typical MLS feature in individuals with a heterozygous MLS-associated mutation. The 45,X cell population, that most likely is also present in other tissues of the mother, might have protected her from developing MLS. Nonetheless, a non-random X-inactivation pattern in favor of activity of the wild-type X chromosome in the early blastocyte could also account for the apparent lack of any disease sign in this female.

Microphthalmia with linear skin defects (MLS) syndrome evaluated by prenatal karyotyping, FISH and array comparative genomic hybridization

OBJECTIVE

To explore the utility of comparative genomic hybridization to BAC arrays (array CGH) for prenatal diagnosis of microphthalmia and linear skin defects syndrome.

METHODS

We used karyotype analysis, FISH and array CGH to investigate an X;Y translocation. Replication studies were done on cultured amniocytes and lymphoblasts.

RESULTS

We describe a severe case of MLS syndrome that presented prenatally with multiple anomalies including cystic hygroma, microphthalmia, intrauterine growth restriction and a complex congenital heart defect. Cytogenetic analysis of amniocytes revealed an unbalanced de novo translocation between chromosomes X and Y [karyotype 46,X,der(X)t(X;Y)(p22.3;q11.2).ish der(X)(DXZ1+,DMD+,KAL-,STS-,SRY-),22q11.2 (Tuple1 x 2)]. MLS diagnosis was made at birth and the prenatal karyotype was confirmed. Replication studies showed the derivative X chromosome was the inactive X. Array CGH confirmed the X and Y imbalances seen in the karyotype and also showed twelve BACs in the MLS region were deleted as a result of the translocation. FISH with BAC clones verified the array findings and placed the X breakpoint in Xp22.2, resulting in the amended karyotype, 46,X,der(X)t(X;Y)(p22.2;q11.2).ish der(X)(DXZ1+,DMD+,KAL-,STS-,SRY-),22q11.2(Tuple1 x 2) arr cgh Xp22.33p22.2(LLNOYCO3M15D10 -->GS1-590J6)x 1,Yq11.222q23(RP11-20H21-->RP11-79J10)x 1.

CONCLUSION

The sensitivity of array CGH was valuable in detecting monosomy of the MLS critical region. Array CGH should be considered for the prenatal diagnosis of this syndrome.

Microphthalmia with linear skin defects (MLS) syndrome: Clinical, cytogenetic, and molecular characterization of 11 cases

The microphthalmia with linear skin defects (MLS) syndrome (MIM 309801) is a severe and rare developmental disorder, which is inherited as an X-linked dominant trait with male lethality. In the vast majority of patients, this syndrome is associated with terminal deletion of the Xp22.3 region. Thirty-five cases have been described to date in the literature since the first description of the syndrome in the early 1990s. We now report on the clinical, cytogenetic, and molecular characterization of 11 patients, 7 of whom have not been described previously. Seven of these patients have chromosomal abnormalities of the short arm of the X-chromosome, which were characterized and defined by fluorescence in situ hybridization (FISH) analysis. Intriguingly, one of the patients displays an interstitial Xp22.3 deletion, which to the best of our knowledge is the first reported for this condition. Finally we report on the identification and molecular characterization of four cases with clinical features of MLS but apparently normal karyotypes, verified by FISH analysis using genomic clones spanning the MLS minimal critical region, and with genome-wide analysis using a 1 Mb resolution BAC microarray. These patients made it possible to undertake mutation screening of candidate genes and may prove critical for the identification of the gene responsible for this challenging and intriguing genetic disease.

Microphthalmia with linear skin defects syndrome (MLS): a male with a mosaic paracentric inversion of Xp

The microphthalmia with linear skin defects syndrome (MLS) is an X-linked dominant disorder with male lethality. In the majority of the patients reported, the MLS syndrome is caused by segmental monosomy of the Xp22.3 region. To date, five male patients with MLS and 46,XX karyotype ("XX males") have been described. Here we report on the first male case with MLS and an XY complement. The patient showed agenesis of the corpus callosum, histiocytoid cardiomyopathy, and lactic acidosis but no microphthalmia, and carried a mosaic subtle inversion of the short arm of the X chromosome in 15% of his peripheral blood lymphocytes, 46,Y,inv(X)(p22.13 approximately 22.2p22.32 approximately 22.33)[49]/46,XY[271]. By fluorescence IN SITU hybridization (FISH), we showed that YAC 225H10 spans the breakpoint in Xp22.3. End-sequencing and database analysis revealed a YAC insert of at least 416 kb containing the genes HCCS and AMELX, and exons 2-16 of ARHGAP6. Molecular cytogenetic data suggest that the Xp22.3 inversion breakpoint is located in intron 1 of ARHGAP6, the gene encoding the Rho GTPase activating protein 6. Future molecular studies in karyotypically normal female MLS patients to detect submicroscopic rearrangements including the ARHGAP6 gene as well as mutation screening of ARHGAP6 in patients with no obvious chromosomal rearrangements will clarify the role of this gene in MLS syndrome.

