Discussion and Conclusion
Thigh swelling is a clinical sign of various infectious or noninfectious
underlying causes. Regarding the patients’ physical examination cold
abscess was the most probable diagnosis since patients did not have
considerable warmness, erythema, and other signs of inflammation at
presentation. Mycobacterial infection is the most common cause of cold
abscess (6), so acid-fast staining was done along with routine culture
and was positive. Furthermore, a PCR test was done for confirmation of
diagnosis which was positive for Mycobacterium Bovis.
BCG is derived from live attenuated Mycobacterium Bovis and according to
the expanded program of immunization (EPI) in Iran, all children receive
BCG vaccination after birth (8). BCG is routinely injected intradermally
over the deltoid muscle. The abscess location in all patients was in the
anterior thigh muscle, the exact site of vitamin K and Hepatitis B
vaccine injection at birth. The positive PCR test for BCG Mycobacterium
Bovis and the abscess location raised the possibility of erroneous
injection of BCG vaccine into the infants’ thigh muscle. We checked the
hospitals where case 2 and case 3 were born and found out that vitamin K
is injected by the midwife after that, BCG and hepatitis B vaccine is
injected by the vaccinator so the most probable situation is the
injection of 0.5 ml of BCG intramuscularly to the left thigh instead of
hepatitis B vaccine (Hepatitis B vaccine is routinely injected to the
left thigh). In case 1, regarding the presence of swelling in the right
thigh, probably 0.5 ml of BCG is injected intramuscularly instead of
vitamin K at birth (vitamin K is routinely injected to the right thigh).
The injection of a high dosage of BCG, 0.5 cc instead of 0.05 ml, and
intramuscular injection instead of intradermal are both factors for
BCG-related abscess which is observed in these cases. Similar cases of
BCG-induced cold abscesses are reported in Saudi Arabia and India. Verma
et al. reported a four-month-old girl from India. The patient presented
with a swelling on the anterolateral side of her left thigh since
receiving an intramuscular Diphtheria, whole-cell Pertussis, and Tetanus
(DwPT) vaccine injection at the age of six weeks. Fine needle aspiration
of the lesion showed caseating granuloma and staining for acid-fast
bacilli was positive. The most probable cause of the abscess, in this
case, is thought to be following erroneous BCG injection instead of DwPT
vaccine, and the diagnosis is not confirmed since the PCR test for BCG
Mycobacterium Bovis was not done. This type of error is not considered
for our cases because the BCG vaccine is not available in vaccination
centers in Iran and the error can only occur in hospital settings while
vaccine injection at birth. The article has mentioned that the swelling
was completely healed in six months without any anti-mycobacterial
therapy. But, we preferred to start treatment to speed up healing and to
prevent further complications (9). Also, Namshan et al. reported five
similar cases of BCG-induced cold abscess from Saudi Arabia. They did
not perform a PCR test for BCG Mycobacterium Bovis and the diagnosis was
based on culture results. Three cases received anti-mycobacterial drugs
and finally, all cases were healed without remarkable problems during a
two-year follow-up (6). The most extensive report is from Saudi Arabia
with 25 cases of BCG-induced abscess as a result of technical errors
during vaccine injection. The diagnosis was based on a positive smear
for acid-fast bacilli for all cases and a positive culture for 17 cases.
Nowadays, PCR test can detect the exact organism and help us for an
accurate diagnosis. In the later study the exact source and route of
infection was unknown but we tried to find where the error originates
from (10). Our recommendation to prevent this error is to assign
separated staff to inject each of the vaccines, injection of BCG and
hepatitis B vaccine in different rooms, and checking the vaccine
injection by a second observer. Also, WHO has warned that the correct
and precise BCG vaccine injection technique by trained staff is
important for optimal efficacy and safety of the vaccine (1).