Discussion about differential diagnosis of fever and rashes could be found in review articles and guidelines elsewhere. Nonetheless, neoplastic skin manifestation of hematologic malignancy especially Langerhans cell histiocytosis should always be kept in mind. These manifestations together with hepatosplenomegaly can closely mimic those of hematological malignancies (
16). Our aim for the present report however, was to emphasize on rare manifestation of BCG adverse events in immunocompromised infants with PID. Pediatricians should be mindful of the fact that these complications are not uncommon in immunodeficient patients in our region (
5-
12). Notably, presence of acid fast bacilli within the cytoplasm (intracellularly) is an uncommon yet interesting phenomena (
16). Our patient fulfilled all diagnostic criteria of disseminated BCG infection, including presence
Mycobacterium bovis BCG substrain on his skin as indicated by PCR, showing typical histopathological changes with granulomatous inflammation and positive tuberculosis complex-PCR in gastric washing, having systemic symptoms and more than two areas of involvement beyond the site of BCG vaccination (hepatosplenomegaly, pulmonary and skin involvement) (
3,
17). Patients with unrecognized primary immunodeficiency frequently experience severe complications of live bacterial or viral vaccines (for example BCG and rotavirus) in early infancy. Unusual vaccine adverse events could be the first signs of primary immune deficiencies (
2,
3,
8,
12,
17); some authors have estimated the incidence of primary immune deficiencies from unusual systemic adverse events of live vaccines in early infancy (
2). These complications may partly be the consequence of lack of standard newborn screening programs for primary immunodeficiency. Additionally, inattention to dubious infant death in the family history may also contribute to the late diagnosis and treatment of primary illness. Skin lesions like diffuse hyperpigmented maculopapular rash and subcutaneous nodules could be the primary manifestations of disseminated BCG disease in patients with PID. The cumulative incidence of PID according to a more recent report of Iranian Primary Immunodeficiency Registry (IPIDR) is about 9.7 per 1,000,000 individuals during the last seven years. Among different types of PID, severe combined immunodeficiency was the most common specific disorder (in about 21.1%; consisting of 154 cases from a total of 731 PID patients). This means a ratio of about one fifth from the total cases of PID who are at increased risk for serious adverse events of BCG vaccination at birth. In fact, more than one third of patients with PID should be considered susceptible to BCG because of susceptibility of infants and children with congenital phagocytic disorder (with prevalence of about 17.4%) to develop systemic BCG disease (
18). According to this report systemic BCG disease was found in 17 cases (2.3 %) as the first presentation of PID, during the last seven years (2006 to 2013) (
18). Considering the numerous recent reports of serious systemic adverse events of BCG vaccination (
5,
7,
10-
12,
19-
21) and also based on experience in our referral tertiary center, the probability of greater incidence of these side effects as a result of primary immune deficiency comes to mind. Thus, an additional local surveillance system designed to evaluate serious adverse events after live viral and bacterial vaccines at infection wards may be helpful to establish a databank and develop research protocols for clinical evaluation, diagnosis, and management of these adverse events in infants with PID in Iran.