asthma, disease of the bowels
瘕 centers on chronic internal illness, specifically respiratory difficulty (asthma) and intestinal disease. The two given meanings are distinct medical conditions without a single unifying concept beyond being internal ailments.
瘕 combines 疒 (sickness) with 叚, which likely contributes a phonetic role. The exact historical development of the inner component is uncertain.
The sickness enclosure 疒 wraps around 叚, a shape that looks like a person doubled over with internal distress. Picture chronic asthma tightening the chest and bowel disease cramping the gut inside this enclosure.
For カ, imagine a car (カ) filled with coughing, wheezing passengers—the car's interior becomes a sickroom for asthma and bowel troubles.