We describe the case of a 62-year-old woman with schizophrenia and intellectual disability, who presented with intermittent muscle cramping for 2 weeks. A dysmorphic face and a positive Trousseau's sign, but without ecchymosis or petechial lesion were noted. Laboratory data revealed impaired renal function (creatinine level = 1.6 mg/dL), severe hypocalcaemia (total calcium level = 5.7 mg/dL) with low urinary calcium excretion (13.2 mg/day), hyperphosphatemia (phosphate level = 7.3 mg/dL), and low intact parathyroid hormone level (52.5 pg/mL)-indicating primary hypoparathyroidism. A blood smear revealed thrombocytopenia (30,000 thrombocytes/µL) and giant platelets-indicating macrothrombocytopenia. Chromosome 22q11.2 deletion syndrome (22q11.2DS) in the deficient chromosome 22 was confirmed using multiplex ligation-dependent probe amplification showing haploinsufficiency in GP1BB and TBX-1. Cooccurrence of hypoparathyroidism and macrothrombocytopenia in 22q11.2DS is rare and can easily be misdiagnosed as idiopathic thrombocytopenia purpura and inappropriate splenectomy or chemotherapy can aggravate hypoparathyroidism. Early diagnosis of 22q11.2DS, characterized by hypoparathyroidism and macrothrombocytopenia, in elderly patients with schizophrenia can facilitate in avoiding circuitous diagnosis and inappropriate management.
Keywords: 22q11.2 deletion syndrome; hypoparathyroidism; macrothrombocytopenia.