Correspondence

Pseudohyponatremia in Multiple Myeloma

Prithvi Giri*, Jacob George*, AK Gupta**, R Gupta***

*Resident Doctor, Department of Medicine, J.L.N. Medical College, Ajmer; **Professor, Department of Medicine, J.L.N. Medical College, Ajmer; ***MGMC, Jaipur. Received: 06.07.2009; Accepted: 23.07.2009

Sir,

Pseudohyponatremia is a clinical condition characterized by an increased fraction of protein or lipid in plasma thereby resulting in an artificially low plasma sodium concentration.1

A 67 years old male patient, known case of multiple myeloma already on chemotherapy was presented with complains of bone pain and generalized fatigue. On examination patient was anemic and hepatosplenomegaly was present. Investigation revealed: Hb 8.0 gm/dl, ESR 120mm/1st hrs. serum albumin 3.28 mg/dl, serum globulin 3.6 gm/dl, Serum Na+ 102 meq/L, serum was viscous, no creamy layer was present. X-ray skull showed multiple punch out lesions, serum electrophoresis – M component 3.2gm/dl. Bone marrow showed plasma cells >20%. Other investigations: TLC, DLC, blood sugar, blood urea, serum creatinine, serum lipid profile, serum K+, serum Ca++, Serum phosphate, CT, BT, PT-INR, ECG, X-ray chest, urine complete examination all were normal.

As the patient was a known case of multiple myeloma without any symptoms of hyponatermia despite severely decreased serum sodium concentration, without having creamy serum (no chylomicronemia) the possibility was considered of pseudohyponatermia, patient was not given any specific therapy for hyponatremia. Differential diagnosis include Chylomicronemia – in which serum is creamy, Paraproteinemia – in which increase serum viscosity and increased plasma osmolality - like hyperglycemia and mannitol.2

Hyponatremia in an asymptomatic patient demands careful evaluation before institution of therapy. In addition the presence of normal serum sodium level in a patient with multiple myeloma should alert the clinician to the possibility that hypernatremia and hypertonicity may be present.3

References

1. Fukagawa M, Kurokawa K, Papadakis MA, Fluid & Electrolyte disorders. International edition of current medical diagnosis and treatment. Editors Mcphee SJ, Papadakis MA, McGraw Hill Publication, New York 2008;758-763.
2. Singer GG, Brenner BM, Fluid and Electrolyte disturbances. Harrison’s Principle of Internal Medicine. Editors Fauci AS, Braunwald E, Kasper DL, Hauser SC Longo DL et al. McGraw Hill Publication, New York 2008;17:274-284.
3. Munshi NC, Longo DL Anderson KC, Plasma cell disorders. Harrison’s Principle of Internal Medicine. Editors Fauci AS, Braunwald E, Kasper DL, Hauser SC Longo DL et al. McGraw Hill Publication, New York 2008;17:700-707.