Pancreas and gallbladder agenesis in a newborn with semilobar holoprosencephaly, a case report

A few hours after birth a Caucasian female was transferred to the neonatal care unit of UZ Brussels for bradycardia and recurrent hypoxia. The girl was born after a pregnancy of 38 weeks and was small at gestation (1100 gram). Pregnancy was uneventful besides intra-uterine growth retardation that could not be attributed to any specific cause. The mother had been healthy throughout the entire pregnancy and did not use medication, drugs or alcohol. Delivery was by uncomplicated caesarean section and Apgar score was 9/10/10. Seven years earlier, the mother successfully gave birth to a girl with intra-uterine and postnatal growth retardation (1.88 kg body weight at birth, 14 kg at age 8) but was otherwise normal. Both the mother and father are healthy individuals of relatively short stature (148 and 156 cm respectively) without a family history of diabetes mellitus, mental retardation or structural brain anomalies such as holoprosencephaly. The parents are not consanguineous.

Physically, the newborn appeared dystrophic with receding forehead, cylindrical nose, mild hypotelorism, dysplastic left ear, hypoplastic zygomatic bone and thumbs in adduction. Structural limb anomalies including polydactyly were absent, palate and lips normal. There were clear distinct female genitalia and the anus and rectum were normal.

Neonatal diabetes was diagnosed within 24 h after birth with blood glucose values exceeding 500 mg/dL and undetectable C-peptide values (<0.03 nmol/L). The diagnosis was not associated with ketoacidosis. Treatment consisted of intravenous insulin (1-2 IU/24 h) for 20 days after which the patient was switched to subcutaneous insulin NPH twice daily (0.5 IU twice daily). Despite intensive monitoring, glycaemic control was difficult with both hyper- and hypoglycaemia. On admission the patient received parenteral nutrition. Enteral nutrition was introduced at day 7. On this additional exocrine pancreatic insufficiency was suspected by flat, yellowish stool in which trypsin could not be detected and low amylase and lipase activity in the blood. From day 14 onwards the infant only received enteral feeding together with oral pancreatic enzymes (Creon®) that was well tolerated and resulted in weight gain. Complete absence of the pancreas was confirmed by magnetic resonance imaging. The gallbladder was not visualized but there was no evidence of jaundice. Brain ultrasound revealed the absence of the corpus callosum and immature brain development. Magnetic resonance imaging confirmed semilobar holoprosencephaly. Tests for inborn errors of metabolism showed no abnormalities and no clinical syndrome could be identified. At this point, besides a prominent sternum no additional malformations where found.

Autopsy

Informed consent from the parents was obtained before autopsy. Experienced pathologists performed the autopsy within two hours after death. After examination of the external body the internal abdominal and thoracic organs were procured and examined. To allow removal of the brain, a neuropathologist opened the skull. The pituitary gland was carefully removed from the sella turcica and the brain conserved in 10% formol. Coronal brain sections were performed two months following conservation to examine macroscopic morphology.

At autopsy the liver, spleen, stomach and duodenum were removed and examined separately. No orthotopic pancreas tissue was observed (Fig. 1a). After localisation of Vater’s ampulla the common bile duct was found but pancreatic duct, cystic duct and gallbladder were absent (Fig. 1b). A small amount of accumulation of biliary pigment in the liver was found but intra-hepatic biliary ducts and liver architecture appeared normal (Fig. 1). Heart, lungs, kidneys, adrenal glands, ureters, bladder, ovaries, uterus and muscle were normal both macro- and microscopically. The duodenum was permeable without atresia, obstruction or stenosis of the small intestine. Macroscopic analysis of the brain showed a normal cerebellum (Fig. 2a) but polymicrogyria and partial fusion of the frontal lobes were obvious (Fig. 2b and c). Temporal and occipital lobes and brainstem were normal. Rhinencephalon and the olfactory nerve were bilaterally absent but the chiasma opticum and pituitary gland were present and appeared to be normal (Fig. 2c). The anterior cerebral artery could not be identified but all other vascular structures had a normal appearance. Coronal brain sections demonstrated the absence of the inter-hemispheric fissure of the frontal lobes, frontal parts of the corpus callosum and the lateral ventricles (Fig. 2d). The more posterior parts of the corpus callosum and ventricles appeared normal as well as the thalamus, striatum, brainstem, cerebellum and occipital lobes.

We report the first case of pancreatic agenesis occurring simultaneously with HPE. Although dysmorphic, the patient did not show any other defects compatible with known clinical syndromes associated with pancreatic agenesis and did not have mutations in any of the genes where mutations have been associated with pancreatic agenesis. Neonatal diabetes including pancreatic agenesis has been associated with abnormal brain development. In many of these patients a specific monogenic defect was identified in genes encoding transcription factors that are key during pancreas/beta cell development [7, 9, 10, 16, 23, 24]. Although HPE can have many causes other than genetic defects, the absence of the pancreas in the current case report strongly suggests a monogenic defect. This is underscored by its similarity to the reported cases of PTFA1 defects [7, 20], which was not the cause of the defects seen in the present patient. The severity and combination of the underlying abnormalities suggest an early defect during embryonic development, before budding of the pancreas, possibly at the end of gastrulation, when HPE develops and the ventral endoderm is in close vicinity of the developing forebrain. Disruption of a factor at this stage required for both endoderm specification and later pancreas development as well as development of the forebrain may explain the phenotype we observed.

Pancreas formation during embryonic life is under control of a complex network of transcription factors. This developmental program is providing landmarks for those who aim to recapitulate beta cell formation from human stem cells and provide unlimited supply to treat type 1 diabetic patients. Unique patients have proven to be an outstanding opportunity for the identification of novel transcription factors involved in beta cell development and the present case may help identify a novel key regulator in beta cell development.