Influence of Dermocorticoids on Bone Mineral Density in Patients With Bullous Pemphigoid

Glucocorticoids have direct effects on bone remodeling by suppressing bone formation (inhibition of osteoblastic differentiation, inhibition of mature osteoblasts function and apoptosis of mature osteoblasts) and by increasing bone resorption (decrease in osteoclast apoptosis and stimulation of osteoclastogenesis). They also have indirect bone effects by decreasing the intestinal absorption of calcium and increasing its urinary excretion, and by inhibiting the somatotropic and gonadotropic axis. This pathophysiology results in excessive bone fragility. Bone loss and increased incidence of fractures occur within 6 months after the introduction of oral corticosteroid therapy, with a partially reversible phenomenon within months of discontinuation. The extent of bone loss depends on the dose and duration of glucocorticoid administration.

The systemic transition of topical corticosteroids depends on several parameters such as excipients, anatomical location, cutaneous state, the dose used and the duration of exposure.

Clobetasol propionate, used for long-term use in bullous pemphigoid, is a Class IV dermocorticoid (highly potent). Patients with bullous pemphigoid will benefit from bone densitometry at the initiation of treatment, at 3 months (theoretical end of the treatment of attack) and at 6 months (theoretical end of the treatment).

Patients will also benefit a blood test of serum calcium, phosphoremia, albumin, 25 OH vitamin D and cortisol at 8 to highlight possible correlations between changes in bone mineral density and phosphocalcic parameters and 8 cortisolemia (braking of the hypothalamic-pituitary-adrenal axis).

Patients will also benefit from standard radiographs of the thoracic and lumbar spine at the initiation of treatment and at 6 months. Follow-up is planned over 6 months, with 2 follow-up visits at 3 months and 6 months.

Inclusion criteria

• Patients aged ≥ 18 years
• Patients with newly diagnosed bullous pemphigoid (BP), treated according to the national diagnostic and care protocol issued by the French Reference Center for Autoimmune Bullous Diseases in April 2016.
• In patients for whom lumbar spine bone densitometry cannot be interpreted at several vertebral levels from L1 to L4 (severe lumbar osteoarthritis, history of lumbar vertebroplasty, osteosynthesis hardware), the data will be interpreted using the remaining evaluable vertebrae. If the BMD of none of the vertebrae from L1 to L4 is evaluable, only hip BMD will be interpreted.
• Patients, or their legal representative, who have received written and oral information and have signed an informed consent form.
• Social Security affiliation.

Exclusion criteria

• Patients receiving anti-osteoporotic maintenance treatment (zoledronic acid, risedronate, alendronate, pamidronate, ibandronate, teriparatide, denosumab, raloxifene).
• Patients requiring immediate initiation of anti-osteoporotic maintenance treatment (T-score < -3 SD at at least one site or FRAX® score above the therapeutic intervention threshold).
• Patients presenting with one or more major risk factors for osteoporosis:

In men and premenopausal women: newly diagnosed or radiologically confirmed vertebral fracture without an obvious traumatic or tumor-related context; personal history of a peripheral fracture occurring without major trauma; systemic corticosteroid therapy prescribed for at least three consecutive months at a dose ≥ 7.5 mg/day prednisone equivalent; prolonged hypogonadism; untreated active hyperthyroidism; hypercortisolism; primary hyperparathyroidism; and osteogenesis imperfecta.

• In postmenopausal women: premature menopause < 40 years of age; BMI < 19 kg/m²; parental history of femoral neck fracture without major trauma in a first-degree relative; history of corticosteroid therapy for at least three consecutive months at a dose ≥ 7.5 mg/day prednisone equivalent.
• Patients who have received topical corticosteroids for more than one week during the two weeks preceding inclusion.