Tetraphocomelia in the syndrome of thrombocytopenia with absent radii (TAR syndrome)

Congenital Synostosis of the Knee: Long-term Outcomes of Limb Reconstruction Surgery

BACKGROUND

Congenital synostosis of the knee is a rare condition with limited data on treatment options and outcomes. This study reports clinical findings, treatment approach, and surgical/clinical outcomes for congenital synostosis of the knee.

METHODS

An institutional review board-approved retrospective review of patients with congenital synostosis of the knee presenting to 2 institutions between 1997 and 2021 was performed.

RESULTS

Eight patients (13 knees) with a median follow-up of 11.3 years (3.3 to 17 y) were included. Seven patients had associated syndromes. Patients presented with an average knee flexion deformity of 100° (range 60 to 130°) and delayed walking ability. Seven patients had associated upper extremity hypoplasia/phocomelia. The average age at the index surgery was 4.3 years (range 1.2 to 9.2 y). Synostosis resection with gradual deformity correction was performed in most patients. An attempt was made at a mobile knee in some patients, but all went on to knee fusion. Mean flexion deformity at final follow-up was 11.6° (range: 0 to 40°) and 5 limbs were fused in full extension. Mean limb length discrepancy at final follow-up was 6.8 cm (range: 0 to 8 cm). All patients maintained their improved ambulation status at final follow-up. Twenty-two complications were identified.

CONCLUSIONS

Reliable correction of the deformity associated with congenital knee synostosis was achieved at a median follow-up of 11 years. Importantly, all patients maintained their improved ambulation at final follow-up. This is the largest study on patients with congenital knee synostosis and outlines a reconstructive approach to improve ambulatory status.

LEVEL OF EVIDENCE

Level IV.

Reconstruction of limb deformities in patients with thrombocytopenia-absent radius syndrome

OBJECTIVE

Developmental abnormalities of the appendicular skeleton are among the most common and easily identified birth defects. The aim of this report was to describe the phenotypic characterization of several patients with thrombocytopenia-absent radius (TAR) syndrome and the orthopaedic interventions performed on them. TAR syndrome is inherited in an autosomal recessive manner and results from compound heterozygosity of RBM8A mutations.

METHODS

Reconstructions were designed and performed in five patients with TAR syndrome, mainly comprising orthopaedic interventions to correct their upper limb defects. Additional lower limb deformities (severe internal rotation of the tibiae) was been encountered in one patient.

RESULTS

The affected patients' wrists were re-aligned and stabilized and the musculotendinous forces around the wrist rebalanced to reverse the ulnar forearm bow.

CONCLUSION

Patients with TAR syndrome who receive optimal treatment can expect to return to most activities of daily living with some limitation of wrist extension and ulnar deviation and, of course, with a reduced total active range of digital motion.

Vascular malformations. Part II: associated syndromes

Cutaneous vascular malformations are rare disorders representing errors in vascular development. These lesions occur much less commonly but are often confused with the common infantile hemangioma. It is important to properly diagnose vascular malformations because of their distinct differences in morbidity, prognosis and treatment. Vascular malformations may be associated with underlying disease or systemic anomalies. Several of these syndromes are well defined and can often be distinguished on the basis of the flow characteristics of the associated vascular malformation.

LEARNING OBJECTIVE

At the completion of this learning activity, participants should be able to better recognize underlying diseases or systemic anomalies that may be associated with vascular malformations. Participants should also better understand the various syndromes and conditions discussed and become more familiar with their management.

