Pathological and biochemical studies of mucopolysaccharidosis type IIIB (Sanfilippo syndrome type B) in juvenile emus (Dromaius novaehollandiae).

Abstract

Mucopolysaccharidosis (MPS) type IIIB was diagnosed in 14 juvenile emus (Dromaius novaehollandiae), ages 3 weeks to 6 months, based on pathological and biochemical analyses. The animals had a history of neurological signs or sudden death; one of the birds with neurological signs and 3 others experienced acute hemoabdomen. Histopathologically, neuronal swelling and vacuolation in the cerebrum, cerebellum, brainstem, and spinal cord (80%-92%); retina (100%); autonomic ganglia of the intestine (71%); gizzard (50%); adrenal gland (27%); and ear (50%) were noted in affected but not healthy emus. Cytoplasmic vacuoles were also observed in the pancreas, liver, intestine, adrenal glands, and kidneys. The intracytoplasmic inclusions were periodic acid-Schiff and Luxol Fast Blue positive, consistent with a storage disease. Foamy macrophages infiltrated the liver, intestine, tunica media of the aorta, and spleen. By transmission electron microscopy, typical lamellated cytoplasmic bodies were detected in neurons of the brain and retina, while electron-dense bodies consistent with glycosaminoglycan inclusions were observed in hepatocytes and/or hepatic macrophages. The livers of the 2 affected emus studied contained large amounts of heparan sulfate, which is suggestive of MPS type III. Compared with normal controls, hepatic and serum α-N-acetylglucosaminidase activity was very low (<8% of control), while other enzyme activities were normal to increased in the 2 affected emus studied. Moreover, affected emus were homozygous for a 2-bp deletion in the NAGLU gene. This study characterizes the pathology of MPS type IIIB in emus, which is one of the rare inborn errors in birds, showing the homology of this condition to Sanfilippo syndrome in humans.