Snyder-Robinson syndrome

Abstract

Snyder-Robinson syndrome, also known as spermine synthase deficiency, is an X-linked intellectual disability syndrome (OMIM #390583). First described by Drs. Snyder and Robinson in 1969, this syndrome is characterized by an asthenic body habitus, facial dysmorphism, broad-based gait, and osteoporosis with frequent fractures. We report here a pediatric autopsy of a 4 year old male with a history of intellectual disability, gait abnormalities, multiple fractures, and seizures previously diagnosed with Snyder-Robinson syndrome with an SMS gene mutation (c.831G>T:p.L277F). The cause of death was hypoxic-ischemic encephalopathy secondary to prolonged seizure activity. Although Snyder-Robinson syndrome is rare, the need to recognize clinical findings in order to trigger genetic testing has likely resulted in under diagnosis.

Keywords: Intellectual Disability; Mental Retardation, X-linked; Snyder-Robinson syndrome; Spermine Synthase.

Figure 1. Dysmorphic features included macrocephaly, prominent cupped ears, and protruding lower lip.

Figure 2. Photomicrography of the testes showing regularly arranged tubules. No Leydig cells are present (H&E, 20X).

Figure 3. Coronal sections of the frontal lobe (A) and at the level of the caudate and putamen (B) from the current case (top) and a normal control (bottom) demonstrate diffuse enlargement of all structures in an otherwise structurally normal brain including normal cortical lamination and neuronal organization.

Figure 4. A – section of the hippocampus shows acutely hypoxic-ischemic neurons and reactive vessels with underlying neuronal loss; B – the area of infarct corresponding to incipient uncal herniation is shown (H&E, 10X for both).