Response of Severe Osteomalacia to High Dose Vitamin D3 Replacement in a Patient With Ulcerative Colitis and Liver Transplantation on Immunosuppressive Therapy

Background: Bone disease is common in inflammatory bowel disease (IBD), more frequently in Crohn’s disease than ulcerative colitis (UC). We present the case of a patient with prior history of ulcerative colitis with severe 25 OH vitamin D deficiency and metabolic bone disease. Case: 67 year old male with h/o ulcerative colitis, colon cancer s/p proctocolectomy and ileostomy, chemo-radiation, h/o primary sclerosing cholangitis (PSC) and orthotopic liver transplantation (OLT) 20 years prior presented with presented with severe muscle aches, severe limitation in mobility and severe vitamin D deficiency. He had been on chronic prednisone and tacrolimus, mycophenolate. Three years after OLT, he had fragility fractures at different times in both hips requiring hip arthroplasty. Labs were significant for persistently elevated alkaline phosphatase (ALP) up to 1569 U/L for last 10 years, bone specific ALP at 423.6 mcg/L, Calcium 9 mg/dl, phosphorus 2 mg/dl, 25 OH vitamin D was 4 ng/ml, 1, 25-hydroxy vitamin D (25-OHD) was 34 ng/ml, PTH was 189 pg/ml, urine calcium/creatinine ratio was 50 mg/g and urine NTX at 223 nM BCE/mM. Celiac screen was negative and tacrolimus levels were within normal range. Patient had extensive workup by gastroenterology for elevated ALP including three liver biopsies which were unrevealing. A bone scan showed increased uptake in thoracic region and metaphyses of large joints. A diagnosis of osteomalacia and secondary hyperparathyroidism was made and he was started on high dose vitamin D gradually increased to 8000 units thrice a day. Within few weeks, he noted marked improvement in mobility, bone pain and need for pain medications. In few months, BSAP decreased to 144.9 mcg/l, NTX and PTH also improved. 25 OH has also increased slightly to 13. He continues on high dose vitamin D and 1200mg of calcium daily. Discussion: Our patient likely had severe osteomalacia due to prolonged vitamin D deficiency, caused by multiple etiologies. Firstly, poor absorption in UC might lower 25-OHD levels. Secondly CYP3A enzymes are involved in the metabolism of calcineurin inhibitor tacrolimus as well as vitamin D, this could result in enhanced vitamin D metabolism, which would explain persistently low vitamin D level despite replacement with such high doses. The significant improvement in his symptoms with supplementation resulting in increased mobility despite not having a normal vitamin D level suggest other pleiotropic effects of vitamin D on muscle and bone as well. Additionally effects of liver transplantation on vitamin D metabolism need to be explored further.