Weight loss in a baby proved to have a genetic link

Unexpected loss of weight in a baby turned out to have a serious cause, writes Dr Julia Markham

I should have been a bit suspicious when the midwife left a message asking me to visit a 10-day-old baby with weight loss. When I arrived at the house I realised that this was the home of two healthcare professionals.  

The baby boy had been born by Caesarean section at full-term after a straightforward pregnancy. His two-year-old sister was a normal little girl with moderate eczema.  

The baby’s weight had dropped from 4.37kg at birth to 3.86kg, and he had vomited a few times.  

He seemed hungry, was not sleepy or jaundiced, and was passing plenty of urine. I did not notice anything out of the ordinary on examining him.  

I had a chat with his parents about feeding and winding, and reiterated the fact that babies do not always follow the centile lines on the growth charts.  

Underlying concerns  

I asked them if they were worried about any underlying medical conditions that I might not have thought of. The mother mentioned pyloric stenosis. We made a plan to review the baby in 48 hours, or earlier if necessary.  

When I returned to the surgery after the rest of my home visits, there was a message from the mother to say that the baby had produced a large vomit and did not seem well.  

Although I was still not overly concerned, I started to consider other possible diagnoses and arranged for a second opinion at our local hospital.  

On admission the baby was noted to have a pigmented scrotum and changes in U&Es.  

Within 12 hours he had been diagnosed with congenital adrenal hyperplasia (CAH) and was being treated with an infusion of saline solution and steroids.  

CAH is a group of inherited autosomal recessive disorders caused by the absence of essential enzymes in the pathway of cortisol and aldosterone synthesis, leading to excessive ACTH release.  

The most common variant is 21-hydroxylase deficiency, which affects about one in 5,000 live births.  

Adrenal crisis 

Affected females are virilised at birth. Prompt recognition is less easy in males, who may not be diagnosed until they have an adrenal crisis in the second week of life. Their genitalia are normal. Usually CAH in boys is misdiagnosed as gastroenteritis or pyloric stenosis.  

The crisis is often preceded by vomiting and poor weight gain, and is characterised by low serum sodium and high potassium. Grossly raised ACTH and 17-hydroxyprogesterone levels suggest 21-hydroxylase deficiency. A salt-losing crisis demands urgent therapy with IV saline, glucose and hydrocortisone.  

The long-term management plan must aim to suppress the hyperplastic adrenal glands and to provide replacement hydrocortisone and fludrocortisone. Children with ambiguous genitalia should have their karyotype done to establish their chromosomal sex.     

Children should be managed by specialist endocrinologists to help ensure that they have normal growth. Mild cases might go unrecognised until teenage years or early adulthood. Severe cases might be fatal if untreated.  

Affected girls should have their virilised perineum corrected in the first year of life. The outlook is excellent and affected adults can have normal fertility.  

Happily, my patient was home within a few days and now has regular follow-ups at our local specialist clinic.    

Dr Markham is a GP in Solihull, West Midlands  

Lessons learnt  

  • Although weight loss and vomiting are common in newborn babies, they can be signs of serious disease.  
  • Careful examination is important.  
  • Always ensure patients know to call back promptly if concerned.  
  • Rare cases of adrenal hyperplasia do occur and may not be diagnosed in boys until the second week.

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