ESPE Abstracts

Introduction: The carbonic anhydrase II (CA II) deficiency syndrome is a rare autosomal recessive disorder associated with osteopetrosis, renal tubular acidosis (RTA), and cerebral calcification (CADS; autosomal recessive osteopetrosis type 3). Other features include visual and auditory impairment, short stature, a large cranial vault, history of multiple skeletal fractures, developmental delay and cognitive defects, anemia, splenomegaly and secondary erythropoiesis. We report here, three siblings of CAII deficiency syndrome presenting with short stature, distal renal tubular acidosis and cerebral calcification. This is the first report of the disease occurring in three successive generations with a homozygous mutation on 8q22.

Cases: Two sisters (aged 16.5 years and 13.5 years, respectively) were referred to pediatric endocrinology department due to the history of recurrent long bone fractures (sister 1 1:3 fractures, sister 2:2 fractures). They were born to third degree consanguineous parents. Their 3 years old brother was invited for medical examination as the parents had reported him to have develeopmental delay. Birth lengths and weights of the three siblings were within normal ranges, but growth parameters of two sisters were below the 3rd percentile after 1 year of age. Motor milestones and speech development were also delayed for all of them. At presentation, the height age and bone age of sister 1 were 11 years and 16 years and of sister 2 were 10.3 and 12 years, respectively. Their brother’s height (92 cm, 25 p) and weight (14.5 kg, 50p) were in normal ranges at presentation. They all had a broad head with prominent forehead, a long bulbous nose, a relatively thin upper lip, dental carries, dental malalignment and malocclusion. The laboratory investigation of all revealed renal tubular acidosis with metabolic acidosis associated with hypokalemia, hyperchloremia and persistently positive urine anion gap without renal failure and the urinary pH of >5.5 indicating distal renal tubular acidosis. The patients were found to be homozygous for the mutation in CA II gene and parents were heterozygous for the same mutation. They were started on potassium chloride and sodium bicarbonate.

Discussion: Carbonic anhydrase II deficiency syndrome is a rare disease that can be missed due to a lack of clinical suspicion. It is important that treatment be introduced at an early stage, and serious complications can be avoided with regular follow up. The corner stone of the management of the disorder is alkali therapy to correct the condition, allowing normal growth and decreased stone formation and potassium loss.