H syndrome with low bone mineral density associated with hypovitaminosis D and low insulin-like growth factor 1

Rheumatological manifestations of H syndrome

H syndrome (HS) is a rare autosomal recessive genodermatosis characterised by cutaneous hyperpigmentation, hypertrichosis, sclerodermatous thickening, and multisystemic involvement. It results from mutations in the SLC29A3 gene encoding the human equilibrative nucleoside transporter 3, leading to impaired histiocyte apoptosis and unchecked proliferation. We report the case of a 24-year-old Moroccan male who had a history of insulin-dependent diabetes mellitus. He developed hyperpigmented skin patches with hypertrichosis and induration. Musculoskeletal findings included bilateral hallux valgus, pes planus, reducible flexion contractures of the proximal interphalangeal joints, and restricted ankle dorsiflexion. Additional findings consist of lymphadenopathy, hepatomegaly, hypogonadism, and ophthalmic manifestations. Investigations showed elevated sedimentation rate, anaemia, and osteopaenia. Ankle ultrasound revealed calcaneal enthesopathy and subcutaneous infiltration. In reporting this case, we aim to highlight the significant rheumatological involvement that can arise in patients with H syndrome and explore potential treatment options to improve the musculoskeletal findings.

Cases with the H syndrome presenting with skin and bone findings

BACKGROUND

The H syndrome is an autosomal recessive disease characterized by hyperpigmentation, hypertrichosis and sensorineural hearing loss.

METHODS

A mutation in the coding of the human equilibrative nucleoside transporter 3 (hENT3) within the SLC29A3 gene on chromosome 10q22 leads to the manifestation of this disease. In this report, we present two cases of H syndrome.

RESULTS

The first patient exhibits hyperpigmentation, hypogonadism, Type 1 diabetes mellitus, arthritis and osteoporosis. The second patient experiences hyperpigmentation, hypertrichosis, osteopenia and hypogonadism.

CONCLUSION

Our objective is to broaden the clinical spectrum of H syndrome, highlighting the involvement of arthritis, hyperinflammation and low bone mineral density in individuals with this disorder.

H Syndrome: Report of The First Case in African Ethnicity

H syndrome is an autosomal recessive multisystemic disease with a very low prevalence rate, characterized by indurated cutaneous hyperpigmentation, hypertrichosis, and various systemic manifestations. The syndrome is caused by mutations in SLC29A3 gene on chromosome 10q23, encoding for human equilibrative transporter 3 (hENT3). So far, only 100-120 patients with H syndrome have been described in the literature, with predominance among Indian, North-American, and Arab ethnicities.

This case report describes the first one of H-syndrome rarities in African ethnicity, a 30-year-old Sudanese male misdiagnosed with rheumatoid arthritis. The patient exhibited more than 90% of the clinical characteristics of H syndrome including obesity, short stature, characteristic hyperpigmented, sclerotic cutaneous plaques with induration and hypertrichosis, inflammatory arthropathy, hallux valgus, flexion deformity of toes, exophthalmos, cardiac anomaly, hypogonadism, and splenomegaly and characteristic histologic findings of dermal fibrosis, histiocytosis, lymphoid aggregation, and vascular proliferation.

H syndrome is an extremely rare autoinflammatory condition that has a complex constellation of pleiotropic manifestations with multisystemic involvement. And while further identification and better pathophysiological understanding of H syndrome are needed, physicians worldwide should be vigilant about the overlapping features of H syndrome with many other rheumatological, cutaneous, and genetic diseases.