A newborn baby presents with shock, hyperkalemia and hypoglycemia. What is the most likely diagnosis
First, shock in a newborn can have various causes like sepsis, congenital heart defects, or metabolic disorders. Hyperkalemia and hypoglycemia add to the clues. Hyperkalemia could be due to cell lysis or impaired excretion. Hypoglycemia might be from lack of glucose production or excessive consumption.
What conditions present with all three? Congenital adrenal hyperplasia (CAH) comes to mind. CAH, especially 21-hydroxylase deficiency, leads to cortisol and aldosterone deficiency. Aldosterone deficiency causes salt-wasting, leading to hypovolemic shock. The lack of cortisol can cause hypoglycemia. Hyperkalemia occurs because aldosterone is low, reducing potassium excretion.
Another possibility is adrenal insufficiency. But in newborns, CAH is a classic cause. Other options like sepsis might cause shock but not typically hyperkalemia and hypoglycemia together. Hypoglycemia in sepsis is possible, but hyperkalemia isn't typical unless there's cell breakdown.
So, the correct answer is Congenital Adrenal Hyperplasia. The other options like sepsis, heart defects, or metabolic disorders might not fit all three symptoms. The key here is the combination of salt-wasting, hyperkalemia, and hypoglycemia pointing to adrenal insufficiency in CAH.
**Core Concept**
This question tests understanding of **congenital adrenal hyperplasia (CAH)**, specifically 21-hydroxylase deficiency, a common autosomal recessive disorder. It involves **aldosterone and cortisol deficiency**, leading to **salt-wasting crises**, **hyperkalemia**, and **hypoglycemia** due to impaired gluconeogenesis.
**Why the Correct Answer is Right**
In **21-hydroxylase deficiency**, the **21-hydroxylase enzyme** is defective, blocking cortisol and aldosterone synthesis. This causes **adrenal crisis** in newborns, with **hypovolemic shock** (due to aldosterone deficiency), **hyperkalemia** (reduced renal potassium excretion), and **hypoglycemia** (cortisol deficiency impairs gluconeogenesis). Classic presentation includes **salt-wasting** and **ambiguous genitalia** in females.
**Why Each Wrong Option is Incorrect**
**Option A:** *Sepsis* causes shock and hypoglycemia but typically **not hyperkalemia** unless there is severe cell lysis.
**Option B:** *Congenital heart disease* leads to cardiogenic shock but does not cause **hyperkalemia** or **hypoglycemia**.
**Option C:** *Diabetic ketoacidosis* is rare in newborns and presents with **hyperglycemia**, not hypoglycemia.
**Clinical Pearl / High-Yield Fact**
Remember the **"salt-wasting crisis"** in CAH: **hyperkalemia + hypoglycemia + shock** in a newborn with ambiguous genitalia (in females) is a classic exam