Symptoms and Diagnosis of Renal PHA1

The symptoms of Renal Pseudohypoaldosteronism Type 1 (Renal PHA1) often appear suddenly in the first few days or weeks of life ^[1][2]. Because the kidneys are losing salt, the body’s delicate chemical balance is disrupted, leading to a “salt-wasting crisis” that requires immediate medical attention.

Signs and Symptoms in Infancy

Most babies with Renal PHA1 appear healthy at birth but begin to show signs of distress between day 3 and day 14 of life ^[1][3]. The most common symptoms include:

• Poor Feeding and Failure to Thrive: Difficulty waking for feeds or not gaining weight as expected ^[4][5].
• Vomiting: Often mistaken for severe reflux or a stomach bug ^[4].
• Lethargy: Extreme sleepiness or a “floppy” appearance.
• Dehydration WARNING: Because the kidneys are actively flushing out salt and water, a baby with Renal PHA1 may continue to have plenty of wet diapers even when dangerously dehydrated. Do not rely on wet diapers as a sign of hydration. Instead, watch for rapid weight loss, extreme lethargy, or a sunken “soft spot” (fontanelle) on the head ^[6].

The Biochemical “Signature”

To diagnose Renal PHA1, doctors look for a specific pattern in the blood and urine. When the kidneys ignore aldosterone, they fail to keep sodium and fail to get rid of potassium ^[7][8]. This creates a unique biochemical profile:

• Hyponatremia (Low Sodium): The blood does not have enough salt because it is being flushed out in the urine ^[6][9].
• Hyperkalemia (High Potassium): Potassium levels rise to dangerous levels because the kidney cannot “pump” it out ^[6][7].
• Metabolic Acidosis: The blood becomes too acidic, which can make the baby breathe faster to compensate ^[9][10].
• High Renin and High Aldosterone: This is the “smoking gun.” In most conditions, if salt is low, the body makes more aldosterone to fix it. In Renal PHA1, the body makes massive amounts of aldosterone, but because the kidneys are resistant, the levels just keep climbing ^[11][7].

Renal PHA1 vs. CAH: The Newborn Screen False Alarm

When a newborn has low sodium and high potassium, doctors often first suspect Congenital Adrenal Hyperplasia (CAH) ^[9][12]. Many parents get a terrifying phone call about a positive Newborn Screening (NBS) test for CAH. However, both conditions look identical in early symptoms, but the treatments are completely different.

In CAH, the body cannot make enough hormones. In Renal PHA1, the body makes too much aldosterone but cannot use it ^[6][9]. Doctors use a test called 17-hydroxyprogesterone (17-OHP) to definitively rule out CAH; if this level is normal but aldosterone is extremely high, Renal PHA1 becomes the primary suspect ^[6][11].

Confirming with Genetics

While the blood tests point to the diagnosis, genetic testing of the NR3C2 gene provides the final confirmation ^[13][14]. This test looks for a “spelling error” in the gene that builds the kidney’s salt-saving receptors. Finding a mutation here confirms it is the renal-only form, which carries the reassuring news that the condition will likely resolve as the child grows ^[14][15].

Diagnosis Checklist

Review your child’s lab reports for these key markers. If any are missing, ask your doctor for the results.

• [ ] Sodium Level: (Looking for Low)
• [ ] Potassium Level: (Looking for High)
• [ ] Bicarbonate/CO2: (Looking for Low, indicating acidosis)
• [ ] Aldosterone: (Looking for Extremely High)
• [ ] Plasma Renin Activity (PRA): (Looking for Extremely High)
• [ ] 17-OHP: (Should be Normal to rule out CAH)
• [ ] NR3C2 Genetic Test: (Ordered or completed)

For more on how to manage these symptoms daily, see [-1](“Introduction to Renal PHA1”) or Treatment and Daily Management.