OBJECTIVES: XLMTM, a rare monogenic disease caused by mutations in the MTM1 gene, is characterized by profound muscle weakness, respiratory failure, and early death. This study aimed to quantify the long-term economic burden of XLMTM.

METHODS: This retrospective longitudinal study used the IQVIA PharMetrics Plus^® commercial claims database from January 1, 2006 to September 30, 2018. As there is no XLMTM-specific diagnosis code, study patients were limited to males with 1+ reported diagnostic code(s) used for XLMTM within their first 18 months of life (ICD-9-CM: 359.0 (Congenital hereditary muscular dystrophy) or ICD-10-CM: G71.2 (Congenital myopathies)). Patients also met criteria identified in the RECENSUS study of confirmed XLMTM patients (NCT02231697); those with evidence of spinal muscular atrophy or Duchenne muscular dystrophy were excluded. Outcomes examined were healthcare resource utilization and mean annual per patient costs for private insurers, by age. Limited home-health care costs in commercial claims may underestimate the direct economic burden, especially in stabilized XLMTM patients.

RESULTS: Among 49 patients meeting study criteria, mean age at first observable diagnosis was 4.4mo (SD:5.9). Following diagnosis, patients were observable for 30.94 months, on average [SD:31.38], with hospitalizations that were frequent (mean per patient: 7.29 [SD:7.07]) and lengthy (mean: 123.35 days [SD: 159.15]); nearly three quarters of all patients (73%) had at least 1 NICU stay. All patients eventually required ventilatory support, and most (80%) received tracheostomies. Costs were highest in the first four years of life (ages 0-3y), with mean annual costs of $403,101 per patient, totaling $1,612,405 from birth up to age 4y. Annual costs were lower for patients who survived, declining to $214,949 (ages 4-7y) and $147,948 (ages 8-11y).

CONCLUSIONS: Healthcare resource use is intensive in XLMTM, with costs highest at the beginning of life when life-supportive resource use is highest for acutely ill patients.