Nephrocalcinosis and urolithiasis in carbonic anhydrase II deficiency syndrome

We report three new Kuwaiti patients with carbonic anhydrase II deficiency (CA II) from two unrelated families. Each patient had osteopetrosis, distal renal tubular acidosis, and cerebral calcification. Patients from family 1 (a brother and a sister) had some facial anomalies and delayed development. At the age of 14 months, ultrasound studies in the girl showed medullary nephrocalcinosis which has not been previously described in association with CA II, while cerebral CT scan revealed dilated ventricles. The patient from family 2, who had two previously reported affected siblings, developed bilateral recurrent renal stones and hypercalciuria but no nephrocalcinosis. None of his affected siblings had nephrocalcinosis or urolithiasis. DNA analysis of patients from both families showed that each of them was homozygous for the "Arabic" mutation in the CA II gene. We report new features in three Arab patients with CAII deficiency. Also review all previously reported CA II cases from Kuwait in order to highlight the inter-/intra-familial variability of the disease in this part of the world despite the overwhelming prevalence of the same "Arabic" mutation among the patient population.