Cartilage-Hair Hypoplasia (CHH) Variant of Familial Metaphyseal Dysostosis

Familial metaphyseal dysostosis is an inherited defect with failure of proliferating cartilage. Two general types are recognized—the Jansen and the Schmidt, and there is reason to believe that a third “type” exists. While demonstrating certain features in common with the other two, this third variant, on the basis of clinical and roentgen criteria, is clearly a separate and distinct entity.

Case Report

A 6-year-old boy was referred to our Pediatric Clinic for evaluation of slow growth and diminished stature. A diagnosis of achondroplasia had been made at the age of four months. On admission to the Clinic his weight was 29 1b. and his height 36 in. Occasional diarrhea and gastrointestinal symptoms suggested a malabsorption-like picture. Physical examination was entirely normal except for arm and leg lengths which were disproportionately shortened in comparison to trunk measurements. Marked sparseness of thin blond hair on the scalp was noted. Eyebrows and body hair were also sparse, thin, and blond (Fig. 1).

A complete skeletal survey showed normal skull, chest, spine, trunk, and pelvis with a bone age of three and one-half years. Abnormal findings were limited to the long tubular bones. Bowing of the femurs was noted, along with a widened epiphyseal plate (Fig. 2). Metaphyseal fraying, irregularity, and fragmentation were seen. The metaphyseal margin was sharp and easily identified (Fig. 3).

A diagnosis of metaphyseal dysostosis was made.

Discussion

The term metaphyseal dysostosis is a misnomer for, rather than being a true metaphyseal defect, it is epiphyseal; neither is it a dysostosis but is, rather, a chondroplasia (7). The Jansen type is extremely rare, with only 6 reported cases. Deformity and early death are usual. The Schmidt or “tarda” type is a milder defect, generally with exclusive involvement of the long bones of the arms and legs. Variants with features of both types have been reported by several authors (2).

McKusick et al. (4) in a recent review of 77 dwarfs encountered among the Amish in Pennsylvania, mention a group with sparse thin hair in addition to small stature and roentgenographic findings typical of metaphyseal dysostosis. They chose to call this variant cartilage-hair hypoplasia (CHH). All patients had sparse, thin, light-colored hair with similar changes in the eyebrows and body hair, as well as roentgen findings typical of metaphyseal dysostosis and retarded bone age. Intestinal disorders resembling the malabsorption syndrome and megacolon were common.

Our patient showed defects in hair formation, retarded bone age, a sprue-like syndrome,and defects in the metaphyses of the long tubular bones. In no single case of metaphyseal dysostosis we were able to review (3, 5, 6) were all these clinical features mentioned. Hair defect, bowel abnormalities, and retarded bone age are not noted.