Are ECG abnormalities in Noonan syndrome characteristic for the syndrome?

Of all patients with Noonan syndrome, 50-90% have one or more congenital heart defects. The most frequent occurring are pulmonary stenosis (PS) and hypertrophic cardiomyopathy. The electrocardiogram (ECG) of a patient with Noonan syndrome often shows a characteristic pattern, with a left axis deviation, abnormal R/S ratio over the left precordium, and an abnormal Q wave. The objective of this study was to determine if these ECG characteristics are an independent feature of the Noonan syndrome or if they are related to the congenital heart defect. A cohort study was performed with 118 patients from two university hospitals in the United States and in The Netherlands. All patients were diagnosed with definite Noonan syndrome and had had an ECG and echocardiography. Sixty-nine patients (58%) had characteristic abnormalities of the ECG. In the patient group without a cardiac defect (n = 21), ten patients had a characteristic ECG abnormality. There was no statistical relationship between the presence of a characteristic ECG abnormality and the presence of a cardiac defect (p = 0.33). Patients with hypertrophic cardiomyopathy had more ECG abnormalities in total (p = 0.05), without correlation with a specific ECG abnormality. We conclude that the ECG features in patients with Noonan syndrome are characteristic for the syndrome and are not related to a specific cardiac defect. An ECG is very useful in the diagnosis of Noonan syndrome; every child with a Noonan phenotype should have an ECG and echocardiogram for evaluation.

[The Noonan syndrome from a pediatric perspective]. / Het Noonan-syndroom vanuit kindergeneeskundig perspectief.

Noonan syndrome is a relatively common autosomal dominant condition characterised by cardiac defects, short stature, feeding difficulties during the first year of life, and learning and behavioural problems later in life. The diagnosis is clinical and in 50% of cases it can be confirmed by a mutation in the PTPN11 gene. Studies into the effect of growth hormone treatment on final height have yet to provide any definite conclusions. Therefore, for the time being this treatment should be carried out in a research setting. Early-childhood feeding difficulties are troublesome. However, these disappear spontaneously and do not seem to negatively affect growth. Specific developmental patterns, resulting in behavioural and learning problems (non-verbal learning disability) are frequently encountered and require a specific approach.

A female patient with neurological, facial, digital and renal abnormalities: another case of the neurofaciodigitorenal (NFDR) syndrome?

We report a female patient with severe mental retardation and multiple congenital anomalies. These consist of unusual facies (grooved, nasal tip, ptosis, malformed auricles), abnormal digits, and congenital heart and renal defects. These findings strongly resemble the NFDR syndrome, first described by Freire-Maia et al.

T cell subsets and T cell function in cartilage-hair hypoplasia.

Cartilage hair hypoplasia is a rare autosomal recessive form of short-limbed dwarfism associated with a cellular immunodeficiency. In eight patients, the authors studied the presence of T cell subsets and in vitro T cell function in order to address the basis for the immunological disorder. Both the proliferative response to phytohaemagglutinin (PHA) and the PHA-induced IL2 production were 60% lower compared with controls (P = 0.007 and 0.005, respectively). The impaired proliferative response could not be restored by addition of IL-2. This result is in accordance with a decrease in the percentage of activated T cells expressing the p55 subunit of the IL-2 receptor complex (CD25). The results define more precisely that T cells from cartilage hair hypoplasia patients are defective in the transition from the G0 to the G1 phase of the cell cycle. Furthermore, the data demonstrate that several CHH patients show a reduced proportion of CD45RA+ 'naive' T cells. However, the in vitro impairment of T cell function cannot solely be explained by imbalance between 'naive' and 'memory' T cells. Although CHH patients with a history of recurrent respiratory tract infections showed the most aberrant in vitro immune parameters, a clear relationship between clinical data and in vitro parameters could not be established for the whole patient group.

Myopathology in patients with a Noonan phenotype.

Two patients with a Noonan phenotype and progressive hypertrophic obstructive cardiomyopathy are described, in whom abnormal histopathological changes in striated musculature were detected. In both patients an increased density of muscle spindles was found at biopsy. The significance of an increased density of muscle spindles in patients with Noonan phenotype can only be speculated. The question is raised of whether these changes are a distinct feature within the spectrum of patients with Noonan phenotype.

Ectrodactyly of lower limbs, congenital heart defect and characteristic facies in four unrelated Dutch patients: a new association.

We report four cases with the unusual combination of lower limb ectrodactyly, congenital heart defect and a characteristic (albeit non-specific) facies. Because of the striking similarities between these cases we propose that they constitute a new association.

