ESPE Abstracts (2016) 86 P-P2-168

A Case of Genetically Proven Carbonic Anhydrase II Deficiency

Zdravka Todorovaa, Elissaveta Stefanovaa,b, Krasimira Kazakovaa,b, Desislava Yordanovaa,b & Ivan Litvinenkoa,b

aUniversity Children’s Hospital, Sofia, Bulgaria; bMedical University, Sofia, Bulgaria

Background: Carbonic anhydrase II (CAII) deficiency is extremely rare (<1:1 000 000) autosomal recessive disease, which is characterized by the triad of osteopetrosis, basal ganglia calcifications and renal tubular acidosis. In addition short stature, facial dysmorfism and different degree of mental retardation are possible features. Different mutations of the gene for CAII on 8q21.2 lead to impaired enzyme activity and typical clinical, biochemical and imaging manifestations.

Objective and hypotheses: A 5-year-old girl, from normal pregnancy of parents, who deny consanguinity was referred to endocrinology department because of short stature, developmental delay and basal ganglia calcifications on CT scan, found incidentally.

Method: Clinical evaluation, laboratory tests of hormones, electrolytes, biochemical indices, acid-base status, infections, kidney ultrasound, radiological examination of bone age, neurologic, ophthalmologic examination and molecular genetic analysis.

Results: Clinical evaluation confirmed mild dysmorphic features, short stature SDSh(−2, 97), low weight, SDSw(−3,0) and some developmental delay. Laboratory testing proved severe decompensated normal anion gap metabolic acidosis, low normal Ca, Ca2+, high P, Cl and blood urea nitrogen, normal values of intact PTH, ACTH, serum Cortisol at 0800 h and 2000 h, TSH, fT4. Imaging studies showed delayed by 2 years bone age and increased bone density, as well as mild nephrocalcinosis. A molecular genetic analysis revealed homozygous mutations c.275A>C, pGln92Pro on the gene for CAII on 8q21.2, which confirmed the clinical diagnosis. This mutation is found only in two other patients of gypsy origin from Czech Republic and Germany. The child receives oral 8,4% Sodium bicarbonate for correction of metabolic acidosis and showed improvement in clinical manifestations and laboratory data.

Conclusion: Children with this rare syndrome may come into medical attention for failure to thrive, short stature, developmental delay or brain calcifications. It is crucial for the patient’s quality of life and long-term prognosis to receive an early diagnosis and efficient treatment, because metabolic compensation provides normal adult height and hematologic and neurologic complications of osteopetrosis are not severe.

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