Atypical presentation of COVID-19 in an older adult: Lethargy and vomiting from severe hypovolemic hyponatremia.

Dear Editor,

The coronavirus disease 2019 (COVID‐19) pandemic disproportionately affects older adults, who suffer from more severe infections and higher mortality rates.1, 2, 3 A total of 75% of known COVID‐19 cases are aged >50 years, and the case fatality rate ranges from 8% to 15% in patients aged >70.4, 5 Importantly, COVID‐19 infections in older adults might present with atypical symptoms, posing a diagnostic challenge. For instance, COVID‐19 can manifest in older patients as delirium or falls, without fever or respiratory symptoms.6, 7 Here, we describe an older patient with COVID‐19 pneumonia who presented with lethargy and vomiting caused by severe hypovolemic hyponatremia.

A 65‐year‐old Malay men presented to the emergency department with acute lethargy for the past 1 week, which he initially attributed to fasting during Ramadan. Over the past 2 days, he felt intermittently nauseous, and vomited small amounts of non‐bloody, non‐bilious gastric contents twice a day while fasting, but he did not have diarrhea or abdominal pain. He denied fever or respiratory symptoms. His family physician found leukopenia in his blood tests and referred him to the emergency department. Before his symptoms started, he was well and working full‐time. His only medication was oral allopurinol 100 mg once a day for gout prophylaxis. Otherwise, he had no significant past medical history or family history. He did not consume supplements, was teetotal and never smoked. On examination, he was afebrile and hemodynamically stable with no supplemental oxygen required, but his oral mucosa was dry. Cardiac, respiratory, abdominal and neurological examinations were normal, and the patient was clinically euthyroid.

Blood investigations showed severe hyponatremia (sodium concentration 115 mmol/L), a raised inflammatory marker (C‐reactive protein 29.5 mg/L) and leukopenia (total leukocytes 1.8 × 109/L). Serum creatinine, urea, potassium and bicarbonate concentrations were unremarkable, and the patient was not anemic or thrombocytopenic. The elevated C‐reactive protein and leukopenia prompted a search for the source of an occult infection, and consequently a chest X‐ray showed patchy airspace opacities in the middle and lower lobes of the right lung indicative of community‐acquired pneumonia. Due to the COVID‐19 outbreak in Singapore, the patient was isolated in the Respiratory Infection Surveillance Ward, and a nasopharyngeal swab was obtained for a SARS‐CoV‐2 reverse transcriptase‐polymerase chain reaction test, which was positive. Conversely, polymerase chain reaction for atypical organisms, such as Mycoplasma, Chlamydophilia and Bordetella, were negative. As the patient had no cough, we could not send sputum for tests (Fig. 1).

Figure 1

The patient's chest radiograph shows patchy airspace opacities in the middle and lower lobes of the right lung.

Further investigations were carried out to determine the cause of the severe hyponatremia. A thyroid function test showed a low thyroid‐stimulating hormone level of 0.221mIU/L, a normal free T4 level of 12.86 pmol/L and an undetectable free T3 level (<2.0mcg/dL). A short tetracosactrin (Synacthen) test carried out at 08.00 hours showed an adequate adrenal response (299 nmol/L at 0 min, 630 nmol/L at 30 min, 834 nmol/L at 60 min). Blood and urine tests were not suggestive of syndrome of inappropriate antidiuretic hormone (serum osmolarity 256 mOsm/kg, urine osmolarity 83 mOsm/kg, urine sodium <20 mmol/mL). The patient was reviewed by an endocrinologist, who diagnosed severe hypovolemic hyponatremia and euthyroid sick syndrome.

Having been diagnosed with mild COVID‐19 pneumonia, the patient was transferred to the COVID‐19 Isolation Ward. The patient was empirically treated with oral amoxicillin 875 mg with clavulanate 125 mg (Augmentin) twice a day and oral doxycycline 100 mg twice a day for 7 days, according to the hospital's antibiotic guidelines for community‐acquired pneumonia. For his severe hypovolemic hyponatremia, the patient was judiciously hydrated with a slow intravenous isotonic saline infusion, and serum sodium concentration increased from 115 to 127 mmol/L over a period of 1 day, and then to 132 mmol/L over a period of 4 days. Subsequently, his lethargy, nausea and vomiting resolved. As the patient remained afebrile and hemodynamically stable, with no supplemental oxygen required, he was not treated with antivirals. On the eighth day of his admission, the patient was discharged to a quarantine facility within the community. None of the healthcare workers who cared for the patient contracted COVID‐19.

To our knowledge, this is the first reported case of a COVID‐19 infection that presented with lethargy and vomiting caused by severe hypovolemic hyponatremia. Notably, SARS‐CoV‐2 binds to angiotensin‐converting enzyme receptors, and is postulated to cause electrolyte imbalances (such as hyponatremia and hypokalemia) by inducing renal excretion of these electrolytes. Furthermore, this case highlights that, particularly in older persons, COVID‐19 infections might have atypical presentations.2, 3 Therefore, as older adults are more susceptible to severe complications of COVID‐19, clinicians should lower their threshold to test for COVID‐19 in acutely ill older patients during COVID‐19 outbreaks. Prompt surveillance and early diagnosis of COVID‐19 are essential to prevent nosocomial transmission of the disease, especially as delayed diagnosis has resulted in the infection of healthcare workers.

Disclosure statement

The authors declare no conflict of interest.