KBG Syndrome

At a glance

Polymalformative syndrome characterized by short stature (dwarfism), mental retardation, dental abnormalities, craniofacial dysmorphism, and skeletal (vertebral and limbs) anomalies.

Synonyms

Herrmann-Pallister Syndrome; Herrmann-Pallister-Opitz Syndrome; Short Stature, Facial/Skeletal Anomalies-Retardation-Macrodontia Syndrome.

History

First described in 1975 by J. Herrmann, P. D. Pallister, W. Tiddy, and J. M. Opitz in two families with multiple affected members. The designation “KBG-Syndrome” reflects Opitz’s preference of using the initials of patients’ last names to define medical conditions.

Incidence

To date, about 150 cases have been reported in the literature.

Genetic inheritance

Autosomal dominant, but sporadic with mutations. It has also been associated with mutations in the ANKRD11 gene or microdeletion on chromosome 16q that involves the ANKRD11 gene. Mutations occur spontaneously without family history.

Clinical aspects

These patients have short stature (often below the third percentile; particularly short trunk, which may in part be due to anterior wedging and abnormal upper and lower plates of the vertebrae) and typical facial features that may include brachycephaly, hypertelorism, wide and bushy eyebrows, large prominent ears, anteverted nostrils with small alae nasi, long philtrum, and oligo- and/or macrodontia. Cryptorchidism seems to be quite common in male patients. Other features that have been described in some of the patients include low anterior and posterior hairline, fused or wide upper central incisors, short metacarpalia and clinodactyly, accessory cervical ribs, thoracic kyphosis, and cardiac defects (eg, ventricular septal defect). Mental retardation, however, is a constant finding and may be severe and accompanied by seizures. Hypoplasia of the cerebellar vermis or the posterior fossa could be demonstrated in some patients.

Precautions before anesthesia

The association between this medical condition and cardiac anomalies necessitate proper cardiological evaluation before elective surgical procedures. The presence of cardiomegaly, left-to-right shunt, and congestive pulmonary circulation must be evaluated.

Anesthetic considerations

If kyphosis is severe, a chest radiograph should be obtained. Lung function tests are most likely difficult to perform on these mentally delayed patients. Echocardiography may not only be required to exclude structural cardiac lesions, but also to determine the presence of signs of cor pulmonale. Central neuraxial anesthesia techniques may be difficult to perform due to the vertebral anomalies. Patient cooperation could be limited secondary to mental retardation. The presence of craniofacial anomalies must be taken into consideration in preparation for airway management. Sedative and/or anxiolytic premedication and the presence of the primary caregiver for induction of anesthesia may be helpful.

Pharmacological implications

Subacute bacterial endocarditis prophylaxis may be required. Consider interactions of anesthetics with chronic antiseizure therapy.

Other conditions to be considered

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