Distichiasis, congenital heart defects and mixed peripheral vascular anomalies

Refractive Amblyopia Secondary to Astigmatism in Pediatric Patients With Distichiasis

Distichiasis is the presence of accessory eyelashes emerging from the meibomian gland orifices. It may occur as an isolated abnormality or in conjunction with other ocular and systemic defects. Lymphedema-distichiasis syndrome (LDS) is an autosomal dominant disorder characterized by distichiasis and age-dependent lower extremity swelling due to altered lymphatic flow. The authors describe four pediatric patients with distichiasis (one with genetically proven LDS) with refractive amblyopia secondary to astigmatism. [J Pediatr Ophthalmol Strabismus. 2021;58(4);e16-e18.].

Spinal extradural arachnoid cysts in lymphedema-distichiasis syndrome

PURPOSE

Lymphedema-distichiasis syndrome is characterized by the presence of lower limb lymphedema and supernumerary eyelashes arising from the Meibomian glands. Spinal extradural arachnoid cysts have been observed in some families but their true frequency is unknown. The aim of this study is to determine the frequency of spinal extradural arachnoid cysts in lymphedema distichiasis syndrome.

METHODS

We collected clinical information from all 45 living members of a complete family of 48 members and performed molecular analysis of the FOXC2 gene in 30 individuals. We obtained spinal magnetic resonance imaging from all family members with a FOXC2 gene mutation.

RESULTS

Twelve family members carried a mutation in the FOXC2 gene and had clinical features of lymphedema-distichiasis syndrome. Of these, 58% (seven individuals) had extradural arachnoid cysts.

DISCUSSION

We suggest that a follow-up protocol for lymphedema-distichiasis syndrome families should include spinal magnetic resonance imaging for all affected members so that the timing of surgery for removal of these cysts can be optimized.

Post-thrombotic syndrome in children: a systematic review of frequency of occurrence, validity of outcome measures, and prognostic factors

BACKGROUND

Post-thrombotic syndrome is a manifestation of chronic venous insufficiency following deep venous thrombosis. This systematic review was conducted to critically evaluate pediatric evidence on frequency of occurrence, validity of outcome measures, and prognostic indicators of post-thrombotic syndrome.

DESIGN AND METHODS

A comprehensive literature search of original reports revealed 19 eligible studies, totaling 977 patients with upper/lower extremity deep venous thrombosis. Calculated weighted mean frequency of post-thrombotic syndrome was 26% (95% confidence interval: 23-28%) overall, and differed significantly by prospective/non-prospective analysis and use/non-use of a standardized outcome measure.

RESULTS

Standardized post-thrombotic syndrome outcome measures included an adaptation of the Villalta scale, the Clinical-Etiologic-Anatomic-Pathologic classification, and the Manco-Johnson instrument. Data on validity were reported only for the Manco-Johnson instrument. No publications on post-thrombotic syndrome-related quality of life outcomes were identified. Candidate prognostic factors for post-thrombotic syndrome in prospective studies included use/non-use of thrombolysis and plasma levels of factor VIII activity and D-dimer.

CONCLUSIONS

Given that affected children must endure chronic sequelae for many decades, it is imperative that future collaborative pediatric prospective cohort studies and trials assess as key objectives and outcomes the incidence, severity, prognostic indicators, and health impact of post-thrombotic syndrome, using validated measures.

Animal models for the molecular and mechanistic study of lymphatic biology and disease

The development of animal model systems for the study of the lymphatic system has resulted in an explosion of information regarding the mechanisms governing lymphatic development and the diseases associated with lymphatic dysfunction. Animal studies have led to a new molecular model of embryonic lymphatic vascular development, and have provided insight into the pathophysiology of both inherited and acquired lymphatic insufficiency. It has become apparent, however, that the importance of the lymphatic system to human disease extends, beyond its role in lymphedema, to many other diverse pathologic processes, including, very notably, inflammation and tumor lymphangiogenesis. Here, we have undertaken a systematic review of the models as they relate to molecular and functional characterization of the development, maturation, genetics, heritable and acquired diseases, and neoplastic implications of the lymphatic system. The translation of these advances into therapies for human diseases associated with lymphatic dysfunction will require the continued study of the lymphatic system through robust animal disease models that simulate their human counterparts.

A novel frameshift mutation of FOXC2 gene in a family with hereditary lymphedema-distichiasis syndrome associated with renal disease and diabetes mellitus

Lymphedema-distichiasis (LD) syndrome is a clinically variable autosomal dominant disorder. The disorder is caused by mutations in the forkhead transcription factor FOXC2 gene on chromosome band 16q24.3. Here, we report the sequence of the FOXC2 gene in a German-Irish family with LD in six affected relatives over three generations and identify a single adenine base pair insertion at nt 1006--1007. This insertion creates a frameshift mutation that predicts a premature stop at codon 462. In addition to LD, four of the affected family members have renal disease and three have diabetes mellitus (DM), not usually seen in the LD syndrome. Polymorphisms of FOXC2 in diabetics have been studied in different populations. Our sequence analysis of the 5' untranslated region (UTR) C-512T shows the homozygous T allele in all family members tested. The sequencing data in this family suggests the possibility of a novel phenotype-haplotype. This novel phenotype, LD/renal disease/type 2 diabetes, might be the result of a combination of the nt 1006--1007 insA and the upstream UTR homozygous T polymorphism.

