Background and Objectives
There are few large studies describing the frequency and associations of respiratory complications of facioscapulohumeral muscular dystrophy (FSHD). Using data from the population-based Muscular Dystrophy Surveillance, Tracking, and Research Network (MD STARnet), we examined respiratory testing and clinical disease characteristics in FSHD.
Methods
Individuals with confirmed FSHD during 2008-2016 who received clinical care in a MD STARnet surveillance area (CO/IA/NC/NY/SC/UT) were included. Frequencies and proportions were calculated for selected outpatient respiratory assessments: evaluation by a pulmonologist, respiratory therapist, or sleep specialist (yes/no), and documented pulmonary function testing [PFT (yes/no)], including forced vital capacity (FVC), inspiratory/expiratory pressure (MIP/MEP), and sleep study. We compiled all abnormal test results defined as FVC <80%/<50%/<30% predicted or absolute FVC <1L, MIP <60 cmH2O and MEP <-80 cmH2O, and nocturnal hypoventilation as noted on sleep study. We also recorded respiratory interventions (NIV, O2, tracheostomy). Frequencies were examined relative to disease characteristics (FSHD type, onset age, non-ambulatory status, scoliosis, lordosis), presence/absence of obesity, and length of follow-up in MD STARnet.
Results
Of 170 individuals with FSHD, 25 (14.7%) were evaluated by any respiratory specialist and 34 (20.0%) underwent PFT. FVC<80% predicted (n=22) was recorded for 64.7% of individuals tested; additional respiratory outcomes examined were rare among all individuals (<5%). Sleep studies and any respiratory intervention were infrequent (14.7% each). Frequency of evaluations and documented respiratory insufficiency were higher among those with childhood onset FSHD, scoliosis or lordosis, non-ambulatory status, and >4 years of follow-up.
Discussion
Our observed low rates of respiratory testing among all confirmed cases of FSHD but relatively high rates of mild respiratory insufficiency among those tested may suggest individuals at highest risk of respiratory compromise are receiving testing. Broad implementation of the current FSHD guidelines recommending all individuals receive baseline respiratory evaluation at diagnosis could identify more respiratory insufficiency.