Lewis & Short

phthĭsisco, ĕre, v. inch. n. [phthisis], to become consumptive or phthisical: phthisiscentibus medicabilis piscina, Sid. Ep. 5, 14. († phthitărus, i, m., a false read. for phthir (q. v.), Plin. 32, 11, 53, § 150.)