This 2-year old female was in her usual state of 
good health until one month prior, when she began 
complaining of generalized abdominal pain.  The "pain 
spasms" occurred every 15-20 minutes, which would 
cause her to "double over"; the pain would then 
gradually subside.  At that time, she was seen in the 
emergency department, where abdominal radiographs 
revealed moderate gas throughout the bowel and a 
stool-filled colon.  An enema resulted in the passage of 
large amounts of stool, and the pain seemed to 
improve.  About one week ago (three weeks later), her 
pain became severe again and, at this point, she 
refused to walk.  Her parents noticed that her knees 
would shake when she stood up, and she appeared 
knock-kneed.  For the last 3 days, these episodes have 
intensified, with each episode lasting approximately 5 
minutes and returning every 15-20 minutes.  Her 
temperature ranged from 37.3 to 38.6 degrees.  She 
was noted to be more agitated at night and was unable 
to sleep because of pain.  She also seemed to favor 
her right leg.  There was no nausea, vomiting, diarrhea, 
cough, rhinorrhea or other symptomatology.
     Exam:  VS  T40.3, P160, RR 46, BP 124/65.  She 
appears tired, but otherwise well-developed and 
well-nourished.  She is somewhat irritable but 
cooperative.  She is in the 50th percentile for height, 
weight and head circumference.  HEENT no 
abnormalities detected.  Neck supple without 
adenopathy.  Heart regular without murmurs.  Lungs 
clear.  Abdomen is soft without definite tenderness.  
Bowel sounds are active.  No rebound.  No 
organomegaly.  No hernias.  Small 1 cm lymph nodes 
are palpable in both inguinal regions.  There is 
tenderness to palpation in the right hip area.  Range of 
motion about this hip is good; however, she fusses 
when this is done.  There does not appear to be any 
pain with palpation of the pubis, and she is able to log 
roll normally.  There are no other bony or joint 
abnormalities noted.
     Initial labs revealed a white count of 21,700 with 
60% neutrophils, 6% bands, 25% lymphs, 8% monos, 
and 1% eos.  Hgb 12.3, Hct 37.2.  Platelet count 
295,000.  Her ESR is 42.  Chemistry panel shows a 
slightly increased LDH at 382 and slightly increased 
alkaline phosphatase at 212.  Radiographs of the 
abdomen and pelvis are ordered.

View abdominal flat plate.


View pelvic radiographs.


     A previous abdominal series done one month ago 
showed a lot of stool.  The overall abdominal gas 
pattern is non-specific and largely unchanged from the 
previous radiographs one month ago.
     The radiograph of the pelvis appears fairly normal at 
first glance.  Examine the bones carefully to see if you 
can detect any abnormalities.



     This pelvis shows cortical thickening and sclerosis of 
the right superior pubic ramus.  Compare the right and 
the left sides.  You can see that the right superior pubic 
ramus is hyperdense and irregular.  This finding can 
also be appreciated in retrospect on the abdominal film 
as well.  The radiologist feels that this could be 
secondary to a low-grade infection, the healing phase of 
histiocytosis, or a malignancy.  
     A CT scan of the abdomen showed no other 
abnormalities.  It confirmed the slight cortical sclerosis 
and thickening of the right superior pubic ramus seen 
on the plain radiographs.
     A radionuclide bone scan was ordered.

View bone scan.

     There is intense uptake in the right superior pubic 
ramus.  The differential includes malignancy versus 
infection.  The L1 vertebral body is abnormal in that the 
left lateral aspect of it appears to be "cold".
     In the operating room, an open biopsy was sent 
for histology and culture.  A frozen section of curettings 
was read as "possible tumor".  The cultures returned 
negative and the final histology was read as chronic 
inflammation and fibrosis.
     She was continued on antibiotics for suspected 
osteomyelitis.  However, she did not improve and her 
fever worsened.  A bone marrow aspiration was 
performed which showed an unusual type of acute 
leukemia.

Discussion
     Skeletal changes that occur in leukemia are due to 
infiltration of the bone by proliferating white cells.  
Characteristically, zones of rarefaction with 
subperiosteal new bone formation in the metaphyseal 
region of the humerus or femur, or in the pelvis or 
spine, are also seen.  Occasionally, there is a 
widespread, diffuse rarefaction of the skeleton (1).
     Lucent metaphyseal bands are said to be 
characteristic of leukemia; however, Rogalsky, et al (3) 
found lytic lesions in 19%, sclerotic lesions in 4%, and 
periosteal new bone formation in 2%.
     In the younger child, an irregular lytic lesion and/or 
the presence of periosteal new bone, with or without a 
lytic lesion, should always suggest osteomyelitis, 
metastatic neuroblastoma, and eosinophilic granuloma, 
along with leukemia (6).  In the older child and 
adolescent, various forms of subacute osteomyelitis 
most often mimic tumors (6).
     Osteomyelitis is an inflammation of the bone.  
Petrola and Vahvanem (5) consider the diagnosis 
established when 2 of the 4 following criteria are 
present:  1) Pus aspirated from bone; 2) Positive bone 
or blood culture; 3) Classic symptoms of localized pain, 
swelling, warmth, and limited range of motion of the 
adjacent joint; and 4) Radiographic changes 
characteristic of osteomyelitis.
     When these criteria are not met, it is helpful to 
remember those conditions that may mimic 
osteomyelitis and therefore be mistaken for such (6).
     Trauma may be the most common.  It shares some 
clinical features with osteomyelitis, including pain, 
tenderness, swelling, and soft tissue swelling on 
radiographs.  Trauma pain improves with time, whereas 
osteomyelitis worsens.  Another differentiating feature 
is the ESR, which is elevated with osteomyelitis, but 
normal with trauma.  
     Neoplasms may mimic osteomyelitis.  Leukemia is 
the most common malignancy in childhood, with bone 
pain being the presenting sign in about 30% (2).  Other 
non-specific symptoms, such as fever, lethargy, and an 
elevated ESR and WBC are often present as well.  
When considering leukemia, other signs and symptoms 
must be aggressively sought:  bone pain in multiple 
sites, easy bruising, bleeding, a low white blood cell 
count, anemia, thrombocytopenia, etc.

References:
     1.  Outline of Orthopedics, 11th ed., John Crawford 
Adams David L. Hamblem, Churchill Livingston, 1990, 
p. 91.
     2.  Hamm IM, Guppa S, Palmer MK, et al.  The 
prognostic significance of radiological and symptomatic 
bone involvement in childhood acute lymphoblastic 
leukemia.  Med Pediatr Oncol 1979;6:51.
     3.  Rogalsky RJ, Black GB, Reed MH.  Orthopedic 
manifestations of leukemia in children.  J Bone Joint 
Surg (Am) 1986;68:494.
     4.  Clausen N, Gortz H, Petersen A, et al.  Skeletal 
scintigraphy and radiography at onset of acute 
lymphoblastic leukemia in children.  Med Pediatr Oncol 
1983;11:291.
     5.  Ptrola H, Vahvanen V.  A comparative study of 
osteomyelitis and purulent arthritis with special 
reference to etiology and recovery.  Infection 
1984;12:55.
     6.  Morrissy RT.  Bone and Joint Sepsis.  In:  
Morrissy RT, Weistein SL (eds).  Lovell and Winters 
Pediatric Orthopedics, 4th ed.  Lippincott-Raven 
Publishers, 1996, pp. 579-619.