In simple words: This code is used for breathing problems related to another health condition. It's important to also code the main health condition causing the breathing problem.

Respiratory disorders in diseases classified elsewhere. Code first underlying disease, such as: amyloidosis (E85.-), ankylosing spondylitis (M45.-), congenital syphilis (A50.-), cryoglobulinemia (D89.1), early congenital syphilis (A50.0-), plasminogen deficiency (E88.02), schistosomiasis (B65.0-B65.9). Excludes1: respiratory disorders in: amebiasis (A06.5), blastomycosis (B40.0-B40.2), candidiasis (B37.1), coccidioidomycosis (B38.0-B38.2), cystic fibrosis with pulmonary manifestations (E84.0), dermatomyositis (M33.01, M33.11), histoplasmosis (B39.0-B39.2), late syphilis (A52.72, A52.73), polymyositis (M33.21), Sjögren syndrome (M35.02), systemic lupus erythematosus (M32.13), systemic sclerosis (M34.81), Wegener's granulomatosis (M31.30-M31.31)

Example 1: A patient with ankylosing spondylitis (M45.-) experiences shortness of breath and reduced lung capacity. J99 is used as a secondary code to M45.- to specify the respiratory involvement., A patient with amyloidosis (E85.-) develops pleural effusions causing difficulty breathing. J99 is used with E85.- to indicate the respiratory complication., A patient with schistosomiasis (B65.0-B65.9) presents with pulmonary hypertension. J99 is used in conjunction with B65.0-B65.9 to denote the respiratory manifestation of the parasitic infection.

Documentation should clearly link the respiratory issue to the underlying disease. Medical records should specify the type of respiratory disorder, the underlying disease, and any related symptoms.