We report a 55 year old female, who was diagnosed to have chronic autoimmune hypothyroidism for past 5 years on thyroxine, presented with insidious onset of constitutional symptoms for 6 months duration. Her thyroid function tests showed satisfactory control. Despite satisfactory control of thyroid function tests, she experienced a gradual but profound loss of weight of thirty six (36 kg) kilograms with loss of appetite for the same duration. She did not have any past or contact history of tuberculosis or a past history of malignant disease. She is not on any medication too. Over the last few months, she was complaining of a worsening generalized malaise, which affected her activities of daily living. There was no muscle pain but complained that her walking has become clumsy and it was difficult for her to stand from the seated position. On examination, she was cachectic with BMI of 19 kg/m2 and was found to be pale, without icterus or palpable lymph nodes or organomegaly. Neurological examination revealed reduced muscle power in lower limbs with diminished reflexes without any sensory deficit. Her fundoscopic examination was normal.
Her initial investigations revealed normocytic normochromic anaemia (8.9 g/dl) with rouleaux formation. She had elevated ESR of 120 mm/1st hour and hypokalemia (2.9 mmol/l). Liver function tests showed reversed albumin to globulin ratio (Albumin - 29 g/l, Globulin - 50 g/l). On further investigation, serum protein electrophoresis revealed a monoclonal band in the gamma region. However, her skeletal survey and urinary Bence Jones protein were negative. In bone marrow aspiration, there were 15 % clonal plasma cells and immunofixation revealed IgG myeloma.
After confirming the low potassium, we detected her urinary excretion of potassium to be increased. Furthermore, her arterial blood gas showed a marked hyperchloraemic metabolic acidosis (pH 7.2, HCO3- 8.2 mmol/l) with normal anion gap (15 mmol/l). Her urine pH was 7.5 and was high despite systemic acidosis and the fractionated bicarbonate excretion was 3 %. Her non-contrast CT of kidneys revealed bilateral non-obstructing renal calculi (Fig. 1).
Her autoimmune markers namely ANA, Rheumatoid factor, Complement levels were all normal. Her serum ionized calcium level (1.1 mmol/l) and urinary excretion of oxalate, phosphate, uric acid, calcium and citrate levels were within normal range. Contrast CT scan of chest and abdomen did not show evidence of sarcoidosis or malignancy. The summary of the investigations is depicted in Table 1.