Patients present with renal tubular acidosis,
nephrocalcinosis, and renal failure. Hypokalemia with muscle weakness and
periodic paralysis is frequent. Polyuria, vomiting, and dehydration lead to
fluid and electrolyte imbalances.
Primary Distal Renal Tubular Acidosis; Butler-Albright
Undetermined. Females are slightly more often affected.
Autosomal dominant; however, autosomal
recessive and multiple dominant forms have been described. The disorder
most often occurs sporadically.
The primary defect is a diminished ability to
excrete hydrogen ions as ammonium and titratable acid in the distal renal
tubule, despite a low plasma bicarbonate concentration. Acidosis is the
result of the inability to excrete the full endogenous load of nonvolatile
acids, while the generation of bicarbonate is minimal.
Anorexia, vomiting, constipation, polyuria, dehydration,
and growth retardation are the main symptoms. Nephrocalcinosis is an almost
constant finding and may lead to interstitial nephritis and renal failure.
Patients are unable to achieve a urine pH below 6.0.
Onset usually occurs after age 2 years. Failure
to thrive is common. Acidosis is responsible for osteomalacia and pathologic
fractures (secondary to decreased intestinal calcium resorption), growth
retardation, and nephrocalcinosis with possible renal insufficiency.
Hyperchloremia, hypokalemia, and low serum bicarbonate are responsible for
polyuria. Hypokalemia may be severe enough to cause weakness and periodic
paralysis-like symptoms. Twenty-five percent of patients may present as a
metabolic emergency. Life-threatening dehydration can be associated with
respiratory difficulties, flaccid paralysis, cardiac arrhythmias, coma, and
circulatory collapse. Nerve deafness has been described. Despite the
potential severity of symptoms, the prognosis is good if treatment is
established early enough to prevent renal damage.
Extensive laboratory tests are
required to evaluate electrolyte levels (in blood and urine), acid-base
balance, and renal function. Administration of potassium to fully correct
hypokalemia is recommended before any correction of acidosis is initiated in
order to prevent a further fall in the potassium serum concentration
triggered by an increase in plasma pH. Acidosis is corrected with slow
administration of sodium bicarbonate. Hypocalcemia often is present, and
correction of hypokalemia and acidosis may decrease serum calcium
concentration further. Consequently, repeated boluses of intravenous calcium
may be required to prevent tetany. Because the disease is congenital,
bicarbonate supplements are a lifelong requirement. For patients undergoing
anesthesia, replace oral intake with intravenous suppletmentation.
A central venous line can be useful for
evaluating volume status but also for perioperative administration of
concentrated electrolyte solutions. Volume expansion with normal saline
solutions may paradoxically worsen the acidosis by further promoting renal
Acidosis and hypovolemia increase the
sensitivity to muscle relaxants, so close monitoring of muscle relaxation is
mandatory. Administration of thiazide diuretics may exacerbate a preexisting
hypokalemia and so must be avoided. Use of succinylcholine is best avoided
in the presence of muscle weakness secondary to the risk of a sudden and
exaggerated hyperkalemic response.
De Toni Debré Fanconi Syndrome: Rare acquired or inherited ...