Serum erythropoietin levels may be inappropriately low in the acute neuropsychiatric porphyrias.

Background: Patients with the acute porphyrias may develop renal failure and autonomic dysfunction. Renal damage and sympathetic failure may both cause erythropoietin (EPO) deficiency. In this study, we have investigated serum erythropoietin levels and autonomic function in patients with acute porphyria in clinical remission.

Methods: Serum erythropoietin levels and the corresponding haemoglobin (Hb) were assayed in 31 patients with acute porphyria and were compared to 15 type 1 diabetic patients with autonomic neuropathy, 23 patients with iron-deficiency anaemia and 18 healthy individuals.

Results: 9 out of 31 porphyric patients showed a normochromic normocytic anaemia with normal ferritin levels. Three patients had borderline-raised serum creatinine levels, and one of them was anaemic. Autonomic function was investigated in seven patients, six of them being anaemic, and the results were normal. Patients with iron-deficiency anaemia showed the expected increase in serum erythropoietin levels in response to a decreasing haemoglobin (r=-0.86, p<0.001). Patients with porphyria had inappropriately low serum erythropoietin levels for the degree of anaemia compared to iron-deficiency patients (p<0.001) although there was still a significant increase in serum erythropoietin with decreasing haemoglobin levels (r=-0.46, p=0.01). In contrast, diabetic autonomic neuropathy patients demonstrated a significant decrease in serum erythropoietin with decreasing Hb levels (r=+0.53, p=0.05).

Conclusions: Patients with acute porphyria may have inappropriately low levels of EPO. In contrast to the diabetic patients, this does not appear to be due to autonomic neuropathy but it may reflect mild renal tubular impairment.