Disease burden and treatment sequence of polymyositis and dermatomyositis patients in Japan: a real-world evidence study

INTRODUCTION/OBJECTIVES

Since new consensus on polymyositis (PM) and dermatomyositis (DM) were released in Japan, an updated evidence on treatment landscape and PM/DM burden was essential. This study evaluates treatment burden and overall treatment cost of PM/DM-related inpatient and outpatient visits, treatments, and procedures/patient/year.

METHOD

This retrospective, observational study analyzed insurance claims from Japan Medical Data Center (JMDC) database. Patients with at least one PM/DM diagnosis/one dispensation of treatment between 1 January 2009 and 31 December 2019 were enrolled. Patient characteristics, treatment patterns and sequence, treatment choices, healthcare resource utilization (HCRU), and related costs were assessed. Chi-square test and linear regression model were used to assess impact of patient characteristics on treatment choice.

RESULTS

Patients (836/4,961) receiving a relevant treatment were analyzed. Heart disease (35%), interstitial lung disease (27%), and diabetes mellitus (26%) were frequently identified as comorbidities. Concomitant dispensation of immunosuppressants and systemic steroids was largely found in first and second line of treatment (LoT) while systemic steroids remained as single dominant treatment across all LoTs. HCRU was very low for inpatient visits (0.68 [1.43]) or rehabilitation (4.74 [14.57]). The mean (SD) number of inpatient visits decreased from first (1.23 [2.32]) to third year (0.11 [0.54]). Total mean (SD) healthcare cost per patients per year was ¥ 3,815,912 (7,412,241), with overall drug dispensation compounding to 80% of total cost.

CONCLUSIONS

High concomitant immunosuppressant and systemic steroid prescriptions in first LoT recommend early optimal treatment to manage PM/DM. Although inpatient costs are low, outpatient dispensation costs increase overall economic burden.

Limb-girdle muscular dystrophy type 2B misdiagnosed as polymyositis at the early stage: Case report and literature review

RATIONALE

Dysferlin myopathy is an autosomal recessive hereditary muscular dystrophy due to deficiency of dysferlin caused by alteration of the DYSF gene; Limb-girdle muscular dystrophy type 2B (LGMD2B) is the most common in Its clinical phenotypes. However, LGMD2B is rarely seen in clinical cases and may initially present as weakness of proximalpelvis muscles and muscles in the posterior compartments of thighs,which will then cause difficulty in running and limping during walking. Laboratory tests at an early stage of the disease often indicate an increased level of serum creatine kinase (CK). Moreover, polymyositis (PM) is manifested as symmetrical proximal muscle weakness of the four limbs, accompanied by an increased level of serum CK. Thus, both are very difficult to identify in clinical practice.

PATIENT CONCERNS

A 25-year-old woman was admitted to our department as the limb weakness progressively worsened. She began to experience proximal muscle weakness of both lower limbs without obvious inducement, which markedly increased when she climbed the stairs or stood up after squatting. Then her symptoms worsened, with difficulty in proximal and distal lifting of the lower extremities.

DIAGNOSES

Through combined immunohistochemistry and Western-blot analysis, The patient was diagnosed with LGMD2B.

INTERVENTIONS

There were symptomatic treatments such as coenzyme Q10.

OUTCOMES

After symptomatic treatments, the patient's symptoms were obviously relieved, and the CK level decreased.

LESSONS

Through this case, we found that combined application of immunohistochemistry and Western-blot analysis is helpful in early diagnosis of LGMD2B, and a new site of frame-shift mutation in the patient's DYSF gene was found.