Abstract
The case of a 60-year-old woman who presented with marked dysgeusia to all food and symptomatic syndrome of inappropriate antidiuretic hormone secretion (SIADH) is described. She eventually turned out to have metastatic small cell lung cancer. The case study explores the interesting constellation of dysgeusia, SIADH and lung cancer.
BACKGROUND
We were surprised to discover a metastatic small cell cancer that was not suspected at the time of presentation. In retrospect it turned out that the triad of dysgeusia, hyponatraemia and lung cancer is unique and incredibly similar triads have been described in past. Dysgeusia is not a non-specific symptom as it is normally perceived, and the unusual triad itself is thought provoking as it raises questions about the underlying mechanism of the syndrome.
CASE PRESENTATION
A 60-year-old, 30 pack-year smoker, Caucasian woman was brought to the emergency department with an acute onset, fluctuating, “confusional” state. She reported a 10-day history of altered taste sensation, loss of appetite and a recent 4.5 kg weight loss. She seemed most concerned with her altered taste and described it as an unpleasant “tin foil-like” taste sensation to all foods. At presentation, she was afebrile, haemodynamically stable and had unremarkable physical examination.
INVESTIGATIONS
Chest x ray was normal and laboratory work showed severe hyponatraemia (111 mmol/litre) with normal serum urea and creatinine levels. In view of euvolaemia, normal thyroid and adrenal functions and urine osmolality of 244 mosm/kg H2O, a diagnosis of SIADH was considered. Her serum osmolality was 213 mosm/kg and spot urine sodium was 44 mmol/litre.
TREATMENT
After initial correction of serum sodium to 122 mmol/litre, the patient’s taste sensation reverted to normal. Subjective dysgeusia relapsed the following day with the relapse of hyponatraemia (116 mmol/litre). She was treated again with 3% normal saline for her unexplained and persistent symptomatic hyponatraemia while possible underlying pathologies were considered.
OUTCOME AND FOLLOW-UP
Imaging work-up revealed a right lung hilar soft tissue mass (fig 1) with cervical node, adrenal and diffuse brain metastases (fig 2) consistent with metastatic cancer. Cytology of the involved cervical node confirmed metastatic small cell cancer. The patient is symptomatically better and receiving chemoradiation.
Figure 1.
CT scan of chest shows (arrow) right hilar mass encasing right main stem bronchus.
Figure 2.
MRI with contrast of brain showed multiple cerebral and cerebellar metastatic lesions with surrounding oedema (arrow points to one such lesion).
DISCUSSION
Dysgeusia is an uncommon symptom of systemic disease and has been associated with a variety of disorders, including malignancies, respiratory infections, micronutrient deficiency, toxins and drugs. Dysgeusia is rarely seen with SIADH1 and our report highlights the remarkable association of unpleasant taste with SIADH as an indicator of lung malignancy. A Medline literature search of English language articles revealed nine individual reports of similar presentations.2–4 All cases presenting with dysgeusia and hyponatraemia were found to have SIADH and lung malignancy, with the small cell predominating (45%). The taste sensation characteristically improved with correction of sodium and relapsed most with the relapse of hyponatraemia. Of note, all cases demonstrated an increased acuity (lowered taste threshold) to all types of food, particularly sweet ones. Dysgeusias commonly seen with non-lung malignancies manifest as loss of taste (increased threshold) and SIADH is not seen. This particular triad of taste perversion, SIADH and lung cancer appears to be unique. It is hypothesised that a humoral entity specific to lung malignancies may affect the G protein-coupled taste receptors and cause altered taste threshold at low serum sodium levels.2 A candidate entity is miraculin: a glycoprotein extracted from West African berries of Richadella dulcifera that alters the configuration of taste receptors and modifies taste.
LEARNING POINTS
Dysgeusia can be the clinical marker of underlying malignancy.
Dysgeusia along with SIADH is almost always associated with lung cancer.
The triad of dysgeusia, SIADH and lung cancer is unique and the physiological basis remains to be elucidated.
Footnotes
Competing interests: None.
Patient consent: Patient/guardian consent was obtained for publication.
REFERENCES
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