Unrecognized citrullinemia mimicking encephalitis in a 14 year-old boy – the role of a standardized lumbar puncture protocol

Citrullinemia is a urea cycle disorder caused by deficiency of argininosuccinate synthetase. Late onset forms can go undiscovered until a decompensation episode that can resemble encephalitis.

Herein we report a fourteen year old patient with an acute episode with reduced level of consciousness and confusion interpreted as encephalitis. EEG mainly showed bilateral slowing with some spikes plus spike waves and was interpreted as suspicious for encephalitis. Brain MRI was normal. Leucocytes in CSF were slightly elevated. Treatment for a CNS infectious disease was begun with aciclovir and ceftriaxone. Because symptoms did not resolve and there were some episodes of confusion, a repeat lumbar puncture was performed this time according to a standardized protocol including a metabolic screening with amino acid profile. An elevation of citrulline in CSF was found, which ultimately led to the diagnosis of a late onset citrullinemia. The establishment of this diagnosis will protect the patient from the sequelae of unrecognized and thus untreated episodes of hyperammonemia.

Thus, following a standardized lumbar puncture protocol is essential to detect patients with otherwise unrecognized underlying disorders.