Clinical and genetic features of Kenny-Caffey syndrome type 2 with multiple electrolyte disturbances: A case report

Abstract

BACKGROUND Hypoparathyroidism, which can be sporadic or a component of an inherited syndrome, is the most common cause of hypocalcemia. If hypocalcemia is accompanied by other electrolyte disturbances, such as hypokalemia and hypomagnesemia, then the cause, such as renal tubular disease, should be carefully identified. CASE SUMMARY An 18-year-old female visited our clinic because of short stature and facial deformities, including typical phenotypes, such as low ear position, depression of the nasal bridge, small hands and feet, and loss of dentition. The lab results suggested normal parathyroid hormone but hypocalcemia. In addition, multiple electrolyte disturbances were found, including hypokalemia, hypocalcemia and hypomagnesemia. The physical signs showed a short fourth metatarsal bone of both feet. The X-ray images showed cortical thickening of long bones and narrowing of the medulla of the lumen. Cranial computed tomography indicated calcification in the bilateral basal ganglia. Finally, the genetic investigation showed a de novo heterogenous mutation of “FAM111A” (c. G1706A:p.R569H). Through a review of previously reported cases, the mutation was found to be the most common mutation site in Kenny-Caffey syndrome type 2 (KCS2) cases reported thus far (16/23, 69.6%). The mutation was slightly more prevalent in females than in males (11/16, 68.8%). Except for hypocalcemia, other clinical manifestations are heterogeneous. CONCLUSION As a rare autosomal dominant genetic disease of hypoparathyroidism, the clinical manifestations of KCS2 are atypical and diverse. This girl presented with short stature, facial deformities and skeletal deformities. The laboratory results revealed hypocalcemia as the main electrolyte disturbance. Even though her family members showed normal phenotypes, gene detection was performed to find the mutation of the FAM111A gene and confirmed the diagnosis of KCS2.

Further delineation of phenotype and genotype of Kenny–Caffey syndrome type 2 (phenotype and genotype of KCS type 2)

“…In a large group of Chinese patients with childhood‐onset hypoparathyroidism, only one out of 173 patients was reported with KCS2 (Wang et al., 2019 ). Until now, a total of six patients from five papers had been reported in China (Cheng et al., 2021 ; Wang et al., 2019 ; Yuan et al., 2023 ), including a pair of monozygotic twins (Cheng et al., 2021 ). In this study, we recruited eight Chinese individuals with heterozygous pathogenic variants in FAM111A from six families, adding to the phenotypic spectrum of KCS2.…”