Box 1: Relevant serum laboratory values across the patient’s initial and most recent clinic visits over a 10-month period, with hydroxychloroquine started after his second clinic visit*

Laboratory test	Visit no. 1	Visit no. 2	Visit no. 4	Visit no. 5	Visit no. 8	Visit no. 9	Normal range
Ionized calcium, mmol/L^†	1.48	1.54	1.63	1.47	1.26	1.27	1.12–1.32
Calcium, mmol/L^‡	3.04	3.21	3.28	2.87	2.57	2.57	2.20–2.62
Phosphate, mmol/L	0.95	0.94	1.05	0.89	0.78	0.73	0.80–1.40
PTH, ng/L	4.72	2.83	3.77	10.37	–	–	12.26–71.67
1,25 dihydroxyvitamin D₃, pmol/L^§	274	313	234	187	125	102	60–206
25-hydroxyvitamin D₃, nmol/L^§	241	186	152	135	96	108	25–200
Creatinine, μmol/L	372	241	271	237	199	186	64–110
Estimated GFR, mL/min/1.73m²	< 15	25	22	26	32	34 >	60

Note: GFR = glomerular filtration rate, PTH = parathyroid hormone.
* The patient’s third clinic visit was a routine visit to check his response to the hydroxychloroquine. Clinic visits occurred every 4–6 weeks.
↵† Corrected for pH 7.4.
↵‡ Corrected for albumin.
↵§ These results became available 2 weeks after blood was drawn on a clinic visit.