Hereditary Spherocytosis

The correct answer is hereditary spherocytosis!

The trick was to derive the MCHC from the Hb and Hct (MCHC = Hb/Hct). This gives a very high value, consistent with ++ hyperchromia.

While there are several causes of hyperchromic RBCs (see graphic), there are really only 2 causes that lead to this degree of MCHC change:

• Spherocytosis – HS (AIHA less commonly)
• Cold agglutinin disease (artifact)

So from just two normal appearing values (Hb and Hct), you can deduce that this patient likely has compensated HA in setting of HS (CAD was not provided as an option in the poll)!