When thyroid labs do not add up, physicians should ask patients about biotin supplements.

A 69-year-old woman with a remote history of Graves' disease treated with radioactive iodine ablation, who was maintained on a stable dose of levothyroxine for 15 years, presented with abnormal and fluctuating thyroid function tests which were confusing. After extensive evaluation, no diagnosis could be made, and it became difficult to optimise the levothyroxine dose, until we became aware of the recently recognised biotin-induced lab interference. It was then noticed that her medication list included biotin 10 mg two times per day.

Syndrome of inappropriate antidiuretic hormone associated with eosinophilic granulomatosis and polyangiitis.

A 62-year-old man presented with classic signs and symptoms of eosinophilic granulomatosis and polyangiitis (EGPA, also known as Churg-Strauss syndrome)-mononeuritis multiplex, palpable purpura, hypereosinophilia, positive P-ANCA (perinuclear anti-neutrophil cytoplasmic antibodies) developed diffuse alveolar haemorrhage. The patient had longstanding mild hyponatraemia, but developed moderate and symptomatic hyponatraemia characteristic of the syndrome of inappropriate antidiuretic hormone. The patient's serum sodium returned to his baseline- mildly hyponatraemic, after initiation of treatment targeted towards EGPA.

Epistaxis and gross haematuria with severe thrombocytopaenia associated with influenza vaccination.

Epistaxis may be attributed to many causes during the winter including dry mucous membranes from low indoor humidity from heating. However, epistaxis may also be due to thrombocytopaenia. Immune thrombocytopaenia purpura (ITP) is an autoimmune disorder causing thrombocytopaenia.

One month of nitrous oxide abuse causing acute vitamin B deficiency with severe neuropsychiatric symptoms.

A 21-year-old university student studying abroad in the USA presented to the emergency department with double vision, lower extremity weakness with difficulty ambulating and other neuropsychiatric symptoms. MRI of the brain and spinal cord were normal. Vitamin B was 78 pg/mL (58 pmol/L, reference 211-911 pg/mL).

Lemierre's syndrome and 2016 American College of Physician guidelines for pharyngitis: no to empiric coverage for bacterial pharyngitis. While no role for routine Fusobacterium PCR, keep suspicion for this pathogen.

An 18-year-old woman presented to clinic with acute pharyngitis with 4/4 Centor criteria. Rapid streptococcal antigen test was negative. The patient, who was allergic to penicillin, was prescribed azithromycin.