Index of Suspicion

Case 1 Presentation

A 15-year-old African-American boy is seen in late February complaining of 2 weeks of “tingling and cramping in my hands and feet after basketball.” He has been well and is taking no medications. His diet consists mainly of “fast foods and cola.”

Physical examination reveals a youth who looks well. All vital signs are normal. His growth has consistently followed the 75th percentile for height and 50th percentile for weight. Physical findings are completely normal. He has sexual maturity rating stage 4 genitalia, normal cranial nerve examination results, and normal strength and deep tendon reflexes.

Initial laboratory study results include: calcium, 4.9 mg/dL (1.23 mmol/L) (normal, 8.5 to 10.2 mg/dL [2.13 to 2.55 mmol/L]); phosphorus, 4.9 mg/dL (1.58 mmol/L) (normal, 2.5 to 4.5 mg/dL [0.81 to 1.45 mmol/L]); magnesium, 1.9 mg/dL (0.78 mmol/L) (normal, 1.7 to 2.2 mg/dL [0.70 to 0.91 mmol/L]); alkaline phosphatase, 576 U/L (normal, 100 to 390 U/L); albumin, 3.6 g/dL (36 g/L) (normal, 3.6 to 5.0 g/dL [36 to 50 g/L]); and creatinine, 0.7 mg/dL (61.9 mcmol/L) (normal, 0.7 to 1.5 mg/dL [61.9 to 132.6 mcmol/L]). Thyroid-stimulating hormone, complete blood count, liver and pancreatic enzymes, and the remainder of the serum electrolytes are within normal limits.

On re-examination, the patient is noted to have an absence of Trousseau or Chvostek signs. Electrocardiography demonstrates normal sinus rhythm with a corrected QT interval of 451 ms (normal, 425 ms maximum). Radiographs of the long bones reveal no deformity, pathologic fractures, or demineralization.

Case 2 Presentation

An 18-month-old boy has a 3-day history of worsening cough, tachypnea, and increased work of breathing. He has had no fever, anorexia, vomiting, diarrhea, cyanosis, abdominal pain, or rashes. His immunizations are up to date, including influenza. He has experienced three episodes of “atypical pneumonia” involving the right middle and lower lobes, all requiring hospitalization. He …