Microphthalmia with linear skin defects (MLS), Aicardi, and Goltz syndromes: are they related X-linked dominant male-lethal disorders?

Gene identification for X-linked dominant sporadic disorders is challenging because no extended families exist that can be studied by linkage analysis. Therefore, classic positional cloning approaches are not possible, and other methods have to be used to search for candidate genes. These conditions present the next challenge for disease-gene identification of Mendelian disorders. The various issues and difficulties involved, such as male lethality, X chromosome inactivation, and analysis of phenotypic similarities among different conditions are illustrated through discussion of three X-linked developmental disorders: microphthalmia with linear skin defects (MLS) syndrome, Aicardi syndrome, and Goltz syndrome (focal dermal hypoplasia).

Twin brothers with MIDAS syndrome and XX karyotype

Twin brothers with microphthalmia, facial dermal hypoplasia, sclerocornea, and supraventricular tachycardia, are reported. Their clinical features are compatible with MIDAS syndrome, a known X-linked and hemizygous male lethal condition. Their karyotypes showed an XX sex chromosome modality with a subtle Xp/Yp translocation proven by the presence of SRY gene. The pregnancy was complicated with fetal supraventricular tachycardia, which was treated with digoxin prenatally. Postnatally, both twins required treatment with adenosine, digoxin, and propanolol to remain in normal sinus rhythm. The possible involvement of the heart, only in the form of cardiomyopathy with arrhythmia is emphasized. Both twins had a selective X-inactivation of the derivative chromosome X with Xp/Yp translocation.

[Cutaneous aplasia, non compaction of the left ventricle and severe cardiac arrhythmia: a new case of MLS syndrome (microphtalmia with linear skin defects)]

A female neonate presented with cutaneous aplasia located to the face and the neck associated with a non compaction of the left ventricle leading to the diagnosis of MLS syndrome (microphtalmia with linear skin defects). The follow-up was complicated by life-threatening cardiac arrhythmia underlying prevention by an early diagnosis and adequate care. MLS syndrome and non compaction of myocardium are both located on X chromosome.

Xp22.3 microdeletion in a 19-year-old girl with clinical features of MLS syndrome

We describe a 19-year-old girl who has clinical features of microphthalmia with linear skin defects (MLS) syndrome caused by a microdeletion of Xp22.3. In addition to the classical ocular abnormalities and linear skin defects she has other features not previously described. She was previously reported in this journal in 1990 as poikiloderma congenitale, but her true diagnosis of an Xp22.3 microdeletion was clarified when fluorescent in situ hybridization (FISH) analysis indicated that one of her X chromosomes had a microdeletion including the KAL gene. We describe this patient with an Xp22.3 microdeletion to heighten awareness among dermatologists of this syndrome and to underscore the difficulties in diagnosing MLS syndrome.

Corpus callosum agenesis, multiple cysts, skin defects, and subtle ocular abnormalities with a de novo mutation [45,XX,der(5), t(5;;14) (pter;q11.2)]

We report on a 2-year-old girl with a de novo mutation [45,XX,der(5),t(5;14) (pter;q11.2)] with corpus callosum agenesis, multiple cysts (cerebral and cardiac), subtle eye abnormalities, and at least two different skin defects, strongly indicating neuroectodermal involvement, as a neuromuscular choristoma (hamartoma) and an eccrine hamartoma. Fluorescent in situ hybridization with different single-locus probes showed that chromosome 5 has a very small deletion, confined to a region composed of repetitive sequences. By contrast, the long (q) arm of chromosome 14 seems to be much more involved in the rearrangement, with partial monosomy spanning from the centromere to the D14S72 and D14S261 loci. The extent of the deleted region of chromosome 14 is approximately 16 cM. To our knowledge, this is the smallest reported deletion involving the chromosome 14q11.2 region to be associated with a developmental disorder resulting in variable eye, skin, and brain anomalies. We suggest that a new syndrome, mimicking in some ways the MLS phenotype, is caused by a deletion in the chromosome 14q11.2 region.