A third study showed that bone marrow stromal cells from MM patients produced HB-EGF and expressed high mRNA levels of all the ErbB receptor tyrosine kinases except for HER4, while primary MM plasma cells did not express the HBEGF gene but did express variable levels of EGFR (HER1) mRNA and HER4 mRNA [16]. The gene discussed is ERBB4; the disease is Miyoshi myopathy.