Research perspectives in inherited lymphatic disease

The hereditary lymphedemas provide an opportunity to identify genes involved in normal and deranged lymphatic development. Genetic analysis of families with Milroy's disease identified mutations in VEGFR3 as a cause of congenital lymphedema, confirming the importance of VEGFC/VEGFR3 signaling in lymphatic development. These observations led to the identification of a mouse model for primary lymphedema, and subsequent analysis of this mouse model, using transgenic and gene transfer techniques, has provided initial clues to the development of a biologically based therapy for primary lymphedema. Of more importance from a public health perspective is the fact that manipulation of this pathway may lead to effective therapies for the more prevalent forms of secondary lymphedema. Identification of FOXC2 as the gene mutated in the lymphedema-distichiasis syndrome has revealed new molecular insight into lymphatic development. Molecular analysis of the FOXC2 pathway may provide clues to developmental pathways shared by the lymphatic system and the other developmental abnormalities associated with this complex syndrome. With improving knowledge of the human genome, genetic analysis of families with lymphedema continues to offer one of the most promising approaches to identifying genes influencing lymphatic development.

Lymphedema-distichiasis syndrome and FOXC2 gene mutation

PURPOSE

To describe the clinical characteristics of a family with autosomal dominant lymphedema-distichiasis syndrome and to report the results of analysis of the FOXC2 gene

DESIGN

Observational and experimental study.

METHODS

The setting was a clinical practice. The study population was 17 members of a family with lymphedema-distichiasis. Observation procedures were complete ophthalmologic examinations and collection of blood samples. DNA was extracted. Mutation analysis of the coding region of the FOXC2 gene was performed using direct sequencing of polymerase chain reaction (PCR) product and a restriction enzyme assay. The main outcome measure was inheritance of mutation in FOXC2 gene.

RESULTS

Nine patients had distichiasis or lymphedema or both and eight did not. Sequencing of the coding region of the only translated exon of the FOXC2 gene revealed a C to A transversion at position 939 resulting in a Tyr313Stop codon with premature termination of translation and a truncated protein product. The mutation was present in all nine affected individuals and in an asymptomatic 9-year-old boy.

CONCLUSIONS

Distichiasis-lymphedema syndrome results from mutations in FOXC2, a member of the forkhead/winged family of transcription factors. There is intrafamilial variation in the clinical expression of the mutation.

Analysis of the phenotypic abnormalities in lymphoedema-distichiasis syndrome in 74 patients with FOXC2 mutations or linkage to 16q24

INTRODUCTION

Lymphoedema-distichiasis syndrome (LD) (OMIM 153400) is a rare, primary lymphoedema of pubertal onset, associated with distichiasis. Causative mutations have now been described in FOXC2, a forkhead transcription factor gene. Numerous clinical associations have been reported with this condition, including congenital heart disease, ptosis, varicose veins, cleft palate, and spinal extradural cysts.

SUBJECTS

We report clinical findings in 74 affected subjects from 18 families and six isolated cases. All of them were shown to have mutations in FOXC2 with the exception of one family who had two affected subjects with lymphoedema and distichiasis and linkage consistent with the 16q24 locus.

RESULTS

The presence of lymphoedema was highly penetrant. Males had an earlier onset of lymphoedema and a significantly increased risk of complications. Lymphatic imaging confirmed the earlier suggestion that LD is associated with a normal or increased number of lymphatic vessels rather than the hypoplasia or aplasia seen in other forms of primary lymphoedema. Distichiasis was 94.2% penetrant, but not always symptomatic. Associated findings included ptosis (31%), congenital heart disease (6.8%), and cleft palate (4%). Other than distichiasis, the most commonly occurring anomaly was varicose veins of early onset (49%). This has not been previously reported and suggests a possible developmental role for FOXC2 in both venous and lymphatic systems. This is the first gene that has been implicated in the aetiology of varicose veins.

CONCLUSION

Unlike previous publications, the thorough clinical characterisation of our patients permits more accurate prediction of various phenotypic abnormalities likely to manifest in subjects with FOXC2 mutations.

