HMG CoA lyase deficiency

Overview

A rare inherited metabolic disorder where deficiency of a particular enzyme impairs the processing of amino acids in food to create energy and causes various symptoms. Stresses on the body such as infection, fasting and heavy exercise can trigger an episode

Symptoms

* Vomiting * Cyanosis * Lypothymia * Lethargy * Metabolic acidosis * Low blood sugar * Low blood sugar * Metabolic acidosis * Lack of ketone production * Dehydration * Convulsions

Causes

Metabolic alkalosis results from loss of acid, retention of base, or renal mechanisms associated with decreased serum levels of potassium and chloride. Causes of critical acid loss include vomiting, nasogastric (NG) tube drainage or lavage without adequate electrolyte replacement, fistulas, and the use of steroids and certain diuretics (furosemide, thiazides, and ethacrynic acid). Hyperadrenocorticism is another cause of severe acid loss. Cushing’s disease, primary hyperaldosteronism, and Bartter’s syndrome, for example, all lead to retention of sodium and chloride, and urinary loss of potassium and hydrogen. Excessive base retention can result from excessive intake of bicarbonate of soda or other antacids (usually for treatment of gastritis or peptic ulcer), excessive intake of absorbable alkali (as in milk-alkali syndrome, often seen in patients with peptic ulcers), administration of excessive amounts of I.V. fluids with high concentrations of bicarbonate or lactate, or respiratory insufficiency — all of which cause chronic hypercapnia from high levels of plasma bicarbonate.

Treatment

* If primary respiratory process identified, then treat the cause and the acidosis will resolve over time * Dehydration: Oral or IV fluid replacement; even with normalization of fluid status, improvement in serum bicarbonate may not occur for 2–3 days + For primary metabolic process –Estimate deficit =20 – [HCO3] ×Weight (kg) ×0.5 –Replace over 24–48 hours with oral bicarbonate (e.g. bicitra solution 1 cc =1 meq) or IV bicarbonate added to IV fluids; IV sodium bicarbonate “boluses” should be avoided unless acidosis is severe or symptomatic * Increased AG acidosis: Identify and treat cause * Distal or proximal RTA: Usually requires bicarbonate supplementation * Hyperkalemic RTA: Correct serum bicarbonate, increase fluids to improve sodium delivery to distal tubule to enhance potassium secretion