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[Pseudohypoparathyroidism or hypoparathyroidism? A misleading clinical presentation]
1Unité d'endocrinologie, Département de Médecine de l'adulte, CHU Hôpital Sud, 16, boulevard de Bulgarie, BP 56129, 35056 Rennes Cedex, France.
Annales D'Endocrinologie
|February 15, 2002
Summary
A 22q11 microdeletion diagnosis, initially suspected due to Albright's hereditary osteodystrophy, was confirmed in a hypocalcemic patient. This highlights the importance of genetic testing for 22q11 microdeletion in hypoparathyroidism cases.
Area of Science:
- Genetics
- Endocrinology
- Pediatrics
Background:
- Albright's hereditary osteodystrophy (AHO) and pseudohypoparathyroidism type Ia are common considerations for patients presenting with hypocalcemia and hyperphosphatemia.
- The 22q11.2 deletion syndrome, encompassing DiGeorge syndrome and CATCH 22, is a complex genetic disorder with a wide range of clinical manifestations.
- Hypoparathyroidism is a known complication of 22q11.2 deletion syndrome, often presenting in infancy.
Observation:
- A 27-year-old woman presented with hypocalcemia and hyperphosphatemia during pregnancy, exhibiting features suggestive of AHO.
- Low parathyroid hormone (PTH) levels ruled out pseudohypoparathyroidism type Ia.
- Subsequent genetic testing revealed a 22q11 microdeletion, supported by the affected children's presentation of neonatal hypocalcemia, dysmorphic features, and renal malformations.
Findings:
- The patient's phenotype, initially suggestive of AHO, was ultimately attributed to a 22q11 microdeletion.
- Retrospective analysis identified CATCH 22 (Cardiac defect, Abnormal face, Thymic hypoplasia, Cleft palate, Hypocalcemia) features in the patient, including abnormal facial features, hypernasal voice, developmental delay, and a history of recurrent otitis and idiopathic thrombocytopenic purpura.
- The 22q11 microdeletion was confirmed via Fluorescence In Situ Hybridization (FISH).
Implications:
- The 22q11 microdeletion should be investigated in all patients with unexplained hypoparathyroidism, even without cardiac anomalies.
- Patients with CATCH 22 syndrome may have an increased predisposition to autoimmune diseases due to thymic dysfunction.
- This case underscores the importance of considering genetic testing for 22q11 microdeletion in the differential diagnosis of hypoparathyroidism with overlapping features of other genetic syndromes.