Skin Signs Reveal Hidden Metabolic Disease in One in Four Children

The skin has long been called a window into the body’s internal chemistry, but few studies have quantified just how informative that window can be for children with rare inherited metabolic disorders. A new retrospective cohort study from Ankara University’s Department of Pediatric Metabolism, published in the Archives of Dermatological Research, now offers one of the most detailed pictures to date. Among 1,012 patients followed for inherited metabolic disorders between 2012 and 2025, nearly one in four—24.9 percent, or 252 children—showed dermatological involvement of some kind. The finding suggests that skin examination, often treated as an afterthought in metabolic clinics, may deserve a far more central role in both diagnosis and long-term monitoring of these complex, lifelong conditions.

Inherited metabolic disorders, or IMDs, are a heterogeneous group of rare genetic diseases in which enzymatic defects disrupt the body’s normal biochemical pathways. Individually they are uncommon, but collectively they represent a significant burden of chronic disease in pediatrics, often affecting the nervous system, liver, heart, and skeleton. Because these disorders are multisystemic by nature, patients typically require lifelong surveillance by metabolic specialists. The Ankara team, led by Merve Koç Yekedüz and colleagues, reasoned that if metabolic dysfunction leaves fingerprints anywhere, it should be in the skin—the body’s largest organ and a tissue in constant, visible dialogue with circulating metabolites, hormones, and nutrients.

The researchers systematically reviewed medical records of all 1,012 IMD patients followed at their center over a thirteen-year period, extracting demographic, biochemical, and clinical data for those with documented skin findings. Dermatological manifestations were categorized and analyzed according to IMD subtype, and representative cases were photographed with informed consent, creating a visual atlas of what metabolic disease actually looks like on the skin. The cohort with skin involvement had a median age of 7.7 years, with a slight male predominance of 53.2 percent. Descriptive statistics were then used to map frequency patterns across diagnostic categories, revealing striking differences in how often each metabolic subgroup announced itself through the skin.

The three most skin-active diagnostic groups were aminoacidopathies, which accounted for 22.2 percent of dermatological cases, biotinidase deficiency at 19.4 percent, and lysosomal and peroxisomal storage disorders at 13.1 percent. Aminoacidopathies—conditions such as phenylketonuria, maple syrup urine disease, and hereditary tyrosinemia—arise when the body cannot properly break down particular amino acids, allowing intermediate metabolites to accumulate to toxic levels. Biotinidase deficiency impairs the recycling of biotin, a vitamin cofactor essential to several carboxylase enzymes, and has previously been reported to cause skin rashes and alopecia that resolve dramatically with biotin supplementation. Storage disorders, meanwhile, reflect the progressive accumulation of undegraded substrates inside cellular lysosomes or peroxisomes, with consequences that extend to connective tissue and skin structure.

By far the most common lesion type in the cohort was the eczematous or inflammatory eruption, seen in 66.1 percent of patients with skin involvement. This dominance of nonspecific inflammatory dermatitis is clinically important because it cuts both ways: it means many rashes in metabolic patients will look ordinary, but it also means that persistent, treatment-resistant eczema in a child with developmental delay, seizures, or unexplained biochemical abnormalities should prompt consideration of an underlying metabolic cause. The study also catalogued a remarkable range of more distinctive findings—persistent Mongolian spots, hyperpigmentation, hypopigmentation, hypertrichosis, xanthomas, ichthyosis, total alopecia, nail dystrophies, vascular lesions, structural anomalies such as inverted nipples and lipodystrophy, and reduced skin elasticity.

Several of these signs carry genuine diagnostic weight when interpreted through a metabolic lens. Extensive or persistently located Mongolian spots, for example, have been associated with lysosomal storage diseases in prior pediatric literature, and their presence in an infant with other subtle features can accelerate referral for enzymatic testing. Xanthomas—yellowish lipid deposits in the skin and tendons—point toward disorders of cholesterol metabolism such as homozygous familial hypercholesterolemia or Tangier disease. Ichthyosiform scaling raises the possibility of conditions like Chanarin-Dorfman syndrome, a neutral lipid storage disease that can present with different forms of erythrokeratoderma. Pigmentary changes connect to aminoacidopathies: in phenylketonuria, deficient tyrosine availability for melanin synthesis produces the classic fair hair and pale skin, and animal studies have shown that hypopigmentation can even be reversed by restoring the missing enzymatic function.

