Severe bullous eruption; It was reported in a published article title as stated below that a life-threatening episodes of mast cell activation can occur in diffuse cutaneous mastocytosis (DCM), a rare form of pediatric mastocytosis with reported incidence of 1-8%. Bullous eruptions in DCM have been reported after trauma, infections and medication administration. The article presented a child with generalized bullous eruption after routine vaccination. A 5-month-old child received scheduled vaccination with Rotavirus Vaccine, Live, Oral, Pentavalent (ROTATEQ) Orally (dose, frequency, lot number and expiration date were not reported) and Hemophilus influenzae B, conjugated pneumococcal vaccine (PCV), poliomyelitis (inactivated), and diphtheria and tetanus toxoid (dose, route, frequency, lot number and expiration date were not reported). Total and mature tryptase levels and skin pathology were evaluated. The patient was diagnosed with DCM at 3 months based on the peau d’orange appearance of his skin with positive Darier sign. Total tryptase was 64 with mature fraction of 3.1, urinary histamine 873 creatinine. Skin biopsy revealed a patchy band-like infiltrate of mononuclear cells in the dermis positive for tryptase and CD117. Therapy with H1 and H2-antagonists and topical sodium cromoglycate was initiated. A day after his routine vaccination at 5 months, he developed systemic generalized life-threatening symptoms with clear-fluid-filled blisters associated with nausea, vomiting, fevers and generalized malaise. A 5-day course of 0.5 mg/kg oral steroids led to complete resolution with no residual skin changes. Vaccinations are an under-recognized trigger for blistering in children with DCM. Premedication and vaccine administration on one-at-a-time basis may reduce the severity. Systemic steroids improve outcomes. Bullous eruption was considered to be life-threatening by the authors. Follow up information was received. A 5-month-old boy presented for evaluation of a raised apparently pruritic rash with episodic blisters. He was the product of an uncomplicated, full-term pregnancy with normal delivery. At 2 months of age, the skin of his abdomen and back became progressively rough and stiff with wheal formation surrounded by “raw” red areas of flare at the site of physical stroking. Skin biopsy was obtained from the right flank to confirm a suspected diagnosis of diffuse cutaneous mastocytosis (DCM). Review of systems was noteworthy for history of colicky abdominal pain. There was no history of wheezing, loss of consciousness, diarrhea, vomiting, or abdominal distention. He was following his growth curve and reached all age-appropriate developmental milestones. Physical examination on an unspecified date showed an alert, well-appearing boy in no evident distress, appropriately interactive. No lymphadenopathy or organomegaly was observed. Skin was notable for confluent skin-colored papules and plaques with peau d’orange appearance covering his trunk with urtication on minimal touch . Hyperpigmented patches of several centimeters in diameter were present on the extremities. On an unknown date, Laboratory results showed a 24-hour collection urinary histamine level of 873 microgram/gram creatinine. (reference range <35 microgram/gram creatinine), total serum tryptase of 64 nanogram/milliliter (ng/ml) (reference range<15 ng/mL), and mature tryptase of 3.1 ng/mL (reference range, <1 ng/mL). Blood cell counts on an unknown date were 12000 white blood cells/micro liter, 4690 red blood cells/microliter, and 473000 platelets/microliter with mild eosinophilia of 550 microliter, and otherwise normal differential. On an unknown date, Liver function tests were normal (alanine aminotransferase, 23 micro kat/Liter; aspartate aminotransferase, 34 micro kat/L). Lesional skin biopsy on an unknown date showed a patchy band-like infiltrate of mononuclear cells in the superficial dermis. lmmunostaining for tryptase and CD117 on an unknown date was positive, confirming that the infiltrate primarily consisted of mast cells. The diagnosis of DCM was made on the basis of these clinical and histopathologic findings. At 5 months of age, on an unknown date, the patient received his scheduled 4-month vaccinations with rotavirus vaccine, live, oral, pentavalent (ROTATEQ), diphtheria toxoid, pertussis vaccine (unspecified), tetanus toxoid, poliovirus vaccine inactivated (unspecified), pneumococcal conj vaccine (unspecified) and hib conj vaccine (unspecified carrier). Within 12 hours of vaccine administration, he became colicky. A day later, he began developing blisters filled with clear fluid that became confluent. The areas most affected included the back (which was covered with extensive bullae), skin fold areas of the upper arms, and the lower abdomen distant from the area of injection. He had no fever and was in no acute distress. He was treated with a 5-day course of low-dose oral steroids and recovered with no residual skin changes. A copy of the published article is attached as further documentation of the patient's experience. Literature Report: Follow up information has been received from the authors of a published literature article, titled as stated below. It was reported that the patient was vaccinated with Rotavirus Vaccine, Live, Oral, Pentavalent (ROTATEQ) Orally (dose, frequency, lot number and expiration date were not reported) and Hemophilus influenzae B, conjugated pneumococcal vaccine (PCV), poliomyelitis (inactivated), and diphtheria and tetanus toxoid at one visit concomitantly. Upon internal review, the event dermatitis bullous was determined to be medically significant. Literature Report: . It has been determined that case PL-009507513-2412POL007606 is a duplicate of case # US-MERCK-1205USA04644. Therefore, case # PL-009507513-2412POL007606 is being deleted from our files and the cases are consolidated into case # US-MERCK-1205USA04644. Additional information is not expected.; Sender's Comments: , MERCK1205USA04644:Mfr number