Meckel-Gruber Syndrome (MKS)

Characterized by postaxial polydactyly and central nervous system malformation (encephalocele, severe hydrocephalus), large polycystic kidneys, and liver failure (fibrosis). Other clinical features include microcephaly, abnormality of the larynx and tongue, severe mandibular micrognatism, obesity, and cleft lip/ palate. Associated abnormalities include oral clefting and genital anomalies. Pulmonary hypoplasia is the leading cause of death.

Meckel Syndrome; Gruber Syndrome; Dysencephalia Splanchnocystica; MKS.

Genetic disorder characterized mainly by encephalocele, polydactyly, and polycystic kidneys, but with a wide phenotypic variation.

Worldwide incidence of Meckel-Gruber syndrome varies from 1:13,250-140,000 live births. There is a predilection for the Finnish population, in whom the birth incidence is 1:9000. More than 200 cases have been described in the literature.

Autosomal recessive; a gene has been identified on chromosome 17q21-q24.

It has been suggested that a failure of mesodermal induction causes MKS. The induction cascades of early morphogenesis involve numerous growth factors, homeobox genes, and paired domain genes.

Some authors consider that the minimal diagnostic criteria for the syndrome consist of cystic dysplasia of the kidney, fibrotic changes of the liver, and occipital encephalocele. Thus histologic studies are needed to confirm the diagnosis. Clinical features are highly variable among patients.

The main features are central nervous system malformations consisting usually of occipital encephalocele (with holoprosencephaly, agenesis of corpus callosum and/or hydrocephalus); seizures; postaxial polydactyly always involving the hand and occasionally the feet and polycystic kidneys; other urologic anomalies include absent or hypoplastic ureters or bladder. Often the liver shows cystic changes with duct proliferation and fibrosis. Other anomalies include microcephaly, microphthalmia or anophthalmia, cleft lip and/or palate, genital anomalies, lung hypoplasia, and congenital heart disease such as atrial septal defect (ASD), ventricular septal defect (VSD), coarctation of the aorta, and patent ductus arteriosus (PDA). Patients also present a typical “Meckel appearance” with micrognathia, flat nose, hypertelorism, a sloping forehead, wide mouth with full lips, low-set ears, and short neck.

A complete medical history must be obtained. Assess the neurological system, especially for seizures and the presence of encephalocele and raised intracranial pressure. The renal function must be evaluated. Because of the facial anomalies, the airway must be carefully examined. Finally, the cardiac system needs a thorough examination because of the high incidence of congenital heart defects. An ECG and echocardiogram must be obtained. Medications should be continued until the morning of surgery.

It is highly improbable that children with Meckel syndrome will come to the operating room. If they do, remember that all the main systems, such as the heart, liver, kidneys, and lungs, may be involved, so these children can be very unstable. Also, they present many features, such as micrognathia, short neck, and occipital encephalocele that can render intubation difficult.

Implications are related to decreased renal and liver function in the setting of neonatal anesthesia.