Perhaps the most nuanced insight from the Ankara cohort is that not every skin finding reflects the underlying genetic defect. A substantial proportion of dermatological manifestations were secondary to treatment itself—particularly the restrictive diets that form the backbone of therapy for many IMDs. Protein or carbohydrate limitation, essential for preventing toxic metabolite accumulation in conditions like urea cycle disorders and branched-chain organic acidemias, can nonetheless deprive the skin of adequate nutrients and trigger its own cutaneous pathology. The literature describes acrodermatitis dysmetabolica, a painful, eroded rash resembling zinc deficiency, in infants with maple syrup urine disease and phenylketonuria, typically flaring when metabolic control slips. Distinguishing disease-driven from diet-driven skin changes is therefore a practical skill that can directly alter clinical management.

The study’s authors argue that dermatological evaluation should become an integral part of routine care for IMD patients, and the data give that recommendation concrete force. Skin findings can serve as early diagnostic cues—sometimes appearing before neurological or systemic manifestations—and can also function as visible indicators of treatment efficacy, since resolving rashes, regrowing hair, or normalizing pigmentation may signal that biochemical control has been achieved. For a field in which diagnosis often hinges on expensive enzymatic assays and genetic sequencing, a careful physical examination of the skin remains one of the cheapest, fastest, and most accessible diagnostic instruments available. The researchers also documented representative cases photographically, building a visual reference that could help clinicians elsewhere recognize patterns they might otherwise miss.

The work builds on a growing body of literature mapping what has been called the clinical and biochemical footprints of inherited metabolic disease, including a 2021 review of metabolic dermatoses in Molecular Genetics and Metabolism. Prior case reports have linked congenital disorders of glycosylation to wrinkled skin and the so-called hanging fat sign, homocystinuria to pigmentary and vascular changes, prolidase deficiency to chronic lower-extremity ulcers, and mitochondrial dysfunction to a spectrum of dermatologic findings. What the Ankara study adds is scale: rather than isolated case reports, it provides cohort-level frequencies drawn from more than a thousand consecutively followed patients, allowing clinicians for the first time to appreciate how common skin involvement truly is across the IMD spectrum and which diagnostic subgroups are most likely to display it.

For practicing pediatricians and dermatologists, the message is straightforward. One out of four children with an inherited metabolic disorder will show something on their skin, and that something ranges from an ordinary-looking eczema to a highly specific sign like tendon xanthomas or ichthyosis. In a child already known to have an IMD, new skin findings warrant attention as possible markers of disease activity or dietary complications. In a child without a diagnosis, stubborn inflammatory eruptions combined with any systemic red flags should prompt metabolic screening rather than endless cycles of topical steroids. As genomic medicine continues to expand the recognized universe of metabolic disease, the humble skin examination—noninvasive, instantaneous, and free—may prove to be one of the most underused diagnostic tools in modern pediatrics, and this study makes a compelling case for putting it back at the center of the clinical encounter.

Subject of Research: Dermatological manifestations of inherited metabolic disorders in a pediatric cohort

Article Title: Cutaneous clues in inherited metabolic disorders: insights from a single-center cohort

Article References: Koç Yekedüz, M., Eminoğlu, F. T., Sürücü Kara, İ., Akyüzlüer Güneş, M. S., Kütükkiran, İ., & Köse, E. (2026). Cutaneous clues in inherited metabolic disorders: insights from a single-center cohort. Archives of Dermatological Research, 318(1), Article 428. https://doi.org/10.1007/s00403-026-04927-7

Image Credits: AI Generated

DOI: 10.1007/s00403-026-04927-7

Keywords: inherited metabolic disorders, dermatology, skin findings, aminoacidopathies, biotinidase deficiency, lysosomal storage disorders, eczema, hyperpigmentation, ichthyosis, pediatric metabolism, dietary restriction, rare disease