Aldolase A deficiency
A rare metabolic disorder causing hemolytic anemia and myopathy.
Aldolase A deficiency is a rare inherited metabolic condition passed down in an autosomal recessive pattern. It stems from a shortage of the aldolase A enzyme, which is mainly found in red blood cells and muscle tissue. This shortage can cause hemolytic anemia and, in some cases, muscle disease marked by exercise intolerance and rhabdomyolysis.
Because aldolase A plays a crucial role in glycolysis and is expressed almost exclusively in blood and skeletal muscle, severe mutations are rarely seen in live births; the condition is poorly documented, with only five well-described cases. Diagnosis relies on measuring reduced aldolase A enzyme activity, though symptoms and underlying causes vary.
All patients show blood-related problems. Congenital nonspherocytic hemolytic anemia is typically diagnosed at birth, involving premature red blood cell destruction without obvious shape changes. Red blood cells depend on anaerobic glycolysis for ATP, so disruption of this pathway upsets membrane ion gradients, leading to instability and cell rupture. This shortened lifespan and increased destruction cause hyperbilirubinemia, often seen as jaundice from excess hemoglobin breakdown. Cell rupture from hemolysis or rhabdomyolysis can also release high levels of potassium into the blood, raising the risk of dangerous hyperkalemia. Glycolysis also produces 2,3-diphosphoglycerate, which helps regulate hemoglobin’s oxygen affinity; its dysregulation may affect oxygen delivery and cause organ hypoxia. Findings on this metabolite are inconsistent—one Japanese patient had elevated levels, while a Jewish Canadian boy had below-average levels. Glucose metabolism is also tied to the pentose phosphate pathway, which generates NADPH for synthetic processes and reduced glutathione to protect red cells from oxidant damage. Accumulation of fructose-1,6-bisphosphate can inhibit glucose-6-phosphate dehydrogenase, an essential enzyme in that pathway. Lactate buildup has been noted in some patients, possibly linked to reciprocal stimulation of pyruvate kinase.
In some patients, a more severe form of the deficiency causes myopathy, first noticed as muscle weakness and exercise intolerance, likely from ATP depletion. This muscle breakdown, or rhabdomyolysis, can raise blood creatine phosphate levels and worsen hyperkalemia.
Delayed growth and development have been seen in some cases, possibly
- inheritance
- Autosomal recessive
- affected_enzyme
- Aldolase A
- primary_tissues
- Red blood cells and muscle tissue
- first_recorded_case
- 1973 (Beutler et al.)
- known_for
- Congenital nonspherocytic hemolytic anemia and myopathy
Lore & Background
The first recorded case of Aldolase A deficiency was described in 1973 of a Jewish Canadian boy of Romanian descent, whose parents were first cousins. Two familial male patients reported in 1981 were from a small Japanese island, also suggesting possible consanguinity. Two other cases documented in 1996 and 2004 lacked evidence for contiguity and demonstrated additional myopathic complaints.
Reader's Guide
Aldolase A deficiency is significant as a rare inborn error of glycolysis that highlights the essential role of aldolase A in red blood cell and muscle energy metabolism. The disorder's low incidence is attributed to aldolase A's essential glycolytic role and exclusive expression in blood and skeletal muscle, preventing severe mutations in successful embryos. Diagnosis is through reduced aldolase A enzymatic activity, though physiological response and fundamental causes vary. The condition presents with congenital nonspherocytic hemolytic anemia in all patients, and in some cases myopathy with exercise intolerance and rhabdomyolysis. Sequence analysis of three patients revealed distinct alterations at highly conserved regions, including a conversion of aspartic acid to glycine at residue 128, a charge disruption at residue 209, and a maternal missense mutation with paternal nonsense mutation at arginine 303. The initial 1973 case showed no structural abnormality, suggesting disordered regulation or rapid tetrameric inactivation. The disorder's rarity and variability complicate generalization of symptoms and causes.
Did You Know?
- The first recorded case was described in 1973 of a Jewish Canadian boy of Romanian descent whose parents were first cousins.
- Two familial male patients reported in 1981 were from a small Japanese island, indicating possible consanguinity.
- One patient had elevated 2,3-diphosphoglycerate levels while another had below-average levels, showing the variability of this condition.
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