8. Case Study 7

A 20 year old female (MT) presented with a 1 week history of abdominal pain, vomiting, tinnitus, behavioral changes and lethargy. An abdominal ultrasound and brain CT scan showed no abnormality. A blood count, liver enzymes, renal function and CSF analysis were normal and a toxicology screen was negative. An EEG showed slow background rhythm

Over the following 24 hours she became increasing encephalopathic with a Glasgow coma score of 6. Acute porphyria was considered as a possible diagnosis. After a further 48 hrs a repeat CT-scan showed massive brain oedema. Plasma ammonia was then measured and was 606 µmol/l. Urine orotic acid was markedly increased. There was no increase in urine citrulline or argininosuccinic acid. Treatment was commenced with hemofiltration and IV benzoate and phenylbutyrate but she developed massive intracranial hypertension and died.

On reviewing the family history the following pedigree was ascertained:

Comment: The biochemical findings are consistent with OTC deficiency. The presentation in adulthood is consistent with a mutation associated with residual enzyme activity. This is a case of paternal transmission of a late onset form of OCT deficiency, which is often overlooked as a form of inheritance in this disorder. Reference 40 gives further details of this type of case.

It is not surprising that a member of the extended family died with a diagnosis of Reye’s syndrome as that condition, of unknown aetiology, has several symptoms in common such as vomiting, progressive confusion leading to coma, cerebral oedema, and in the late stages raised ammonia levels. Further information can found in 41.

Learning objectives from this case study:

1. To recognise and understand the mechanisim by which male transmission can occur in an X-linked disorder such as OTC
2. To note that late onset forms of OTC can present for the first time in adulthood.