Dear friend, welcome to HCM.
sickeling can sometime cause cause painful bony pain crises and sequestration crises. could be spleen
infarcts if there is massive sequestration. should do blood smear exam to see for sickling, haemolysis, usg for spleen etc.
well, there can be other differentials. low chloride could be secondary to vomittings.
pl. consult your doc to check out the same.
take care and pl. keep me posted on your progress.