Parathyroid hormone resistance and B cell lymphopenia in propionic acidemia

The mechanisms of hypocalcemia, recurrent infections and hypogammaglobulinemia associated with metabolic decompensation of propionic acidemia due to propionyl-CoA carboxylase deficiency have not been defined. A 7-week-old infant with this disorder presented with severe hypocalcemia and B cell lymphopenia during an episode of metabolic acidosis and hyperammonemia. Hypocalcemia (1.1 mmoll ¹) was associated with elevated serum intact parathyroid hormone (122 ng 1 ¹), hyperphosphatemia, hypophosphaturia and hypercalcuria, indicating parathyroid hormone resistance. B cell lymphopenia (20 cells μl^-1) was associated with transient neutropenia, anemia and subsequent hypogammaglobulinemia (IgG < 294mgdl^-1, IgM < 8mgdl^-1, IgA < 8mgdl ¹), while T cells were normal. Parathyroid hormone resistance and B cell lymphopenia resolved following treatment with hemodialysis, diet and carnitine. These complications may be due to interference with parathyroid hormone renal tubular action and B cell maturation/proliferation by accumulated organic acids.