Table 1.
Characteristics of the Two Patients.*
| Characteristic | Patient 1 | Patient 2 | Age-Matched Controls |
|---|---|---|---|
| Age at presentation (mo) | 3.0 | 2.5 | — |
| Clinically significant findings | Irritability | Generalized seizures | — |
| Blood pressure (mm Hg) | |||
| Systolic | 80–128 | 93–118 | 108† |
| Diastolic | 34–92 | 37–57 | 66† |
| Serum and plasma studies | |||
| Sodium (mmol/liter) | 123 | 118 | 134–143 |
| Potassium (mmol/liter) | 4.6 | 4.7 | 3.4–4.9 |
| Chloride (mmol/liter) | 91 | 86 | 98–107 |
| Bicarbonate (mmol/liter) | 28 | 21 | 23–32 |
| Creatinine (mg/dl) | <0.3 | 0.3 | 0.3–0.7 |
| Urea nitrogen (mg/dl) | <5 | 3 | 8–23 |
| Aldosterone (ng/dl) | 10 | 24‡ | 6–68 |
| Plasma renin activity (ng of angiotensin 1/ml/hr) | 3.8 | <1‡ | <15 |
| Osmolality (mOsm/kg) | 252 | 247 | 285–293 |
| AVP (pg/ml) | <1 | <1‡ | 1.0–13.3 |
| Thyrotropin (mIU/liter) | 0.77 | 4.58 | 1.7–9.1 |
| Free thyroxine (ng/dl) | 1.09 | 0.97 | 0.8–1.8 |
| Cortisol (μg/dl) | |||
| Baseline | 13.3 | 10.3, 43§ | 4–20 |
| 60 Min after intravenous synthetic corticotropin (15μg/kg) | 36.5 | — | >20 |
| Coagulation studies | |||
| von Willebrand factor antigen (%) | 104 | 100 | 46–155 |
| Ristocetin cofactor (%) | 108 | 65 | 56–155 |
| Factor VIII activity (%) | 153 | 123 | 50–150 |
| Fibrinogen (mg/dl) | 198 | 360 | 170–435 |
| D-Dimer fragment | Negative | Negative | Negative |
| Prothrombin time (sec) | 11.7 | 10.9 | 9.2–11.9 |
| Partial-thromboplastin time (sec) | 24.3 | 32.5 | 21.3–34.8 |
| Urine studies | |||
| Osmolality (mOsm/kg) | 284 | 390‡ | 300–900 |
| Sodium (mmol/liter) | 35 | 75‡ | — |
| Magnetic resonance image of the head | Normal | Pars intermedia cyst, otherwise normal | — |
| Chest radiograph | Normal | Normal | — |
To convert values for creatinine to micromoles per liter, multiply by 88.4. To convert values for urea nitrogen to millimoles per liter, multiply by 0.357. To convert values for aldosterone to nanomoles per liter, multiply by 0.0277. To convert values for AVP to picomoles per liter, multiply by 0.923. To convert values for free thyroxine to picomoles per liter, multiply by 12.87. To convert values for cortisol to nanomoles per liter, multiply by 27.59. To convert values for fibrinogen to micromoles per liter, multiply by 0.0294.
Measurement is given for the 95th percentile.
The value was obtained during an episode of hyponatremia after initial presentation.
Two baseline levels were obtained on separate occasions.