Hi, as you have difficulty in breathing during asthma attack, your abdominal muscles might have been used more than normal.So they thought that it is myositis or may be a simple myalgia. But you are saying that you have a mass in the left abdomen below the rib cage(left hypochondrium). First, you need to evaluate whether it is mobile when you are trying it to move or it is in subcutaneus tissue or from muscle or intra abdominal organ enlargement or may be some other condition. Sometimes the mass may be sebaceus cyst or lipoma which doesn t have any connection to abdominal pain. If it is increasing in size and very painful it can be a liposarcoma, for which you immediately have to consult a surgeon. If there is redness and if it is shining. That can be a liver abscess or sub phrenic(below rib cage) abscess. It can also be a splenic enlargement due to malaria or kalaazar or anaemiaetc., It can also be a splenic flexure of colon ( a carcinoma). It can be cyst( fluid filled bag) orpseudo cyst from pancreas. may adrenal gland tumour or hydronephrosis( kidney disease). It can also be an obstructive hernia or So , please consult a surgeon and get an ultra sound abdomen scanning and other blood and urine investigations.