Nijmegen Breakage syndrome: a progress report.

We report the findings in the first 30 patients with the Nijmegen Breakage Syndrome (NBS). All had microcephaly from birth, short stature and a 'bird-like' face. Most of them suffered from recurrent respiratory tract infections. Intelligence was normal in half of the patients. Serum immunoglobulins were disturbed in 22/25 patients investigated (IgG deficiency, IgA deficiency, IgG2 and IgG4 deficiency) and T cell defects were found in 23/24 patients tested. The immunodeficiency appears to be more severe than in A-T. Chromosomal aberrations in cultured T lymphocytes occurred preferentially in chromosomes 7 and 14 and at the same breakpoints as in A-T. However, the percentage of chromosome 7 and/or 14 rearrangements was significantly higher in NBS patients than in A-T patients (p < 0.0005). Inv(7) was amongst the most frequently detected aberration in NBS cells as it is in A-T cells. Large clones of cells with rearrangements of chromosome 14 were rare in NBS. Of the first 19 reported patients eight have already developed a malignancy: seven a lymphoma and one a meningioma. It is noteworthy that both the tendency to express rearrangements of chromosomes 7 and 14 and the tendency to develop a malignancy is much higher in NBS than in A-T. Whether there is any causal relationship is as yet unknown.

Familial Angelman syndrome with a crossover in the critical deletion region.

More than two thirds of the patients with Angelman syndrome (AS) carry a deletion or other chromosomal abnormality in the 15q11-13 region. A much less frequent cause (4%) is paternal uniparental disomy of the entire chromosome. In general no abnormalities are detectable in familial cases and an inherited submicroscopic deletion was described only once. Here a familial case of 2 sibs with AS is reported. No major cytogenetic or molecular abnormality was identified, but a recombination event had occurred in the AS critical region. The AS locus, D15S113, D15S10, D15S11, and D15S18 mapped proximal and the GABRB3 gene, D15S97, the GABRA5 gene, and D15S12 distal to the crossover site. This recombination within the AS critical region confirmed the exclusion of GABRB3 as a candidate gene for AS. Other markers and candidate genes can be tested genetically as well for a possible role in AS.

Antibody deficiency and isolated growth hormone deficiency in a girl with Mulibrey nanism.

A combination of humoral immunodeficiency and isolated growth hormone deficiency was observed in a girl with Mulibrey nanism. The humoral immunodeficiency consisted of subnormal concentration of serum IgG, in particular IgG2 and IgG4, and low concentration of serum IgM. Serum IgA and IgD were elevated, IgE was absent. Antibody response in vivo was very low or absent and opsonization in vitro was defective. Total B-cell number was low. In addition, the serum kappa/lambda light chain ratios within the immunoglobulin classes G, A, and M were abnormal. The defective antibody response may be linked to the abnormal kappa/lambda light chain ratios. Endocrine functions were normal except for isolated growth hormone deficiency. Therapy with human growth hormone resulted in increased growth velocity but did not improve humoral immune functions.

Partial trisomy for 5q and monosomy for 12p in a liveborn child as a result of a complex five breakpoint chromosome rearrangement in a parent.

A balanced complex chromosome rearrangement (CCR) involving four chromosomes is very rare and may lead to different types of aneuploid germ cells. We report a liveborn child with multiple congenital anomalies and an apparently balanced translocation, t(11;12). High resolution chromosome analysis in the mother showed a CCR involving chromosomes 5, 11, 12, and 16. In situ hybridisation showed that this CCR was the result of a five break rearrangement, and that the derivative chromosome 12 consisted of parts of chromosomes 5, 11, and 12. From this it could be deduced that the karyotype of the child was not balanced, but resulted in partial trisomy for 5q and partial monosomy for 12p. The clinical findings in the child were compatible with partial trisomy for 5q.

Hearing loss in Noonan syndrome.

A report is presented on a man of Turkish origin, with Noonan Syndrome and unilateral conductive hearing loss since early childhood. There was no history of otitis media. At the age of 23, exploratory tympanotomy revealed a total absence of the long process of the incus and a normal-looking tympanic membrane. The position of the normal-shaped mobile stapes was just medial, and not posteromedial, to the malleus. A congenital ossicular chain anomaly was diagnosed. An allograft malleus head was interposed between the stapes and the malleus. The resulting air-bone gap was less than 10 dB. A review of the literature is given on hearing loss in Noonan Syndrome.