Bone Abstracts

Background: Congenital hypoparathyroidism in children is a condition with diverse genetic etiologies. Kenny-Caffey syndrome (KCS) is a rare genetic disorder characterized by hypoparathyroidism, short stature, cortical thickening and medullary stenosis of the tubular bone and dysmorphic features including micrognathia, prominent forehead and eye abnormalities. The autosomal dominant form of KCS [KCS type 2(KCS2)] is differenced from autosomal recessive form of KCS [KCS type 1 (KCS1)] which is caused by mutation of tubulin-folding cofactor E (TBCE) gene, by the absence of intellectual disability. Presenting problem. A 6-year-old boy was born 2,850 gm at 40 weeks of gestation to nonconsanguineous Thai parents. At 1 month of age, he was referred to pediatric endocrinologist because of recurrent generalized convulsion due to hypocalcemia. At this time, his serum Ca, P, Mg, intact PTH levels were 4.3, 8.8, 1.34 mg/dl and 5.5 pg/ml, respectively. Calcium and oral calcitriol administration were started on the basic of diagnosis of primary hypoparathyroidism. At 5 years his height, weight and head circumference were 89.2 cm (−4.4 S.D.), 13.3 kg (−2.5 S.D.) and 48.1 cm (−2.2 S.D.), respectively. He had normal intelligence for his age. Bone survey was done in this case showed medullary stenosis and cortical thickening. He was diagnosed with KCS2 based on clinical finding of hypoparathyroidism, proportionate short stature, and medullary stenosis revealed by radiography.

Clinical management: We obtained peripheral blood sample from this patient with inform consent of DNA analysis. A novel heterozygous missense pathogenic variant c.1670C>G (p.Ala557Gly), chr11:58920811) in the FAM111A gene was identified in the patient. Pathogenic variant in this gene is known to cause Kenny-Caffey syndrome type 2. His parents do not have this variant.

Discussion: In the present study, we identified novel mutation of FAM111A as the gene responsible for KCS2 by applying an exome sequencing strategy. FAM111A constitutively expressed in parathyroid gland and bone may have a role affecting parathyroid gland development and intracellular pathways regulating normal skeletal development and height gain.

Disclosure: The authors declared no competing interests.