A 4-day-old boy presents to the pediatrician with his mother for his 1st well visit. The patient was born at 36 weeks gestation to a 26-year-old primigravid mother via cesarean section for cervical incompetence. The patient required no resuscitation at birth and both mother and child were discharged from the hospital at 2 days of life. The patient has been exclusively breastfed since birth, and his mother reports that he feeds for 20-30 minutes every 2 hours. The patient urinates 7 times per day and has begun passing 2-3 stools per day that his mother describes as “grainy” and the color of “mustard.” His birth weight was 3670 g (8 lb 1 oz), and his current weight is 3487 (7 lb 11 oz). His temperature is 97.1°F (36.2°C), blood pressure is 57/42 mmHg, pulse is 140/min, and respirations are 38/min. On physical exam, the patient’s anterior fontanelle is soft and flat, and his eyes are moderately icteric. His abdomen is soft and non-distended. The patient has the physical exam finding seen in Figure A. His diaper can be seen in Figure B. Laboratory studies reveal the following:

Total bilirubin: 13 mg/dL
Conjugated bilirubin: 0.6 mg/dL

Which of the following is the most appropriate next step in management?
Order serum uric acid concentration
Continue current breastfeeding regimen
Order spot uric acid to creatinine ratio
Administer intravenous hydration
Continue current breastfeeding regimen
This patient presents at day 4 of life with weight loss of 5% of his birth weight, uric acid crystals in his diaper, desquamation of the palms and soles, and unconjugated hyperbilirubinemia, which are normal findings in a newborn. The most appropriate next step in management is continuing his current breastfeeding regimen.

Healthy newborns may lose up to 7% of their birth weight in the first 5 days of life and exhibit dry, peeling skin on the palms and soles as the skin adapts to a drier environment outside the womb. Uric acid crystals that look like “brick dust” are also a normal finding in the diaper during the 1st week of life, as uric acid excretion is highest at birth. All newborns should be evaluated for signs of dehydration, including sunken fontanelles, dry mucous membranes, low urine output, excessive weight loss, and tachycardia. If these findings are not present, continued breastfeeding should be encouraged.

Westerfield et al. review the evidence regarding the benefits of breastfeeding. They discuss how breastfeeding is associated with decreased risk of atopic dermatitis and gastroenteritis. They recommend ensuring proper breastfeeding techniques.

Figure A demonstrates flaking and peeling of the soles (red circles), which is a normal finding in the 1st week of life.

Figure B demonstrates uric acid crystals (“brick dust”) in the diaper (red circle), which is another normal finding that is caused by high uric acid excretion in the 1st few days of life.

Incorrect Answers:
Answer A: Administering intravenous hydration would be appropriate for a severely dehydrated neonate who cannot tolerate hydration orally. This patient is not exhibiting signs of dehydration.

Answer C: Ordering a serum uric acid concentration may be part of an evaluation for Lesch-Nyhan syndrome, an X-linked recessive disorder of purine metabolism caused by deficiency of the enzyme hypoxanthine-guanine phosphoribosyltransferase (HGPRT) that causes hyperuricemia and hyperuricosuria. The uric acid crystals found in this patient’s diapers are a normal finding in the 1st week of life. Treatment is supportive including allopurinol for gout.

Answer D: Ordering a spot uric acid to creatinine ratio would be an appropriate first step in evaluation for Lesch-Nyhan syndrome, but the uric acid crystals in this patient’s diaper are not concerning for Lesch-Nyhan syndrome. Treatment is supportive as well as with allopurinol for gout.

Answer E: Recommending increasing the frequency of breastfeeding would be appropriate for a dehydrated infant with excessive weight loss, but this patient’s weight loss is within the expected limits for the 4th day of life.

Bullet Summary:
Healthy newborns may present with desquamation of the skin and uric acid crystals in the diaper and continued breastfeeding should be encouraged if no signs of dehydration are present.