Congenital fiber-type disproportion is a rare condition, histologically characterized by a relative type 1 fiber hypotrophy. The main clinical feature is mild-to-severe muscle weakness. In this report, we present the case of a 21-year-old patient with congenital fiber-type disproportion in an outpatient rehabilitative setting to evaluate the feasibility and results of an assessment battery, including bioimpedance analysis (BIA), dynamometry, 3D gait analysis, 6‑min walk test (6MWT), and the timed up and go test (TUG). The patient had a notable decrease in all functional scores. BIA: lean body mass, 38.4 kg (50.2 ± 5.3), body fat, 1.6% (12.4 ± 4.4); hand dynamometry: 18.5 kg left/20.0 kg right (44.8 ± 6.6); walking speed, 58 cm/s (122.7 ± 11.1), step length, 43.0 cm (61.6 ± 3.5); 6MWT: 478.5 m (638 ± 44); TUG: 9.4 s (8.1 ± 1.0). No adverse events were reported. The tests used were easily applicable in clinical routine and well tolerated by our patient.