Chronic polyneuropathy in the elderly is usually attributed to various acquired causes such as idiopathic (one-third), diabetes, nutritional deficiency, toxic (alcohol-related and drug-induced), immune-mediated such as chronic inflammatory demyelinating polyneuropathy (CIDP) or its variants, inflammatory, infective, and paraneoplastic conditions. [1] On the other hand, a genetic etiology is less likely as noted in 3.4% by Mathis et al. [1] Also, 94% present as axonal neuropathies in the elderly compared to only 6% as demyelinating neuropathies.

Late-onset urea cycle defects are rarely reported in literature. All urea cycle defects are autosomal recessive except for ornithine transcarbamylase (OTC) deficiency, which is X-linked recessive and is the most common with an estimated prevalence of 1:140000. [2] These patients develop clinical features of encephalopathy in stressful situations such as increased catabolism due to seizures, decreased food intake, gastrointestinal bleeding, infections, and drugs like valproic acid, salicylates and carbamazepine. Here we present a case highlighting a rare presentation of late onset urea cycle defect and the challenges to its recognition.