Thrombocytopenia-absent radius syndrome: a clinical genetic study

The thrombocytopenia-absent radius (TAR) syndrome is a congenital malformation syndrome characterised by bilateral absence of the radii and a thrombocytopenia. The lower limbs, gastrointestinal, cardiovascular, and other systems may also be involved. Shaw and Oliver in 1959 were the first to describe this condition, but it was Hall et al in 1969 who reported the first major series of patients. Since then most reports have been based on single or small numbers of cases. We report the results of a clinical study looking at the phenotype of 34 patients with TAR syndrome. All cases had a documented thrombocytopenia and bilateral radial aplasia, 47% had lower limb anomalies, 47% cow's milk intolerance, 23% renal anomalies, and 15% cardiac anomalies. Congenital anomalies not previously described in association with TAR syndrome included facial capillary haemangiomata, intracranial vascular malformation, sensorineural hearing loss, and scoliosis. Karyotype analysis, chromosome breakage studies including premature centromeric separation and fluorescence in situ hybridisation studies looking for a deletion of chromosome 22q11 were undertaken. Two abnormal karyotypes were identified.

Bilaterally cleft lip, limb defects, and haematological manifestations: Roberts syndrome versus TAR syndrome

We report on a 13-year-old patient followed since birth. He is the only offspring of young, non-consanguineous German parents. His mother has an isolated left cleft of lip and a cleft palate. At birth, our patient presented with bilaterally cleft lip/cleft palate, phocomelia of upper limbs with normal hands, and mild symmetrical deficiencies of the long bones of the lower limbs. Haematological evaluation demonstrated a leukaemoid reaction during a urinary tract infection as well as intermittent thrombocytopenia and episodes of marked eosinophilia during the first two years of life. Intellectual development has been normal. Comparison with two similar cases from the literature suggests a non-random phenotypic overlap of Roberts syndrome (MIM 268300) and TAR syndrome (MIM 274000). Such clinical constellations may be key observations to understand the genetic relationship of Roberts syndrome and TAR syndrome in future phenotype-genotype correlations.

Bilateral radial deficiency with lower limb involvement

We describe a 10-month-old boy with an unclassified form of radial aplasia with absent thumbs, tibia hypo/-aplasia, and partial absence of toes. Only a few cases with similar limb deficiencies have been published. We try to classify the malformations on the basis of embryological considerations and discuss possible differential diagnosis.

Severe case of Al Awadi/Raas-Rothschild syndrome or new, possibly autosomal recessive facio-skeleto-genital syndrome

A Sicilian girl whose parents were first cousins had a severe tetramelic limb deficiency (amelia of lower limbs, peromelia of upper limbs) and other defects including cleft lip and palate, facial anomalies, athelia, low umbilicus, bladder exstrophy, no external genitalia, and anteriorly displaced anus. This probably represents a particularly severe case of Al Awadi/Raas-Rothschild syndrome (limb/pelvis-hypoplasia/aplasia syndrome, LPHAS), but the possibility of a new autosomal recessive facio-skeleto-genital syndrome cannot be excluded.

von Voss-Cherstvoy syndrome: a variable perinatally lethal syndrome of multiple congenital anomalies

We report 4 cases and review 7 from the literature with a pattern suggesting a variable early lethal multiple congenital anomaly syndrome. This was first reported by von Voss et al. [1979: "Klinische Genetik in der Pädiatrie," pp 70-74] and Cherstvoy et al. [1980: Lancet ii:485], and can affect upper limbs, face, brain, heart, lungs, urogenital and gastrointestinal systems, vertebrae and ribs, and can include thrombocytopenia. The initial cases had occipital encephaloceles and phocomelia, but milder cerebellar anomalies and radial ray defects may be seen instead. Both sexes are affected and parental age is not increased. This may be heterogeneous, but two consanguineous families, one with recurrences, suggest autosomal recessive inheritance in at least some instances, although the recurrences had milder brain findings than the other cases. The original designation of DK-phocomelia syndrome is inaccurate, since arm findings may be limited to radial anomalies; we suggest instead the von Voss-Cherstvoy syndrome. This may be heterogeneous, but at present, phenotypic overlap prevents differentiation of subgroups. The disorder appears to be part of a group of syndromes with radial and hematologic abnormalities.

