Sirolimus Restores Erythropoiesis and Controls Immune Dysregulation in a Child With Cartilage-Hair Hypoplasia: A Case Report

Anemia in patients with cartilage hair hypoplasia: a narrative review and recommendations

Cartilage hair hypoplasia (CHH) can lead to the development of anemia as a possible complication of this rare genetic disease. Despite various publications on anemia in CHH patients, a comprehensive review on this topic has not been conducted. This article reviews publications on anemia in CHH patients published from 1981 to 2022. Most authors have reported macrocytic anemia and blood transfusion as a common treatment approach in this patient group. Recommended guidelines for managing anemia in CHH patients include iron chelation therapy for those requiring multiple blood transfusions, regular assessment of anemia symptoms, red blood cell parameters, and immune system function. Future studies should evaluate the erythroid system in a larger cohort of CHH patients, considering key factors such as concurrent illnesses, age, height, and weight.

Shorter birth length and decreased T-cell production and function predict severe infections in children with non-severe combined immunodeficiency cartilage-hair hypoplasia

Background

Cartilage-hair hypoplasia (CHH) is a syndromic inborn error of immunity caused by variants in the RMRP gene. Disease manifestations vary, and their ability to predict outcome is uncertain. The optimal management of infants with CHH who do not fulfill classical severe combined immunodeficiency (SCID) criteria is unknown.

Objective

We described longitudinal changes in lymphocyte counts during childhood and explored correlations of early childhood clinical and laboratory features with clinical outcomes on long-term follow-up of CHH patients.

Methods

Immunologic laboratory parameters, birth length, the presence of Hirschsprung disease, and severe anemia correlated to the primary end points of respiratory and severe infections. We implemented traditional statistical methods and machine learning techniques.

Results

Thirty-two children with CHH were followed up for 2.7 to 22.1 years (median, 8.2 years, in total 331.3 patient-years). None of the patients had classical SCID. Median lymphocyte subclass counts, apart from CD16+/56+ cells, were subnormal throughout childhood, but did not show age-related decline seen in healthy children. Low immunoglobulin levels were uncommon and often transient. Respiratory and/or severe infections developed in 14 children, 8 of whom had low naive T-cell counts, absent T-cell receptor excision circles, and/or partial "leaky" SCID-level lymphopenia. Shorter birth length correlated with lower lymphocyte counts and the occurrence of infections. Of the laboratory parameters, decreased naive T-cell counts and abnormal lymphocyte proliferation responses contributed most to the development of severe infections. In addition, all participants with absent T-cell receptor excision circles developed severe infections. Opportunistic infections occurred only in children with leaky SCID-level lymphopenia.

Conclusions

Shorter birth length and a combination of laboratory abnormalities can predict the development of severe infections in children with CHH.