Osteopetrosis with renal tubular acidosis

Osteopetrosis with renal tubular acidosis, also known as carbonic anhydrase II deficiency syndrome or marble brain disease, is a rare autosomal recessive disorder caused by mutations in the CA2 gene encoding carbonic anhydrase II. This enzyme plays a critical role in acid-base balance in multiple organ systems, and its deficiency leads to a unique combination of osteopetrosis (abnormally dense but fragile bones), renal tubular acidosis (impaired kidney acid excretion), and cerebral calcification. The condition is sometimes referred to as Guibaud-Vainsel syndrome. The disease primarily affects the skeletal system, kidneys, and brain. Skeletal manifestations include increased bone density visible on X-rays, frequent fractures despite dense-appearing bones, short stature, and dental abnormalities. Renal tubular acidosis (both proximal and distal types) leads to metabolic acidosis, which can cause failure to thrive, muscle weakness, and growth retardation. Cerebral calcifications, particularly in the basal ganglia, may be associated with intellectual disability and developmental delay, though cognitive outcomes are variable. Some patients may also develop cranial nerve compression due to narrowed bony foramina, potentially causing visual or hearing impairment. The osteopetrosis in this condition is generally classified as an intermediate form, less severe than the infantile malignant type but more significant than the adult benign form. Treatment is primarily supportive and symptomatic, including correction of metabolic acidosis with bicarbonate supplementation, management of fractures, and monitoring for cranial nerve complications. Unlike some forms of severe osteopetrosis, hematopoietic stem cell transplantation is generally not indicated because the bone marrow is usually not severely compromised. The condition has been reported with higher frequency in populations with elevated rates of consanguinity, particularly in North Africa and the Middle East.

Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.

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