Could Mononucleosis diagnosis be......

.....masking leukemia symptoms?

I'll try to relay all the info I have as briefly and as comprehensively as possible. 

My 15 year old son has been ill for two weeks. Though several strep and one mono spot test came back negative, the ER doctor feels confident that my son has mono. 

Symptoms are:

Fever

Rash

Swollen/tender lymph nodes

Swollen spleen

Some nausea and vomiting

Unable to eat - which probably explains his slight weight loss - 5lbs or so.

I guess my primary reason to peripherally doubt the mono diagnosis is the rash. At this point, it's all over his face - almost a sunburned appearance. His hands and wrists get welts, but only at night (weird, I know). Though the fever didn't break for 8 days (we're now at day 11), it still comes and goes.

If it helps anyone to know, his bloodwork included platelet values as follows:

1st: 101,000

2nd: 80,000 (2 days after first count)

3rd: 90,000 (2 days after second count)

His WBC was around 3.7 first time, 4.3 the second (I don't recall the value during the 3rd test and I wasn't given a printout.)

Hemoglobin was 14.4 first time,13.8 second time

Hemacrit was 41.4 first time, 40,1 second time.

Monocytes were 17.7 the first time, 12 the second time.

If you're still reading this post, thank you so much. If you're able to shed some light on any of this - even if only to tell me not to get so hung up on the numbers - then thank you yet again.

its hard to diagnose over the internet but I also think this sounds most like mono given the data you've posted.  The mono spot could be negative and he could still have mono.  Ask about the EBV antibody test.  All his symptoms could be explained by mono, including the rash.  His bloodwork does not look like typical leukemia.  Yes the PLT's are a little low but not horrible.  Really the same could be said for the WBC and HG.  A little off but not what is typically seen in leukemia. 

Thank you so much for the reply. You seem quite knowledgeable and I trust your instinct.

We'll be getting some more bloodwork results today. I believe everything points to mono, but leukemia (and meningitis) were mentioned as possibilites.

I'll update if anything comes back screwy or non-mono-ish.

Thanks again!