To observe the clinical efficacy and safety of low molecular weight heparin (LMWH) calcium injection combined with cimetidine (CIM) injection in the treatment of children with recurrent Henoch-Schönlein purpura (HSP).

Children with recurrent HSP were randomly divided into control group and treatment group. Both groups received conventional comprehensive treatment. The control group was administered 10 mg·kg^-1 of CIM injection for intravenous infusion, bid. The treatment group received subcutaneous injection of 100 IU·kg^-1 LMWH calcium injection in addition to control group’s regimen, qd. Both groups underwent continuous treatment for 14 days. Clinical efficacy, renal injury indicators, coagulation function parameters, immunoglobulin levels, T lymphocyte counts and inflammatory response markers were compared between the two groups, along with safety evaluation.

This clinical trial enrolled a total of 92 pediatric patients, with 46 cases each group. After treatment, the overall response rates were 78.26% (36 case/46 case) in control group and 93.48% (43 case /46 case) in treatment group; the urinary microalbumin (mALB) levels were (26.43±2.37) and (25.31±1.82) mg·L^-1, respectively; urinary α1-microglobulin (α1-MG) levels were (10.23±1.22) and (9.58±1.25) mg·L^-1, respectively; N-acetyl-β-D-glucosaminidase (NAG) levels were (16.32±1.12) and (15.70±1.18) U·L^-1, respectively; cystatin C (CysC) levels were (0.77±0.19) and (0.69±0.13) mg·L^-1, respectively; plasma D-dimer (D-Dimer) levels were (167.49±25.27) and (157.35±22.80) ng·mL^-1, respectively; fibrinogen (FIB) levels were (3.19±0.87) and (2.81±0.48) g·L^-1, respectively; prothrombin time (PT) were (11.44±1.19) and (12.17±1.52) s, respectively; the activated partial thromboplastin time (APTT) were (28.76±4.49) and (30.90±3.62) s, respectively; immunoglobulin A (IgA) levels were (2.35±0.56) and (2.08±0.59) g·L^-1, respectively; IgE levels were (74.74±9.64) and (71.04±7.78) IU·L^-1, respectively; IgG levels were (10.61±1.77) and (10.63±1.61) g·L^-1, respectively; IgM levels were (1.31±0.28) and (1.29±0.26) g·L^-1, respectively; CD4-positive T lymphocyte (CD4⁺) percentage were (37.89±4.92)% and (40.86±6.02)%, respectively; CD8⁺ percentage were (26.22±3.28)% and (24.55±3.01)%, respectively; CD4⁺/CD8⁺ ratio were 1.54±0.50 and 1.77±0.55, respectively; interferon-γ (IFN-γ) levels were (15.33±3.81) and (13.48±3.60) pg·mL^-1, respectively; interleukin-4 (IL-4) levels were (27.38±4.07) and (25.33±3.47) pg·mL^-1, respectively; interleukin-17 (IL-17) levels were (80.98±8.12) and (76.60±8.06) ng·L^-1, respectively. All these parameters in treatment group showed statistically significant differences compared to control group (P<0.05, P<0.01). The main adverse drug reactions in treatment group included injection site redness and swelling, fatigue and vomiting, while those in control group included nausea, dizziness and vomiting. The overall incidence of adverse drug reactions was 6.52% (3 cases/46 cases) in control group and 8.70% (4 cases/46 cases) in treatment group, with no statistically significant difference between the two groups (P>0.05).

The combination of LMWH calcium injections and CIM injections demonstrates superior efficacy in treating recurrent HSP in children, alleviating immune stress, exerting anti-inflammatory effects, and exhibiting safety profiles.