TAR-like syndrome in a consanguineous Mayan girl

We report on a 3-month-old girl with a TAR-like syndrome. Her older brother died with a similar disorder at 3 months of unknown causes. The parents are second cousins of Mayan ancestry. The infant also had, in addition to the usual abnormalities of TAR syndrome, depressed nasal bridge, cataracts, glaucoma, megalocorneae, and blue sclerae.

Explaining certain human limb anomalies and the limb-hematopoiesis community of syndromes using a model of determination

Disturbances of determination, the process of limitation of developmental potential, can cause structural as well as histologic anomalies. A polar coordinate model (PCM) developed from studies in animals, in which determination depends upon positional information arranged along polar coordinates, can be used to explain certain classes of human limb anomalies. Under the model, interference with this system primarily affects distal patterning. If the radial area is distal to the zone of polarizing activity in embryological development, as it appears to be, the PCM explains the teratologic equivalence of preaxial duplications and deficiencies in certain circumstances and the prevalence of ulnar dimelias in forearm duplications. Also, failures of hematopoiesis can be considered late problems with determination and may be markers for abnormalities of a determinative process that also has earlier developmental consequences. Abnormalities of retinoic acid morphogen receptors would be one possible mechanism. This would provide a rationale for the known association of postnatal hematologic problems with developmental anomalies preferentially affecting the radial area. Syndromes with limb and hematopoietic problems may well be a community of determinative disorders.

Prenatal diagnosis of thrombocytopenia absent radius syndrome by ultrasound and cordocentesis

The prenatal diagnosis of thrombocytopenia absent radius (TAR) syndrome, utilizing ultrasound and cordocentesis, is described. To our knowledge, this represents the first prenatal diagnosis of this condition in an index case. The diagnostic evaluation of a fetus with upper extremity limb reduction defects is discussed.

Intermittent thrombocytopenia and absent radii: report of a patient with additional unusual manifestations

We report on a boy with absent radii and intermittent thrombocytopenia. He has many other manifestations of the thrombocytopenia absent radius (TAR) syndrome but in addition has manifestations not previously described: palatoschisis of the soft palate, subcricoid stenosis, duodenal atresia and extreme sensitivity of chromosomes to X-rays. Our patient could either represent a unique condition or unusual variability of TAR syndrome.

Clinical manifestations of the thrombocytopenia and absent radii (TAR) syndrome

Six patients with the classical features of the TAR syndrome were diagnosed at birth. In one case an older sibling was also affected. The characteristic features of foreshortened forearms and radially deviated hands were noted in all cases at presentation and confirmed radiologically. With one exception skeletal abnormalities of the lower limbs were also present. Varying degrees of thrombocytopenia were present at birth with three of the five patients having platelet counts below 50 x 10(9)/L. Bone marrow examination was performed in two patients and revealed an absence of normal megakaryocytes. Two patients with severe thrombocytopenia had bleeding complications during infancy requiring transfusion support. Severe gastroenteritis occurred in two patients, in one of whom it was attributed to cow's milk intolerance. In all patients the platelet count has risen progressively since birth. Orthopedic surgical procedures have been performed without hemorrhagic complications.

Pathological features and prenatal diagnosis in the newly recognised limb/pelvis-hypoplasia/aplasia syndrome

A second family with the autosomal recessive disorder now referred to as the limb/pelvis-hypoplasia/aplasia syndrome is reported. It is speculated that the gene for this rare skeletal dysplasia may be confined to the Middle East gene pool. The disorder has been shown to be diagnosable prenatally in a pregnancy at risk by using ultrasonography.

Thrombocytopenia with absent radius in a boy and his uncle

We report a boy and his maternal uncle who have Thrombocytopenia-Absent Radius (TAR) syndrome. The mother of the propositus is normal. A maternal aunt has mild radial hypoplasia, possibly representing partial expression of the syndrome. A review of the literature shows several pedigrees in which relatives other than sibs were affected with TAR. Thus, autosomal recessive inheritance may not account for all cases and alternate modes of transmission should be considered.

Thrombocytopenia and absent radius (TAR) syndrome

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