Endocrine Abstracts

Case: 60 year old male presented to his GP with symptoms of polydipsia, polyuria, reduced appetite and weight loss of about 1 stone over 6-7 weeks. Routine bloods showed abnormal blood film with left shift in neutrophils, moderate thrombocytopenia (61), basophilia and occasional blasts (1%). Morphology was suggestive of Chronic Myeloid Leukaemia (CML). He was referred to haematology for further management and had specialist bloods and a bone marrow examination. Due to ongoing symptoms of polyuria and polydipsia, repeat bloods were taken - increasing sodium (153 mmol/l), high serum osmolality (320 mmol/kg) and low urine osmolality (171 mmol/l). Review by Endocrine Consultant suggested a clinical diagnosis of AVP deficiency and he was treated with Desmopressin (DDAVP) 100 mg PO nocte. On DDAVP, the sodium rapidly normalised. MRI pituitary showed absent posterior pituitary high signal and a small lesion at the base of the pituitary stalk: differential diagnosis included a proteinaceous or midline inclusion cyst, hamartoma or possibly low-grade glioma. Haematology results confirmed a Philadelphia chromosome with final diagnosis being chronic phase CML, treated with oral Dasatinib (tyrosine kinase inhibitor). From a CML point of view- he had a normal Full Blood Count within 2 months and was in a Major Molecular Remission 4 months after starting Dasatinib. MRI at 3 months showed remission of the hypothalamic enhancing lesion and still showed an absent posterior pituitary bright spot. His Haematology Consultant suggested that the lesion could have been a chloroma related to the CML, which had responded to the Dasatinib treatment. A repeat MRI at 9 months showed normal appearances of the infundibulum, hypothalamus and posterior pituitary bright spot.

Discussion: Chloroma also known as Myeloid sarcoma (MS) is a rare condition characterized by the presence of solitary or multiple tumours consisting of immature myeloid cells, at an extra medullary site. Most commonly, it occurs concurrently with acute myeloid leukaemia, myeloproliferative disorders or myelodysplastic syndrome. Symptoms usually occur as result of mass effect or organ damage.

Conclusion: AVP deficiency secondary to chloroma is very rare (6 case reports in the literature). This case shows an early presentation with AVP deficiency concurrently with the diagnosis of CML, with Dasatinib treatment resulting in resolution of the presumed hypothalamic chloroma and subsequent reappearance of the posterior pituitary bright spot. In this case the principle of ‘Occam’s razor’ resulted in a unifying diagnosis in a patient presenting with two seemingly unrelated rare medical conditions.