Severe hypocalcemia is a serious concern in infants born with DiGeorge Syndrome. Patients with hypocalcemia may exhibit Chvostek's sign where tapping of the facial nerve elicits contraction of the facial muscles.
DiGeorge syndrome is one of the 22q11 microdeletion syndromes. Presentation may be variable and include cleft palate, abnormal facies, thymic aplasia leading to T-cell deficiency and recurrent infections, cardiac defects, and hypocalcemia secondary to absence of the parathyroid glands. Patients with hypocalcemia may complain of numbness and tingling around the mouth and in the fingers and toes. Furthermore, tetany may be manifested by hyperactive deep tendon reflexes and positive Chvostek's sign and Trousseau's sign on physical exam. Trousseau's sign refers to the elicitation of carpal spasms when a blood pressure cuff is inflated to a pressure higher than the patient's systolic blood pressure for 3 minutes. On EKG, patients may have a prolonged QT interval.
Solomon and Muenke discuss when to suspect a genetic syndrome. General themes include the discovery of dysmorphic features that are evident on physical examination, multiple anomalies in one patient, unexplained neurocognitive impairment and a family history suggestive of hereditary disease. Other important parts of the history include ethnic background and a history of consanguinity.
Fernandez et al. review 22q11 deletion syndromes. Individuals with DiGeorge and velo-cardio-facial syndromes present with both phenotypic diversity and variable expressivity. The most frequent clinical features are conotruncal congenital heart defects, velopharyngeal insufficiency, hypocalcemia, and carniofacial dysmorphism. Other less frequent duplications and deletions in this region have been reported with milder phenotypes.
Illustration A depicts the classic facial appearance in DiGeorge Syndrome.
Answer 1: Hypercalcemia, not hypocalcemia, is a risk factor for kidney stones.
Answer 2: Patients may have a T-cell deficiency, due to thymic aplasia, but would have normal B-cell counts.
Answer 4: A shortened QT interval would be a sign of hypercalcemia. In hypocalcemia, the QT interval is prolonged.
Answer 5: Patients with hypocalcemia usually exhibit hyperactive instead of hypoactive deep tendon reflexes.
Solomon BD, Muenke M. When to suspect a genetic syndrome. Am Fam Physician. 2012 Nov 1;86(9):826-33.
PMID:23113462 (Link to Abstract)
Fernández L, Nevado J, Santos F, Heine-Suñer D, Martinez-Glez V, García-Miñaur S, Palomo R, Delicado A, Pajares IL, Palomares M, García-Guereta L, Valverde E, Hawkins F, Lapunzina P. A deletion and a duplication in distal 22q11.2 deletion syndrome region. Clinical implications and review. BMC Med Genet. 2009 Jun 2;10:48. doi: 10.1186/1471-2350-10-48.
PMID:19490635 (Link to Abstract)