Index of SuspicionCase 1: Acute Urinary Retention in a 13-month-old BoyCase 2: Depression in the Scalp of a 5-year-old BoyCase 3: Acute Onset of Abnormal Behavior in a 16-year-old BoyCase 4: Dark Urine in a 2-year-old Boy

A 13-month-old white boy presents to the emergency department (ED) with sudden onset of abdominal discomfort and lethargy. There is no history of fevers, vomiting, or diarrhea. He was born at 39 weeks’ gestation by spontaneous vaginal delivery. He has had no surgery, and he does not take any medications. His immunizations are up to date and he is developmentally appropriate. Some older family members have had gastric, uterine, and cervical cancers. Physical examination reveals a crying but consolable child. He is afebrile with a heart rate of 123 beats per minute, blood pressure of 107/60 mm Hg, respiratory rate of 37 breaths per minute, and oxygen saturation of 97% on room air. His abdomen is soft and nontender, with mild guarding; there are no masses or hepatosplenomegaly. Neurologic examination reveals normal strength and deep tendon reflexes. A rectal examination is deferred because of parental request. His laboratory results reveal a serum sodium level of 134 mmol/L, potassium of 4.4 mmol/L, chloride of 105 mmol/L, bicarbonate of 13 mmol/L, blood urea nitrogen of 83 mg/dL, creatinine of 5.4 mg/dL, glucose of 98 mg/dL, calcium of 8.6 mg/dL, and lipase of 24 U/L. The complete blood count is normal for age, and urinalysis on a catheterized specimen shows moderate occult blood, but is negative for protein, leukocyte esterase, or nitrites. He receives intravenous fluids to correct his pre-renal kidney failure. Subsequently, he develops urinary retention that requires frequent urinary catheterizations. Renal ultrasonography shows bilateral hydronephrosis, and a voiding cystourethrogram shows two small bladder diverticulae and the absence of spontaneous emptying of the bladder. An advanced imaging study reveals the diagnosis. A 5-year-old boy is brought to the clinic by his new foster mother for evaluation of a depression in his scalp noticed recently during bathing. The child has been living in …