NEW YORK (Reuters Health) – Abdominal pain and hyponatremia in a 16-year-old girl with constipation and disordered eating confounded the diagnosis of a much less common condition, acute intermittent porphyria (AIP), according to a case report published online December 5 in Pediatrics.
Dr. Terrell Stevenson and colleagues from Stanford University School of Medicine, in California, describe a previously healthy 16-year-old girl who presented to the emergency department reporting 1 week of abdominal pain and constipation and several episodes of nonbloody, nonbilious emesis that began several days after she had reduced her caloric intake in an effort to lose weight.
Other than an abdomen that was tender to palpation, but without rebound tenderness or peritoneal signs, her examination was normal. Her blood count, liver function tests, and lipase also were within normal limits, but she was found to have hyponatremia (sodium level, 122 mEq/liter) with a urine specific gravity at the lower end of the normal range (1.008).
Her hyponatremia improved with isotonic intravenous fluids, but after her initial diagnosis of constipation was treated with bowel cleanout, her sodium level declined to 119 mEq/liter, leading the clinicians to suspect the syndrome of inappropriate secretion of antidiuretic hormone (SIADH).
The girl’s hyponatremia resolved after she was given a bolus of 3% hypertonic saline, followed by fluid restriction to two-thirds maintenance of 5% dextrose in normal saline.
Her abdominal pain persisted after her bowel cleanout, and attempts at tapering her patient-controlled Dilaudid analgesia failed.
Adolescent medicine and child psychiatry consultations uncovered several stressors, including the suicide of her brother, who was diagnosed with schizophrenia, 9 months earlier, as well as her history of disordered eating and anxiety.
The constellation of symptoms (abdominal pain, hyponatremia, and psychiatric symptoms) led to consideration of acute intermittent porphyria (AIP) as an all-encompassing diagnosis. Quantitative urine porphobilinogen test results showed elevation at 284.6 mmol/liter (normal range, 0-8 mmol/liter).
Genetic testing confirmed AIP with a deleterious heterozygous sequence change in the hydroxymethylbilane synthase (HMBS) gene.
The patient was discharged with instructions to maintain a high-carbohydrate diet, and since then she has had only one brief subsequent hospitalization for an AIP flare. Smaller flares have been managed successfully as an outpatient.
More-severe AIP attacks can be effectively managed with intravenous hemin, which leads to a reduction in porphyrin precursors because of negative feedback, according to the report.
Treatment also includes prevention, with education about triggers, one of the most common of which is starvation, a likely contributor to this patient’s first episode of AIP.
“This case highlights the importance of considering ‘zebras’ when the signs and symptoms of a clinical case do not match the more common diagnoses,” the researchers conclude. “This case also highlights the inherent challenge of diagnosing and treating AIP in the adolescent population, in which abdominal pain and psychiatric complaints are relatively common and disordered eating, alcohol, and substance use can be triggers for acute attacks of AIP.”
Dr. Stevenson did not respond to a request for comment.
SOURCE: http://bit.ly/2iXcxrv
Pediatrics 2017.
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