King syndrome: further clinical variability and review of the literature

Neuropsychology and socioeconomic aspects of Klinefelter syndrome: new developments

PURPOSE OF REVIEW

To summarize recent important studies on neuropsychology and epidemiology of Klinefelter syndrome. PubMed was searched for 'Klinefelter', 'Klinefelter's' and 'XXY' in titles and abstracts. Relevant studies were obtained and reviewed, as well as other articles selected by the authors.

RECENT FINDINGS

Klinefelter syndrome is the most common sex-chromosome disorder in humans, affecting one in 660 men. The key findings in Klinefelter syndrome are small testes, hypergonadotropic hypogonadism and cognitive impairment. Klinefelter syndrome scores significantly below education matched controls on a range of cognitive tests with verbal skills displaying the largest effects. Boys with Klinefelter syndrome are often in the need of speech therapy and many suffer from learning disability and may benefit from special education. New studies are elucidating aspects of cognitive functioning and suggesting that neuropsychological treatment may be of value. The socioeconomic status and educational level of Klinefelter syndrome is severely affected with many struggling to achieve any or only shorter education, resulting in low-income levels and early retirement. In addition, few become fathers and fewer live with a partner compared with controls. Medical treatment is mainly testosterone replacement therapy in order to alleviate acute and long-term consequences of hypogonadism, as well as, treating or preventing the frequent comorbidity.

SUMMARY

The neurocognitive phenotype of Klinefelter syndrome is being unraveled and the need for psychological and cognitive treatment in many cases is evident. The neurocognitive deficits no doubt influence the socioeconomic status of many Klinefelter syndrome patients, which is clearly inferior to age-matched controls.

Development and maturation of the spinal cord: implications of molecular and genetic defects

The human central nervous system (CNS) may be the most complex structure in the universe. Its development and appropriate specification into phenotypically and spatially distinct neural subpopulations involves a precisely orchestrated response, with thousands of transcriptional regulators combining with epigenetic controls and specific temporal cues in perfect synchrony. Understandably, our insight into the sophisticated molecular mechanisms which underlie spinal cord development are as yet limited. Even less is known about abnormalities of this process - putative genetic and molecular causes of well-described defects have only begun to emerge in recent years. Nonetheless, modern scientific techniques are beginning to demonstrate common patterns and principles amid the tremendous complexity of spinal cord development and maldevelopment. These advances are important, given that developmental anomalies of the spinal cord are an important cause of mortality and morbidity (Sadler, 2000); it is hoped that research advances will lead to better methods to detect, treat, and prevent these lesions.

Neonatal-onset nemaline myopathy mimicking congenital diaphragmatic hernia

In a newborn with severe respiratory failure and abnormal elevation of the right diaphragm, congenital diaphragmatic hernia with sac was diagnosed during surgery. However, microscopic examination of the sac showed atrophic striated muscle cells, indicating eventration instead of hernia. After several extubation failures, the final diagnosis of nemaline myopathy was made by skeletal muscle biopsy. In diaphragmatic defects with sac, diaphragm microscopic analysis should be recommended in order to discriminate between hernia and eventration. Congenital myopathies may underlie such diaphragmatic defects and should be promptly recognized, given their prognostic implications.

Anesthetic management of a ventilator-dependent parturient with the King-Denborough syndrome

PURPOSE

The King-Denborough syndrome (KDS) is a rare disorder that is associated with myopathy, susceptibility to malignant hyperthermia (MH) as well as congenital skeletal and facial anomalies. We report the anesthetic management of a parturient with KDS.

CLINICAL FEATURES

We describe the management of a 24-yr-old primiparous woman with a diagnosis of KDS and a history of previous MH reaction (age two). Her KDS resulted in chronic respiratory failure. She had a permanent tracheostomy and required overnight ventilatory support for the previous two years. She had three admissions during her pregnancy, one for pneumonia and two for preterm labour. Labour was induced at 37 weeks. Her labour was managed in the operating room where a "clean" anesthesia machine was ready. Cooling aids and a MH emergency kit were immediately available. Intravenous access, an arterial line and a lumbar epidural catheter were inserted before induction of labour. Ropivacaine 0.08% + fentanyl 2 microg x mL(-1) were used for patient-controlled epidural analgesia. After 6.5 hr of labour the patient required ventilation. An outlet forceps was performed for delivery. Postpartum, she was ventilated overnight in the intensive care unit.

