Progressive calcification of the brain and the spinal cord at early infantile onset was observed in two siblings. They showed growth failure, psychomotor deterioration, deafness, vestibular dysfunction, microcytic hypochromic anemia, abnormal ratios of lymphocyte subpopulations, and slightly decreased bicarbonate on blood gas analysis. Distal renal tubular acidosis was demonstrated in one of them. Carbonic anhydrase II activity was normal. This new hereditary disease might have a defect in a molecule that is present in brain, spinal cord, kidney and hematocytes and is involved in H+/HCO3- production or transport.