Lymphangiogenesis and lymphangiodysplasia: from molecular to clinical lymphology

The lymph vascular system parallels the blood vasculature and as one of its key functions returns liquid and solutes to the bloodstream, including macromolecules that have escaped from blood capillaries and entered the interstitium. In conjunction with interspersed lymph nodes and lymphoid organs, the lymphatic vasculature also acts as a conduit for trafficking immune cell populations. Echoing the explosion of knowledge about blood vessel angiogenesis (properly termed "hemangiogenesis"), the past two decades have also witnessed a series of significant, yet less-noticed discoveries bearing on "lymphangiogenesis," along with delineation of the spectrum of lymphedema-angiodysplasia syndromes. Failure of lymph transport promotes a brawny proteinaceous edema of the affected limb, organ, or serous space that is disfiguring, disabling, and on occasion even life-threatening. Key members of the vascular endothelial growth factor (VEGF) and angiopoietin families of vascular growth factors (and their corresponding tyrosine kinase endothelial receptors) have been identified which preferentially influence lymphatic growth and, when manipulated in genetically engineered murine models, produce aberrant "lymphatic phenotypes." Moreover, mutations in VEGF receptor and forkhead family developmental genes have now been linked and implicated in the pathogenesis of two familial lymphedema-angiodysplasia syndromes. Thus, recent advances in "molecular lymphology" are elucidating the poorly understood development, physiology, and pathophysiology of the neglected lymphatic vasculature. In combination with fresh insights and refined tools in "clinical lymphology," these advances should lead not only to earlier detection and more rational classification of lymphatic disease but also to better therapeutic approaches, including designer drugs for lymphangiostimulation and lymphangioinhibition and gene therapy to modulate lymphatic growth.

Mutations in FOXC2 (MFH-1), a forkhead family transcription factor, are responsible for the hereditary lymphedema-distichiasis syndrome

Lymphedema-distichiasis (LD) is an autosomal dominant disorder that classically presents as lymphedema of the limbs, with variable age at onset, and double rows of eyelashes (distichiasis). Other complications may include cardiac defects, cleft palate, extradural cysts, and photophobia, suggesting a defect in a gene with pleiotrophic effects acting during development. We previously reported neonatal lymphedema, similar to that in Turner syndrome, associated with a t(Y;16)(q12;q24.3) translocation. A candidate gene was not found on the Y chromosome, and we directed our efforts toward the chromosome 16 breakpoint. Subsequently, a gene for LD was mapped, by linkage studies, to a 16-cM region at 16q24.3. By FISH, we determined that the translocation breakpoint was within this critical region and further narrowed the breakpoint to a 20-kb interval. Because the translocation did not appear to interrupt a gene, we considered candidate genes in the immediate region that might be inactivated by position effect. In two additional unrelated families with LD, we identified inactivating mutations-a nonsense mutation and a frameshift mutation-in the FOXC2 (MFH-1) gene. FOXC2 is a member of the forkhead/winged-helix family of transcription factors, whose members are involved in diverse developmental pathways. FOXC2 knockout mice display cardiovascular, craniofacial, and vertebral abnormalities similar to those seen in LD syndrome. Our findings show that FOXC2 haploinsufficiency results in LD. FOXC2 represents the second known gene to result in hereditary lymphedema, and LD is only the second hereditary disorder known to be caused by a mutation in a forkhead-family gene.

Distichiasis-lymphoedema: clinical features, venous function and lymphoscintigraphy

Distichiasis-lymphoedema is a rare variant of the genetically determined lymphoedemas; distichiasis is the abnormal development of the meibomian glands causing aberrant growth of eyelashes. However, a better understanding of this clinically distinct subgroup may provide useful information on the genetic inheritance of all types of lymphoedema. This report provides phenotype data on a very large family with distichiasis-lymphoedema. Lymphoscintigraphy and light reflection rheography (venous function) were undertaken to identify the phenotype more clearly. As a result of lymphoscintigraphy several subjects were reclassified phenotypically (unaffected or affected) with implications for genetic linkage studies. Associated congenital abnormalities were found and venous abnormalities were almost always present in affected limbs. A dominant inheritance with incomplete penetrance was confirmed.

Distichiasis-lymphedema syndrome: tetralogy of Fallot, chylothorax, and neonatal death

We describe a newborn female with a severe presentation of distichiasis-lymphedema syndrome (McKusick 15340). She was initially evaluated because of a phenotype suggestive of Ullrich-Turner or Noonan syndrome (low posterior hairline, cupped ears, severe pterygium colli, heart murmur, and pectus excavatum). Distichiasis was noted at age 6 weeks. Subsequent to surgery for tetralogy of Fallot, patent ductus arteriosus, and branch pulmonic stenosis, she developed persistent chylothorax and sepsis. She died at 3 months. Family history indicated segregation of distichiasis-lymphedema syndrome. She was the sixth member in her family to have this disorder and was the most severely affected.

Hereditary lymphedema and distichiasis

Two patients with lymphedema-distichiasis syndrome illustrate that both Milroy's disease and late-onset hereditary lymphedema are sometimes associated with distichiasis. It is important for ophthalmologists to be aware of the lymphedema-distichiasis syndrome because of its ophthalmic manifestations and the associated systemic abnormalities that can be potentially life threatening.