CONCLUSION

The use of epidural analgesia, close monitoring and collaboration between the various disciplines were important in achieving a safe and uneventful labour in this high-risk parturient.

PTPN11 mutations in Noonan syndrome type I: detection of recurrent mutations in exons 3 and 13

We surveyed 16 subjects with the clinical diagnosis of Noonan Syndrome (NS1) from 12 families and their relevant family members for mutations in PTPN11/SHP2 using direct DNA sequencing. We found three different mutations among five families. Two unrelated subjects shared the same de novo missense substitution in exon 13 (S502T); an additional two unrelated families had a mutation in exon 3 (Y63C); and one subject had the amino acid substitution Y62D, also in exon 3. None of the three mutations were present in ethnically matched controls. In the mature protein model, the exon 3 mutants and the exon 13 mutant amino acids cluster at the interface between the N' SH2 domain and the phosphatase catalytic domain. Six of eight subjects with PTPN11/SHP2 mutations had pulmonary valve stenosis while no mutations were identified in those subjects (N = 4) with hypertrophic cardiomyopathy. An additional four subjects with possible Noonan syndrome were evaluated, but no mutations in PTPN11/SHP2 were identified. These results confirm that mutations in PTPN11/SHP2 underlie a common form of Noonan syndrome, and that the disease exhibits both allelic and locus heterogeneity. The observation of recurrent mutations supports the hypothesis that a special class of gain-of-function mutations in SHP2 give rise to Noonan syndrome.

King-Denborough Syndrome: report of two Brazilian cases

We report on two boys aged 2 and 6 years-old respectively with dysmorphic face, ptosis, down-slanting palpebral fissures, hypertelorism, epicanthic folds, low-set ears, malar hypoplasia, micrognathia, high-arched palate, clinodactyly, palmar simian line, pectus excavatum, winging of the scapulae, lumbar lordosis and mild thoracic scoliosis who present congenital hypotonia, slightly delayed motor development, diffuse joint hyperextensibility and mild proximal weakness. The muscle biopsy revealed minimal but identifiable changes represented by size fiber variability, type I fiber predominance and atrophy, perimysial fibrous infiltration and some disarray of the intermyofibrillary network. These cases correspond to the first Brazilian reports of the King-Denborough syndrome and our objective is increasing the awareness of this disorder as these patients are predisposed to developing malignant hyperthermia.

Rhabdomyolysis: a review

Rhabdomyolysis, a syndrome of skeletal muscle breakdown with leakage of muscle contents, is frequently accompanied by myoglobinuria, and if sufficiently severe, acute renal failure with potentially life-threatening metabolic derangements may ensue. A diverse spectrum of inherited and acquired disorders affecting muscle membranes, membrane ion channels, and muscle energy supply causes rhabdomyolysis. Common final pathophysiological mechanisms among these causes of rhabdomyolysis include an uncontrolled rise in free intracellular calcium and activation of calcium-dependent proteases, which lead to destruction of myofibrils and lysosomal digestion of muscle fiber contents. Recent advances in molecular genetics and muscle enzyme histochemistry may enable a specific metabolic diagnosis in many patients with idiopathic recurrent rhabdomyolysis.

Genetics and pathogenesis of malignant hyperthermia

Malignant hyperthermia (MH) is a potentially life-threatening event in response to anesthetic triggering agents, with symptoms of sustained uncontrolled skeletal muscle calcium homeostasis resulting in organ and systemic failure. Susceptibility to MH, an autosomal dominant trait, may be associated with congenital myopathies, but in the majority of the cases, no clinical signs of disease are visible outside of anesthesia. For diagnosis, a functional test on skeletal muscle biopsy, the in vitro contracture test (IVCT), is performed. Over 50% of the families show linkage of the IVCT phenotype to the gene encoding the skeletal muscle ryanodine receptor and over 20 mutations therein have been described. At least five other loci have been defined implicating greater genetic heterogeneity than previously assumed, but so far only one further gene encoding the main subunit of the voltage-gated dihydropyridine receptor has a confirmed role in MH. As a result of extensive research on the mechanisms of excitation-contraction coupling and recent functional characterization of several disease-causing mutations in heterologous expression systems, much is known today about the molecular etiology of MH.