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Cases have been reported around the world, including in Denmark, the USA, and Korea. There is no apparent gender predominance.

Disease onset can occur at any age (from the neonatal period to adulthood) but symptoms generally start within the first decade of life. The clinical signs are mainly those of non-surgical hypoparathyroidism with hypocalcemia, causing myopathy, muscular weakness, cramps, tetany, lenticular cataracts, and teeth anomalies.

Possible mechanisms causing FHI include: 1) an inappropriate low calcium set-point due to variants in the CASR gene, causing autosomal dominant hypocalcemia; 2) recessive loss of function or dominant negative variants in the GCM2 gene (6p24.22), which encodes a transcription factor of importance to development, proliferation and maintenance of the parathyroid cells; 3) dominant or recessive variants in the PTH gene (11p15.3) causing either impaired secretion of PTH, apoptosis of parathyroid cells, or secretion of bioinactive PTH, with either undetectable or elevated serum levels of immunoreactive PTH, 4) variants in the autoimmune regulator (AIRE) gene without signs of other diseases associated with loss of AIRE function

Diagnosis is based on biochemistry showing low serum calcium and PTH levels, and confirmed by genetic testing. If PTH levels are high, the bioactivity of the PTH molecule may have to be evaluated.

The differential diagnosis includes other non-surgical hypoparathyroidism with hypocalcemia and low PTH levels such as autoimmune hypoparathyroidism, and autoimmune polyendocrinopathy type 1, or syndromes with hypoparathyroidism as a feature like 22q11.2 deletion syndrome. In patients presenting with hypocalcemia with high PTH levels, pseudohypoparathyroidism or secondary hyperparathyroidism should be considered.

Antenatal diagnosis is possible if the genetic variant is known in the family.

Isolated hypoparathyroidism may be sporadic or familial, with autosomal dominant or recessive inheritance.

Management consists of symptomatic treatment with supplementary calcium and active vitamin D.

If well treated, life expectancy is normal but quality of life may be negatively impacted.